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<!DOCTYPE html>
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<h1 class="title">Intel® ISPC User's Guide</h1>
<p>The Intel® Implicit SPMD Program Compiler (Intel® ISPC) is a compiler for
writing SPMD (single program multiple data) programs to run on the CPU and GPU.
The SPMD
programming approach is widely known to graphics and GPGPU programmers; it
is used for GPU shaders and CUDA* and OpenCL* kernels, for example. The
main idea behind SPMD is that one writes programs as if they were operating
on a single data element (a pixel for a pixel shader, for example), but
then the underlying hardware and runtime system executes multiple
invocations of the program in parallel with different inputs (the values
for different pixels, for example).</p>
<p>The main goals behind <tt class="docutils literal">ispc</tt> are to:</p>
<ul class="simple">
<li>Build a variant of the C programming language that delivers good
performance to performance-oriented programmers who want to run SPMD
programs on CPUs and GPUs.</li>
<li>Provide a thin abstraction layer between the programmer and the
hardware--in particular, to follow the lesson from C for serial programs
of having an execution and data model where the programmer can cleanly
reason about the mapping of their source program to compiled assembly
language and the underlying hardware.</li>
<li>Harness the computational power of Single Program, Multiple Data (SIMD) vector
units without the extremely low-productivity task of directly writing
intrinsics.</li>
<li>Explore opportunities enabled by tight coupling between C/C++ application code
and SPMD <tt class="docutils literal">ispc</tt> code running on the same processor—lightweight function
calls between the two languages, direct data sharing via pointers without
copying or reformatting, etc.</li>
</ul>
<p><strong>We are very interested in your feedback and comments about ispc and
in hearing your experiences using the system. We are especially interested
in hearing if you try using ispc but see results that are not as you
were expecting or hoping for.</strong> We encourage you to send a note with your
experiences or comments to the <a class="reference external" href="https://github.com/ispc/ispc/discussions">GitHub Discussions</a> forum or to file bug or
feature requests with the <tt class="docutils literal">ispc</tt> <a class="reference external" href="https://github.com/ispc/ispc/issues?state=open">bug tracker</a>. (Thanks!)</p>
<p>Contents:</p>
<ul class="simple">
<li><a class="reference internal" href="#recent-changes-to-ispc">Recent Changes to ISPC</a><ul>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-31-0">Updating ISPC Programs For Changes In ISPC 1.31.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-30-0">Updating ISPC Programs For Changes In ISPC 1.30.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-29-0">Updating ISPC Programs For Changes In ISPC 1.29.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-28-0">Updating ISPC Programs For Changes In ISPC 1.28.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-27-0">Updating ISPC Programs For Changes In ISPC 1.27.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-26-0">Updating ISPC Programs For Changes In ISPC 1.26.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-25-0">Updating ISPC Programs For Changes In ISPC 1.25.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-24-0">Updating ISPC Programs For Changes In ISPC 1.24.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-23-0">Updating ISPC Programs For Changes In ISPC 1.23.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-22-0">Updating ISPC Programs For Changes In ISPC 1.22.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-21-0">Updating ISPC Programs For Changes In ISPC 1.21.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-20-0">Updating ISPC Programs For Changes In ISPC 1.20.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-19-0">Updating ISPC Programs For Changes In ISPC 1.19.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-18-0">Updating ISPC Programs For Changes In ISPC 1.18.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-17-0">Updating ISPC Programs For Changes In ISPC 1.17.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-16-0">Updating ISPC Programs For Changes In ISPC 1.16.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-15-0">Updating ISPC Programs For Changes In ISPC 1.15.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-14-1">Updating ISPC Programs For Changes In ISPC 1.14.1</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-14-0">Updating ISPC Programs For Changes In ISPC 1.14.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-13-0">Updating ISPC Programs For Changes In ISPC 1.13.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-12-0">Updating ISPC Programs For Changes In ISPC 1.12.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-11-0">Updating ISPC Programs For Changes In ISPC 1.11.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-10-0">Updating ISPC Programs For Changes In ISPC 1.10.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-9-2">Updating ISPC Programs For Changes In ISPC 1.9.2</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-9-1">Updating ISPC Programs For Changes In ISPC 1.9.1</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-9-0">Updating ISPC Programs For Changes In ISPC 1.9.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-8-2">Updating ISPC Programs For Changes In ISPC 1.8.2</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-7-0">Updating ISPC Programs For Changes In ISPC 1.7.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-6-0">Updating ISPC Programs For Changes In ISPC 1.6.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-5-0">Updating ISPC Programs For Changes In ISPC 1.5.0</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-3">Updating ISPC Programs For Changes In ISPC 1.3</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-2">Updating ISPC Programs For Changes In ISPC 1.2</a></li>
<li><a class="reference internal" href="#updating-ispc-programs-for-changes-in-ispc-1-1">Updating ISPC Programs For Changes In ISPC 1.1</a></li>
</ul>
</li>
<li><a class="reference internal" href="#getting-started-with-ispc">Getting Started with ISPC</a><ul>
<li><a class="reference internal" href="#installing-ispc">Installing ISPC</a></li>
<li><a class="reference internal" href="#compiling-and-running-a-simple-ispc-program">Compiling and Running a Simple ISPC Program</a></li>
</ul>
</li>
<li><a class="reference internal" href="#using-the-ispc-compiler">Using The ISPC Compiler</a><ul>
<li><a class="reference internal" href="#basic-command-line-options">Basic Command-line Options</a></li>
<li><a class="reference internal" href="#selecting-the-compilation-target">Selecting The Compilation Target</a></li>
<li><a class="reference internal" href="#selecting-32-or-64-bit-addressing">Selecting 32 or 64 Bit Addressing</a></li>
<li><a class="reference internal" href="#the-preprocessor">The Preprocessor</a></li>
<li><a class="reference internal" href="#pragma-directives">Pragma Directives</a></li>
<li><a class="reference internal" href="#debugging">Debugging</a></li>
<li><a class="reference internal" href="#optimization-settings">Optimization Settings</a></li>
<li><a class="reference internal" href="#other-ways-of-passing-arguments-to-ispc">Other ways of passing arguments to ISPC</a></li>
<li><a class="reference internal" href="#sample-based-profile-guided-optimization">Sample-Based Profile-Guided Optimization</a></li>
</ul>
</li>
<li><a class="reference internal" href="#using-ispc-as-a-library">Using ISPC as a Library</a><ul>
<li><a class="reference internal" href="#library-initialization">Library Initialization</a></li>
<li><a class="reference internal" href="#simple-compilation-interface">Simple Compilation Interface</a></li>
<li><a class="reference internal" href="#advanced-interface-with-ispcengine">Advanced Interface with ISPCEngine</a></li>
<li><a class="reference internal" href="#just-in-time-jit-compilation-interface">Just-In-Time (JIT) Compilation Interface</a></li>
<li><a class="reference internal" href="#compatibility">Compatibility</a></li>
<li><a class="reference internal" href="#cmake-integration">CMake Integration</a><ul>
<li><a class="reference internal" href="#basic-usage">Basic Usage</a></li>
<li><a class="reference internal" href="#cmake-variables">CMake Variables</a></li>
<li><a class="reference internal" href="#cmake-example">CMake Example</a></li>
</ul>
</li>
</ul>
</li>
<li><a class="reference internal" href="#the-ispc-parallel-execution-model">The ISPC Parallel Execution Model</a><ul>
<li><a class="reference internal" href="#basic-concepts-program-instances-and-gangs-of-program-instances">Basic Concepts: Program Instances and Gangs of Program Instances</a></li>
<li><a class="reference internal" href="#control-flow-within-a-gang">Control Flow Within A Gang</a><ul>
<li><a class="reference internal" href="#control-flow-example-if-statements">Control Flow Example: If Statements</a></li>
<li><a class="reference internal" href="#control-flow-example-loops">Control Flow Example: Loops</a></li>
<li><a class="reference internal" href="#gang-convergence-guarantees">Gang Convergence Guarantees</a></li>
</ul>
</li>
<li><a class="reference internal" href="#uniform-data">Uniform Data</a><ul>
<li><a class="reference internal" href="#uniform-control-flow">Uniform Control Flow</a></li>
<li><a class="reference internal" href="#uniform-variables-and-varying-control-flow">Uniform Variables and Varying Control Flow</a></li>
</ul>
</li>
<li><a class="reference internal" href="#data-races-within-a-gang">Data Races Within a Gang</a></li>
<li><a class="reference internal" href="#tasking-model">Tasking Model</a></li>
</ul>
</li>
<li><a class="reference internal" href="#the-ispc-language">The ISPC Language</a><ul>
<li><a class="reference internal" href="#relationship-to-the-c-programming-language">Relationship To The C Programming Language</a></li>
<li><a class="reference internal" href="#lexical-structure">Lexical Structure</a><ul>
<li><a class="reference internal" href="#integer-literals">Integer Literals</a></li>
<li><a class="reference internal" href="#floating-point-literals">Floating Point Literals</a></li>
<li><a class="reference internal" href="#string-literals">String Literals</a></li>
</ul>
</li>
<li><a class="reference internal" href="#types">Types</a><ul>
<li><a class="reference internal" href="#basic-types-and-type-qualifiers">Basic Types and Type Qualifiers</a></li>
<li><a class="reference internal" href="#signed-and-unsigned-integer-types">Signed and Unsigned Integer Types</a></li>
<li><a class="reference internal" href="#uniform-and-varying-qualifiers">"uniform" and "varying" Qualifiers</a></li>
<li><a class="reference internal" href="#defining-new-names-for-types">Defining New Names For Types</a></li>
<li><a class="reference internal" href="#pointer-types">Pointer Types</a></li>
<li><a class="reference internal" href="#function-pointer-types">Function Pointer Types</a></li>
<li><a class="reference internal" href="#reference-types">Reference Types</a></li>
<li><a class="reference internal" href="#enumeration-types">Enumeration Types</a></li>
<li><a class="reference internal" href="#short-vector-types">Short Vector Types</a></li>
<li><a class="reference internal" href="#array-types">Array Types</a></li>
<li><a class="reference internal" href="#struct-types">Struct Types</a><ul>
<li><a class="reference internal" href="#operators-overloading">Operators Overloading</a></li>
</ul>
</li>
<li><a class="reference internal" href="#structure-of-array-types">Structure of Array Types</a></li>
</ul>
</li>
<li><a class="reference internal" href="#declarations-and-initializers">Declarations and Initializers</a></li>
<li><a class="reference internal" href="#attributes">Attributes</a><ul>
<li><a class="reference internal" href="#noescape">noescape</a></li>
<li><a class="reference internal" href="#address-space">address_space</a></li>
<li><a class="reference internal" href="#unmangled">unmangled</a></li>
<li><a class="reference internal" href="#external-only">external_only</a></li>
<li><a class="reference internal" href="#deprecated">deprecated</a></li>
<li><a class="reference internal" href="#aligned">aligned</a></li>
</ul>
</li>
<li><a class="reference internal" href="#expressions">Expressions</a><ul>
<li><a class="reference internal" href="#dynamic-memory-allocation">Dynamic Memory Allocation</a></li>
<li><a class="reference internal" href="#type-casting">Type Casting</a></li>
</ul>
</li>
<li><a class="reference internal" href="#control-flow">Control Flow</a><ul>
<li><a class="reference internal" href="#conditional-statements-if">Conditional Statements: "if"</a></li>
<li><a class="reference internal" href="#conditional-statements-switch">Conditional Statements: "switch"</a></li>
<li><a class="reference internal" href="#iteration-statements">Iteration Statements</a><ul>
<li><a class="reference internal" href="#basic-iteration-statements-for-while-and-do">Basic Iteration Statements: "for", "while", and "do"</a></li>
<li><a class="reference internal" href="#iteration-over-active-program-instances-foreach-active">Iteration over active program instances: "foreach_active"</a></li>
<li><a class="reference internal" href="#iteration-over-unique-elements-foreach-unique">Iteration over unique elements: "foreach_unique"</a></li>
<li><a class="reference internal" href="#parallel-iteration-statements-foreach-and-foreach-tiled">Parallel Iteration Statements: "foreach" and "foreach_tiled"</a></li>
<li><a class="reference internal" href="#parallel-iteration-with-programindex-and-programcount">Parallel Iteration with "programIndex" and "programCount"</a></li>
</ul>
</li>
<li><a class="reference internal" href="#unstructured-control-flow-goto">Unstructured Control Flow: "goto"</a></li>
<li><a class="reference internal" href="#coherent-control-flow-statements-cif-and-friends">"Coherent" Control Flow Statements: "cif" and Friends</a></li>
<li><a class="reference internal" href="#functions-and-function-calls">Functions and Function Calls</a><ul>
<li><a class="reference internal" href="#function-overloading">Function Overloading</a></li>
</ul>
</li>
<li><a class="reference internal" href="#re-establishing-the-execution-mask">Re-establishing The Execution Mask</a></li>
<li><a class="reference internal" href="#task-parallel-execution">Task Parallel Execution</a><ul>
<li><a class="reference internal" href="#task-parallelism-launch-and-sync-statements">Task Parallelism: "launch" and "sync" Statements</a></li>
<li><a class="reference internal" href="#task-parallelism-runtime-requirements">Task Parallelism: Runtime Requirements</a></li>
</ul>
</li>
</ul>
</li>
<li><a class="reference internal" href="#llvm-intrinsic-functions">LLVM Intrinsic Functions</a></li>
<li><a class="reference internal" href="#function-templates">Function Templates</a></li>
</ul>
</li>
<li><a class="reference internal" href="#the-ispc-standard-library">The ISPC Standard Library</a><ul>
<li><a class="reference internal" href="#basic-operations-on-data">Basic Operations On Data</a><ul>
<li><a class="reference internal" href="#logical-and-selection-operations">Logical and Selection Operations</a></li>
<li><a class="reference internal" href="#bit-operations">Bit Operations</a></li>
</ul>
</li>
<li><a class="reference internal" href="#math-functions">Math Functions</a><ul>
<li><a class="reference internal" href="#basic-math-functions">Basic Math Functions</a></li>
<li><a class="reference internal" href="#transcendental-functions">Transcendental Functions</a></li>
<li><a class="reference internal" href="#saturating-arithmetic">Saturating Arithmetic</a></li>
<li><a class="reference internal" href="#dot-product">Dot product</a></li>
<li><a class="reference internal" href="#intel-amx-advanced-matrix-extensions">Intel AMX (Advanced Matrix Extensions)</a></li>
<li><a class="reference internal" href="#pseudo-random-numbers">Pseudo-Random Numbers</a></li>
<li><a class="reference internal" href="#random-numbers">Random Numbers</a></li>
</ul>
</li>
<li><a class="reference internal" href="#output-functions">Output Functions</a></li>
<li><a class="reference internal" href="#assertions">Assertions</a></li>
<li><a class="reference internal" href="#compiler-optimization-hints">Compiler Optimization Hints</a></li>
<li><a class="reference internal" href="#cross-program-instance-operations">Cross-Program Instance Operations</a><ul>
<li><a class="reference internal" href="#reductions">Reductions</a></li>
</ul>
</li>
<li><a class="reference internal" href="#stack-memory-allocation">Stack Memory Allocation</a></li>
<li><a class="reference internal" href="#data-movement">Data Movement</a><ul>
<li><a class="reference internal" href="#setting-and-copying-values-in-memory">Setting and Copying Values In Memory</a></li>
<li><a class="reference internal" href="#packed-load-and-store-operations">Packed Load and Store Operations</a></li>
<li><a class="reference internal" href="#streaming-load-and-store-operations">Streaming Load and Store Operations</a></li>
</ul>
</li>
<li><a class="reference internal" href="#data-conversions">Data Conversions</a><ul>
<li><a class="reference internal" href="#converting-between-array-of-structures-and-structure-of-arrays-layout">Converting Between Array-of-Structures and Structure-of-Arrays Layout</a></li>
<li><a class="reference internal" href="#conversions-to-and-from-half-precision-floats">Conversions To and From Half-Precision Floats</a></li>
<li><a class="reference internal" href="#converting-from-to-srgb8">Converting from/to sRGB8</a></li>
</ul>
</li>
<li><a class="reference internal" href="#systems-programming-support">Systems Programming Support</a><ul>
<li><a class="reference internal" href="#atomic-operations-and-memory-fences">Atomic Operations and Memory Fences</a></li>
<li><a class="reference internal" href="#prefetches">Prefetches</a></li>
<li><a class="reference internal" href="#system-information">System Information</a></li>
</ul>
</li>
</ul>
</li>
<li><a class="reference internal" href="#interoperability-with-the-application">Interoperability with the Application</a><ul>
<li><a class="reference internal" href="#interoperability-overview">Interoperability Overview</a></li>
<li><a class="reference internal" href="#data-layout">Data Layout</a></li>
<li><a class="reference internal" href="#data-alignment-and-aliasing">Data Alignment and Aliasing</a></li>
<li><a class="reference internal" href="#restructuring-existing-programs-to-use-ispc">Restructuring Existing Programs to Use ISPC</a></li>
</ul>
</li>
<li><a class="reference internal" href="#notices-disclaimers">Notices & Disclaimers</a></li>
</ul>
<div class="section" id="recent-changes-to-ispc">
<h1>Recent Changes to ISPC</h1>
<p>See the file <a class="reference external" href="https://raw.github.com/ispc/ispc/main/docs/ReleaseNotes.txt">ReleaseNotes.txt</a> in the <tt class="docutils literal">ispc</tt> distribution for a list
of recent changes to the compiler.</p>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-31-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.31.0</h2>
<p>ISPC Targets:</p>
<ul class="simple">
<li>New <tt class="docutils literal"><span class="pre">avx10.2nvl-x4</span></tt>, <tt class="docutils literal"><span class="pre">avx10.2nvl-x8</span></tt>, <tt class="docutils literal"><span class="pre">avx10.2nvl-x16</span></tt>,
<tt class="docutils literal"><span class="pre">avx10.2nvl-x32</span></tt>, and <tt class="docutils literal"><span class="pre">avx10.2nvl-x64</span></tt> targets have been added for Intel
Nova Lake processors. These targets implement AVX10.2 and APX (Advanced
Performance Extensions) but, unlike the <tt class="docutils literal">avx10.2dmr</tt> (Diamond Rapids)
targets, they do not include AMX. The corresponding predefined macro is
<tt class="docutils literal">ISPC_TARGET_AVX10_2NVL</tt>.</li>
<li>The multi-target runtime dispatcher now selects an AMX-bearing server target
variant (<tt class="docutils literal">avx512spr</tt>, <tt class="docutils literal">avx512gnr</tt>, <tt class="docutils literal">avx10.2dmr</tt>) only when the system
supports AMX, instead of relying solely on the ISA ordering.</li>
</ul>
<p>New Options:</p>
<ul class="simple">
<li>A new <tt class="docutils literal"><span class="pre">--opt=disable-apx[=<list>]</span></tt> option allows disabling x86 APX
(Advanced Performance Extensions) sub-features, which are enabled by default
on APX-capable targets such as <tt class="docutils literal">avx10.2dmr</tt> and <tt class="docutils literal">avx10.2nvl</tt>. With no
list it disables all APX sub-features; otherwise it accepts a comma-separated
subset of <tt class="docutils literal">egpr</tt>, <tt class="docutils literal">ndd</tt>, <tt class="docutils literal">push2pop2</tt>, <tt class="docutils literal">ppx</tt>, <tt class="docutils literal">ccmp</tt>, <tt class="docutils literal">cf</tt>,
<tt class="docutils literal">nf</tt>, <tt class="docutils literal">zu</tt>, and <tt class="docutils literal">jmpabs</tt>.</li>
</ul>
<p>Windows x64 Stack Unwinding For APX:</p>
<ul class="simple">
<li>On Windows x64, code that uses the APX extended general purpose registers
(<tt class="docutils literal">egpr</tt>, R16-R31) cannot be described by the legacy v1/v2 SEH unwind
encodings, which have no register-number field for registers beyond R15.
When targeting Windows on an APX-capable target (the <tt class="docutils literal">avx10.2dmr</tt> and
<tt class="docutils literal">avx10.2nvl</tt> families) with <tt class="docutils literal">egpr</tt> enabled, ISPC now automatically
requests Windows x64 unwind information version 3. If you need
compatibility with an older unwinder, disable the extended registers with
<tt class="docutils literal"><span class="pre">--opt=disable-apx=egpr</span></tt>, which also drops the unwind v3 request.</li>
</ul>
<p>New Features:</p>
<ul class="simple">
<li>Implementation of two new fast-math modes: <tt class="docutils literal">balanced</tt> and <tt class="docutils literal">aggressive</tt>.
These modes bring more aggressive optimizations compared to the default
<tt class="docutils literal">legacy</tt> mode. The latter was the mode provided so far in previous ISPC
versions. It is still available and left unchanged. The fast-math mode can be
specified with the option <tt class="docutils literal"><span class="pre">--opt=fast-math:<mode></span></tt>. See the optimization
settings section for more information about the new modes.</li>
</ul>
<p>Standard Library Changes:</p>
<ul class="simple">
<li><strong>Breaking change</strong>: <tt class="docutils literal">reduce_add()</tt> now returns the same type as its
input. Previously the signatures widened the result, but the
implementation was inconsistent and partially incorrect. The new
same-type convention also matches the prevailing convention in other
SIMD/SPMD ecosystems and is consistent with <tt class="docutils literal">reduce_min()</tt> /
<tt class="docutils literal">reduce_max()</tt> in ISPC. For overflow-safe accumulation, cast the
input to a wider type explicitly, e.g. <tt class="docutils literal"><span class="pre">reduce_add((int32)x)</span></tt> for an
<tt class="docutils literal">int16</tt> <tt class="docutils literal">x</tt>. Any code that relied on the previous widened return
type must be updated.</li>
<li>The Gauss error function <tt class="docutils literal">erf</tt> and the complementary error function <tt class="docutils literal">erfc</tt>
have been added to the standard library.</li>
<li>The <tt class="docutils literal">expm1</tt> function (meant to compute <tt class="docutils literal"><span class="pre">exp(x)-1</span></tt> accurately), and the
<tt class="docutils literal">log1p</tt> function (meant to compute <tt class="docutils literal">log(1+x)</tt> accurately) have also been
added to the standard library.</li>
<li>The hyperbolic functions <tt class="docutils literal">sinh</tt>, <tt class="docutils literal">cosh</tt> and <tt class="docutils literal">tanh</tt> have also been added
to the standard library.</li>
<li>The precision of several existing math functions has been improved, including
<tt class="docutils literal">asin</tt> (especially close to 0), <tt class="docutils literal">acos</tt>, <tt class="docutils literal">atan</tt> (which now also handles
<tt class="docutils literal"><span class="pre">-0</span></tt> correctly), and the default <tt class="docutils literal">log</tt>. As a result, the values these
functions return may differ slightly from previous ISPC versions. Code that
relies on bit-exact results (for example, golden-output comparisons) may need
to update its expected values.</li>
</ul>
<p>New Architecture Support:</p>
<ul class="simple">
<li>Initial support for the PowerPC 64-bit little-endian (ppc64le) architecture
has been added using generic targets (e.g., generic-i32x4). The baseline is
POWER ISA 2.7 (POWER8+) with VSX. This support is experimental and not
included in official ISPC binaries. To use it, build ISPC from source with
the <tt class="docutils literal">PPC64_ENABLED=ON</tt> CMake option. Usage: <tt class="docutils literal">ispc <span class="pre">--arch=ppc64le</span>
<span class="pre">--target=generic-i32x4</span> foo.ispc <span class="pre">-o</span> foo.o</tt>.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-30-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.30.0</h2>
<p>New Features:</p>
<ul class="simple">
<li>Intel AMX (Advanced Matrix Extensions) support has been added to the standard
library. AMX provides hardware acceleration for matrix operations, particularly
useful for machine learning workloads. The new <tt class="docutils literal"><amx.isph></tt> header provides
functions for tile configuration, data loading/storing, and matrix dot products
for INT8, BF16, and FP16 data types. AMX is supported on <tt class="docutils literal">avx512spr</tt>,
<tt class="docutils literal">avx512gnr</tt>, and <tt class="docutils literal">avx10.2dmr</tt> targets. Please refer to
<a class="reference internal" href="#intel-amx-advanced-matrix-extensions">Intel AMX (Advanced Matrix Extensions)</a> for more details.</li>
</ul>
<p>Language Changes:</p>
<ul class="simple">
<li>Integral type aliases (<tt class="docutils literal">size_t</tt>, <tt class="docutils literal">ptrdiff_t</tt>, <tt class="docutils literal">intptr_t</tt>, <tt class="docutils literal">uintptr_t</tt>)
can now be used as non-type template parameters.</li>
</ul>
<p>Deprecated Targets:</p>
<ul class="simple">
<li>The <tt class="docutils literal"><span class="pre">sse2-i32x4</span></tt> and <tt class="docutils literal"><span class="pre">sse2-i32x8</span></tt> targets are no longer deprecated. Based
on customer feedback indicating active use, we have decided to retain these
targets and removed the deprecation warning.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-29-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.29.0</h2>
<p>Language Changes:</p>
<p>The compiler now assumes that all loops with non-constant conditions will make
forward progress and eventually terminate. This enables optimizations based
on the assumption that loops will not execute indefinitely. Infinite loops
with constant conditions like <tt class="docutils literal">for <span class="pre">(;;)</span></tt> or <tt class="docutils literal">while (1)</tt> are treated
specially and do not have this assumption applied.</p>
<p>Compiler Switches:</p>
<ul class="simple">
<li>Added <tt class="docutils literal"><span class="pre">--profile-sample-use=<file></span></tt> to enable profile-guided optimization
using sample profile data. When provided, the ISPC compiler loads the
specified sample profile data file and uses it to guide optimization decisions
during compilation. Use with <tt class="docutils literal"><span class="pre">--sample-profiling-debug-info</span></tt> to generate
debug information optimized for sample-based profiling.</li>
<li>Added <tt class="docutils literal"><span class="pre">--[no-]internal-export-functions</span></tt> to control generation of internal
(ISPC-callable) versions of exported functions. The flag is enabled by default.
When disabled (<tt class="docutils literal"><span class="pre">--no-internal-export-functions</span></tt>), only external versions are
generated and calling exported functions from ISPC code will result in a
compilation error.</li>
<li>Added <tt class="docutils literal"><span class="pre">--stack-protector[=<level>]</span></tt> flag to enable Stack Smash Protection (SSP)
for ISPC functions, providing runtime detection of stack buffer overflows.
<tt class="docutils literal"><span class="pre">--stack-protector</span></tt> (equivalent to <tt class="docutils literal"><span class="pre">--stack-protector=on</span></tt>) enables stack
protectors for functions vulnerable to stack smashing. <tt class="docutils literal"><span class="pre">--stack-protector=strong</span></tt>
enables stack protectors for functions that contain arrays of any size or take
addresses of local variables. <tt class="docutils literal"><span class="pre">--stack-protector=all</span></tt> enables stack protectors
for all functions. <tt class="docutils literal"><span class="pre">--stack-protector=none</span></tt> disables stack protectors (default).</li>
<li>The default DWARF version has been updated to DWARF 5, matching the LLVM
default. If your debugging tools do not support DWARF 5, you can use the
<tt class="docutils literal"><span class="pre">--dwarf-version=<N></span></tt> flag to specify an earlier version.</li>
</ul>
<p>Warning for Exported Function Calls:</p>
<p>A new warning has been introduced to prepare for an upcoming behavior change in
exported functions. Currently, <tt class="docutils literal">export</tt> functions generate both internal
(ISPC-callable) and external (C/C++-callable) versions. Starting in ISPC 1.30,
the default behavior will change to generate only external versions, matching
the behavior of the <tt class="docutils literal">external_only</tt> attribute.</p>
<p>In ISPC 1.29, the compiler issues a <strong>warning</strong> when an exported function
without the <tt class="docutils literal">external_only</tt> attribute is called from ISPC code. This warning
helps identify code that may be affected by the upcoming change. To address
this warning, you can:</p>
<ul class="simple">
<li>Use a non-exported function for ISPC-to-ISPC calls</li>
<li>Add the <tt class="docutils literal">external_only</tt> attribute (see <a class="reference internal" href="#external-only">external_only</a>) to the function
(note: this will generate an <strong>error</strong> instead of a warning)</li>
<li>Use the <tt class="docutils literal"><span class="pre">--no-internal-export-functions</span></tt> command-line flag to suppress
internal version generation (note: this will generate <strong>errors</strong> instead of
warnings for all exported function calls)</li>
</ul>
<p>Note: The compiler can only detect calls to exported functions within the same
compilation unit. Cross-module calls to exported functions cannot be detected.</p>
<p>ISPC Targets:</p>
<ul class="simple">
<li>New <tt class="docutils literal"><span class="pre">avx512gnr-x4</span></tt>, <tt class="docutils literal"><span class="pre">avx512gnr-x8</span></tt>, <tt class="docutils literal"><span class="pre">avx512gnr-x16</span></tt>, <tt class="docutils literal"><span class="pre">avx512gnr-x32</span></tt>,
and <tt class="docutils literal"><span class="pre">avx512gnr-x64</span></tt> targets have been added for Intel Granite Rapids processors.
These targets support AVX-512 with AMX-FP16 capabilities.</li>
<li><tt class="docutils literal">avx10.2</tt> family of targets has been renamed to <tt class="docutils literal">avx10.2dmr</tt>. The macro
<tt class="docutils literal">ISPC_TARGET_AVX10_2</tt> has been replaced with <tt class="docutils literal">ISPC_TARGET_AVX10_2DMR</tt>.</li>
<li><tt class="docutils literal"><span class="pre">sse2-i32x4</span></tt> and <tt class="docutils literal"><span class="pre">sse2-i32x8</span></tt> targets are deprecated and will be removed in
future releases.</li>
<li><tt class="docutils literal"><span class="pre">gen9-x8</span></tt>, and <tt class="docutils literal"><span class="pre">gen9-x16</span></tt> targets have been removed.</li>
</ul>
<p>Predefined Macros:</p>
<ul class="simple">
<li>New predefined macros <tt class="docutils literal">ISPC_TARGET_HAS_FP16_SUPPORT</tt> and
<tt class="docutils literal">ISPC_TARGET_HAS_FP64_SUPPORT</tt> have been added following the consistent
naming convention used by other target capability macros. The old macro names
<tt class="docutils literal">ISPC_FP16_SUPPORTED</tt> and <tt class="docutils literal">ISPC_FP64_SUPPORTED</tt> remain available for
backward compatibility but are now deprecated.</li>
<li>The <tt class="docutils literal">ISPC_TARGET_AVX512GNR</tt> macro has been added.</li>
<li>The <tt class="docutils literal">ISPC_TARGET_AVX10_2</tt> macro has been replaced with
<tt class="docutils literal">ISPC_TARGET_AVX10_2DMR</tt> to match the target renaming.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-28-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.28.0</h2>
<p>New Features:</p>
<ul class="simple">
<li>Added a new command-line option <tt class="docutils literal"><span class="pre">--include-float16-conversions</span></tt>. This
option makes the compiler include float16 conversion functions in the
compiled module. This is useful for targets that do not have native
instructions for float16 conversions, such as x86 targets prior to AVX2.
This option is disabled by default.</li>
<li>ISPC can now generate nanobind wrappers for ISPC modules, allowing easy
and lightweight integration of ISPC code with Python. The generated wrappers
can be built into native Python modules and imported into Python code. The
<tt class="docutils literal"><span class="pre">--nanobind-wrapper=<filename></span></tt> command-line option enables this feature.</li>
<li>Struct operator overloading has been extended. Extended support for
overloading unary (<tt class="docutils literal">++</tt>, <tt class="docutils literal"><span class="pre">--</span></tt>, <tt class="docutils literal">-</tt>, <tt class="docutils literal">!</tt>, <tt class="docutils literal">~</tt>), binary (<tt class="docutils literal">*</tt>,
<tt class="docutils literal">/</tt>, <tt class="docutils literal">%</tt>, <tt class="docutils literal">+</tt>, <tt class="docutils literal">-</tt>, <tt class="docutils literal">>></tt>, <tt class="docutils literal"><<</tt>, <tt class="docutils literal">==</tt>, <tt class="docutils literal">!=</tt>, <tt class="docutils literal"><</tt>, <tt class="docutils literal">></tt>,
<tt class="docutils literal"><=</tt>, <tt class="docutils literal">>=</tt>, <tt class="docutils literal">&</tt>, <tt class="docutils literal">|</tt>, <tt class="docutils literal">^</tt>, <tt class="docutils literal">&&</tt>, <tt class="docutils literal">||</tt>), and assignment
(<tt class="docutils literal">=</tt>, <tt class="docutils literal">+=</tt>, <tt class="docutils literal"><span class="pre">-=</span></tt> , <tt class="docutils literal">*=</tt>, <tt class="docutils literal">/=</tt>, <tt class="docutils literal">%=</tt>, <tt class="docutils literal"><<=</tt>, <tt class="docutils literal">>>=</tt>, <tt class="docutils literal">&=</tt>,
<tt class="docutils literal">|=</tt>, <tt class="docutils literal">^=</tt>) operators for struct types.</li>
<li>ISPC can now be used as a C++ library (<tt class="docutils literal">libispc</tt>) for embedding ISPC
compilation directly into applications. It now also provides CMake
configuration files for easy integration into other CMake projects. The
library includes experimental Just-In-Time (JIT) compilation capabilities
for runtime code generation and execution. See the section
<a class="reference internal" href="#using-ispc-as-a-library">Using ISPC as a Library</a> for more details.</li>
<li>Added a new <tt class="docutils literal">include/intrinsics</tt> directory containing header files that
implement selected SSE intrinsics in ISPC. If you're porting existing code
from intrinsics to ISPC, you can use these headers as a reference.</li>
</ul>
<p>Language and Syntax Changes:</p>
<ul class="simple">
<li>Integer literals are now stricter:<ul>
<li>Limits the number of occurrences of <tt class="docutils literal">[uUlL]</tt> symbols (e.g., <tt class="docutils literal">ulll</tt>,
<tt class="docutils literal">uul</tt>, and <tt class="docutils literal">lulu</tt> are not valid anymore).</li>
<li>The value modification suffix (i.e., <tt class="docutils literal">[kMG]</tt>) must precede the type
modification suffix (i.e., <tt class="docutils literal">[uUlL]</tt> symbols).</li>
<li>Like C/C++, <tt class="docutils literal">lL</tt> and <tt class="docutils literal">Ll</tt> suffixes are no longer allowed (i.e., mixing
lower- and upper-case <tt class="docutils literal">L</tt> to form a <tt class="docutils literal">LL</tt> suffix).</li>
</ul>
</li>
</ul>
<p>Standard Library Changes:</p>
<ul>
<li><p class="first"><tt class="docutils literal">select</tt> functions now support unsigned integer types <tt class="docutils literal">uint8</tt>,
<tt class="docutils literal">uint16</tt>, <tt class="docutils literal">uint32</tt>, and <tt class="docutils literal">uint64</tt> as well as uniform short vectors.</p>
</li>
<li><p class="first">Added new functions: <tt class="docutils literal">isinf</tt>, <tt class="docutils literal">isfinite</tt>, and <tt class="docutils literal">srgb8_to_float</tt>.</p>
</li>
<li><p class="first">Standard library functions for short vectors have been moved to a separate
header file <tt class="docutils literal">short_vec.isph</tt>. They are no longer defined implicitly for
every file compiled with ISPC. Code using such functions should now include
this file with:</p>
<pre class="literal-block">
#include "short_vec.isph"
</pre>
</li>
<li><p class="first">Support for short vector types has been added to the following element-wise
functions: <tt class="docutils literal">fmod</tt>, <tt class="docutils literal">isnan</tt>, <tt class="docutils literal">rsqrt_fast</tt>, and <tt class="docutils literal">clamp</tt>.</p>
</li>
</ul>
<p>Debugging:</p>
<p>The default DWARF version was updated to DWARF 5. You can still
specify any supported DWARF version with the <tt class="docutils literal"><span class="pre">--dwarf-version=</span></tt> switch.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-27-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.27.0</h2>
<p>New targets:</p>
<p>New targets have been added for platforms supporting Intel® Advanced Vector
Extensions 10.2: <tt class="docutils literal"><span class="pre">avx10.2-x4</span></tt>, <tt class="docutils literal"><span class="pre">avx10.2-x8</span></tt>, <tt class="docutils literal"><span class="pre">avx10.2-x16</span></tt>,
<tt class="docutils literal"><span class="pre">avx10.2-x32</span></tt>, and <tt class="docutils literal"><span class="pre">avx10.2-x64</span></tt>. Additionally, a new macro
<tt class="docutils literal">ISPC_TARGET_AVX10_2</tt> has been introduced.</p>
<p>Standard library:</p>
<ul class="simple">
<li>Cross-lane operations - <tt class="docutils literal">broadcast</tt>, <tt class="docutils literal">rotate</tt>, <tt class="docutils literal">shift</tt>, and
<tt class="docutils literal">shuffle</tt> - are now supported for unsigned types.</li>
<li>ISPC's data handling capabilities have been extended to include signed and
unsigned <tt class="docutils literal">int8</tt> and <tt class="docutils literal">int16</tt> types in the reduction functions.</li>
<li>Support for <tt class="docutils literal">packed_load</tt> and <tt class="docutils literal">packed_store</tt> operations has also been
expanded to include: <tt class="docutils literal">int8</tt>, <tt class="docutils literal">int16</tt> (signed/unsigned), <tt class="docutils literal">float16</tt>,
<tt class="docutils literal">float</tt>, and <tt class="docutils literal">double</tt>.</li>
<li>The cube root function <tt class="docutils literal">cbrt</tt> has been added to the standard library for
<tt class="docutils literal">float</tt> and <tt class="docutils literal">double</tt> types.</li>
<li>Dot product functionality has been enhanced with mixed signedness support for
16-bit integers. The following input combinations are now supported: u16 x u16
(unsigned x unsigned), i16 x i16 (signed x signed), u16 x i16 (mixed
signedness). For consistency with other naming conventions, the function
<tt class="docutils literal">dot2add_i16_packed</tt> has been renamed to <tt class="docutils literal">dot2add_i16i16_packed</tt>.</li>
</ul>
<p>New standard library functions for short vectors:</p>
<p>The <tt class="docutils literal">max</tt>, <tt class="docutils literal">min</tt> and <tt class="docutils literal">abs</tt> functions for short vectors of basic types
have been added to the standard library. They support both uniform and varying
short vector types for all basic types supported by the corresponding standard
functions, i.e., signed and unsigned integer types and floating-point types.</p>
<p>It makes it possible, for example, to find the maximum value between two short
vectors:</p>
<pre class="literal-block">
uniform int<3> a = {1, 2, 3};
uniform int<3> b = {3, -2, 1};
uniform int<3> c = max(a, b); // c = {3, 2, 3}
varying float<4> x, y;
varying float<4> z = max(x, y);
</pre>
<p>Support for short vector types has also been added for the following
floating-point element-wise functions: <tt class="docutils literal">round</tt>, <tt class="docutils literal">floor</tt>, <tt class="docutils literal">ceil</tt>,
<tt class="docutils literal">trunc</tt>, <tt class="docutils literal">rcp</tt>, <tt class="docutils literal">rcp_fast</tt>, <tt class="docutils literal">sqrt</tt>, <tt class="docutils literal">rsqrt</tt>, <tt class="docutils literal">sin</tt>, <tt class="docutils literal">asin</tt>,
<tt class="docutils literal">cos</tt>, <tt class="docutils literal">acos</tt>, <tt class="docutils literal">tan</tt>, <tt class="docutils literal">atan</tt>, <tt class="docutils literal">exp</tt>, <tt class="docutils literal">log</tt>, <tt class="docutils literal">atan2</tt>, <tt class="docutils literal">pow</tt> and
<tt class="docutils literal">cbrt</tt>.</p>
<p>Language changes:</p>
<ul class="simple">
<li>The <tt class="docutils literal">aligned(N)</tt> attribute is now available to specify the alignment of
variables and struct types.</li>
<li>A bug was fixed where unsigned array indices or pointer arithmetic with
unsigned offsets could result in overflow due to sign extension when promoting
to pointer size. This issue is now resolved, and the compiler correctly
handles unsigned integer indexing and pointer arithmetic.</li>
</ul>
<p>Compiler flags changes:</p>
<ul class="simple">
<li>The <tt class="docutils literal"><span class="pre">-dD</span></tt> and <tt class="docutils literal"><span class="pre">-dM</span></tt> flags are now supported. They are useful for debugging the
preprocessor and checking the macros defined by the compiler.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-26-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.26.0</h2>
<p>There are breaking changes to ARM support:</p>
<ul class="simple">
<li>The <tt class="docutils literal"><span class="pre">--arch=arm</span></tt> flag, which previously mapped to ARMv7 (32-bit), now maps
to ARMv8 (32-bit). There are no changes to <tt class="docutils literal"><span class="pre">--arch=aarch64</span></tt>, which continues
to map to ARMv8 (64-bit).</li>
<li>The CPU definitions for the ARMv7 architecture have been removed:
<tt class="docutils literal"><span class="pre">cortex-a9</span></tt> and <tt class="docutils literal"><span class="pre">cortex-a15</span></tt>.</li>
<li>New CPU definitions have been introduced, including <tt class="docutils literal"><span class="pre">cortex-a55</span></tt>,
<tt class="docutils literal"><span class="pre">cortex-a78</span></tt>, <tt class="docutils literal"><span class="pre">cortex-a510</span></tt>, and <tt class="docutils literal"><span class="pre">cortex-a520</span></tt>, along with support for
new Apple devices.</li>
<li>New double-pumped targets have been introduced: <tt class="docutils literal"><span class="pre">neon-i16x16</span></tt> and
<tt class="docutils literal"><span class="pre">neon-i8x32</span></tt>.</li>
</ul>
<p>Language Updates:</p>
<ul class="simple">
<li>Macro definitions for the LLVM version that ISPC is based on have been added.
Please refer to <a class="reference internal" href="#the-preprocessor">The Preprocessor</a> for more details.</li>
<li>The <tt class="docutils literal"><span class="pre">__attribute__((deprecated))</span></tt> attribute can now be applied to a function
to mark it as deprecated, generating a warning when the function is called.</li>
</ul>
<p>Compiler flags changes:</p>
<ul class="simple">
<li>The <tt class="docutils literal"><span class="pre">--nocpp</span></tt> command-line flag is deprecated and will be removed in a
future release.</li>
<li>The target <tt class="docutils literal"><span class="pre">avx512knl-x16</span></tt> has been removed.</li>
<li>The <tt class="docutils literal"><span class="pre">--darwin-version-min</span></tt> option has been added to specify the minimum
deployment target version for macOS and iOS applications. This addresses a new
linker behavior introduced in Xcode 15.0, which issues a warning when no
version is provided.</li>
</ul>
<p>The behavior of user programs when no supported ISA is detected in the
auto-dispatch code has changed. Instead of raising the <tt class="docutils literal">SIGABRT</tt> signal, the
system will now raise <tt class="docutils literal">SIGILL</tt>. This affects users who rely on <tt class="docutils literal">SIGABRT</tt> in
their signal handlers for error handling or recovery. Such users must update
their code to handle <tt class="docutils literal">SIGILL</tt> instead. This change improves predictability and
removes the dispatcher's reliance on the C standard library.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-25-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.25.0</h2>
<p>The ISPC language has been extended to support the <tt class="docutils literal"><span class="pre">__attribute__(())</span></tt> syntax
for variable and function declarations. The following attributes are now
supported: <tt class="docutils literal">noescape</tt>, <tt class="docutils literal">address_space(N)</tt>, <tt class="docutils literal">external_only</tt>, and
<tt class="docutils literal">unmangled</tt>. The macro <tt class="docutils literal">ISPC_ATTRIBUTE_SUPPORTED</tt> is defined if the ISPC
compiler supports attribute syntax. Please refer to the <a class="reference internal" href="#attributes">Attributes</a> section
for more details and the full list of supported attributes.</p>
<p>This release introduces support for the <tt class="docutils literal"><span class="pre">-ffunction-sections</span></tt> command-line
flag, which generates each function in a separate section. This flag is useful
for reducing the size of the final executable by removing unused functions.
Please refer to the <a class="reference internal" href="#basic-command-line-options">Basic Command-line Options</a> section for more details.</p>
<p>In some cases, such as shared libraries, the <tt class="docutils literal"><span class="pre">-ffunction-sections</span></tt> flag alone
may not be sufficient to remove unused ISPC copies of exported functions. To
address this, you can use the <tt class="docutils literal">external_only</tt> function attribute. This
attribute can only be applied to exported functions and instructs the compiler
to remove the ISPC version of the function. For more information, please refer
to the <a class="reference internal" href="#attributes">Attributes</a> and <a class="reference internal" href="#functions-and-function-calls">Functions and Function Calls</a> sections.</p>
<p>Template support for short vectors and array declarations has been extended.
You can now use both type and non-type parameters to specify the type and
dimensions of these types.</p>
<p>For ARM targets, IEEE 754-compliant instructions (<tt class="docutils literal">fminnm</tt> and <tt class="docutils literal">vminnm</tt>) are
now generated for min/max operations, replacing the previous use of <tt class="docutils literal">fmin</tt> and
<tt class="docutils literal">vmin</tt>.</p>
<p>The <tt class="docutils literal"><span class="pre">avx512knl-x16</span></tt>, <tt class="docutils literal"><span class="pre">gen9-x8</span></tt>, and <tt class="docutils literal"><span class="pre">gen9-x16</span></tt> targets are deprecated and
will be removed in future releases.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-24-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.24.0</h2>
<p>This release extends the standard library with new functions performing dot
product operations. These functions utilize specific hardware instructions from
AVX-VNNI and AVX512-VNNI. The ISPC targets that support native VNNI
instructions are <tt class="docutils literal"><span class="pre">avx2vnni-i32x*</span></tt>, <tt class="docutils literal"><span class="pre">avx512icl-*</span></tt> and <tt class="docutils literal"><span class="pre">avx512spr-*</span></tt>. The
first two targets (<tt class="docutils literal"><span class="pre">avx2vnni-*</span></tt> and <tt class="docutils literal"><span class="pre">avx512icl-*</span></tt>) were introduced in this
release. Please refer to <a class="reference internal" href="#dot-product">Dot product</a> for more details.</p>
<p>Now, uniform integers and enums can be used as non-type template parameters.
Please refer to <a class="reference internal" href="#function-templates">Function Templates</a> for more details.</p>
<p>The release contains the following changes that may affect compatibility with
older versions:</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">--pic</span></tt> command line flag now corresponds to the <tt class="docutils literal"><span class="pre">-fpic</span></tt> flag of Clang
and GCC, whereas the newly introduced <tt class="docutils literal"><span class="pre">--PIC</span></tt> corresponds to <tt class="docutils literal"><span class="pre">-fPIC</span></tt>.
The previous behavior of <tt class="docutils literal"><span class="pre">--pic</span></tt> flag corresponded to <tt class="docutils literal"><span class="pre">-fPIC</span></tt> flag. In
some cases, to preserve previous behavior, users may need to switch to
<tt class="docutils literal"><span class="pre">--PIC</span></tt>.</li>
<li>Newly introduced macro definitions for numeric limits can cause conflicts
with user-defined macros with same names. When this happens, ISPC emits
warnings about macro redefinition. Please, refer to <a class="reference internal" href="#the-preprocessor">The Preprocessor</a> for
the full list of macro definitions.</li>
<li>The implementation of <tt class="docutils literal">round</tt> standard library function was aligned across
all targets. It may potentially affect the results of the code that uses this
function for the following targets: <tt class="docutils literal"><span class="pre">avx2-i16x16</span></tt>, <tt class="docutils literal"><span class="pre">avx2-i8x32</span></tt> and all
AVX-512 targets. Please, refer to <a class="reference internal" href="#basic-math-functions">Basic Math Functions</a> for more details.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-23-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.23.0</h2>
<p>This release contains the following changes that may affect compatibility with
older versions:</p>
<ul class="simple">
<li><cite>true</cite> <cite>bool</cite> values in storage were changed from <cite>-1</cite> to <cite>1</cite> to match C/C++ ABI.
Previously, ISPC treated <cite>bool</cite> values similarly to C/C++ in terms of size, but
incorrectly interpreted their actual values. This meant that <cite>true</cite> in ISPC
might not have translated correctly to true in C/C++. This issue was introduced
in version 1.13.0. Starting now, ISPC correctly stores and interprets <cite>true</cite>
values in a way that aligns with C/C++ expectations.</li>
</ul>
<p>A couple of improvements have been made to variables initialization:</p>
<ul class="simple">
<li>Variables with const qualifiers can be initialized using the values of
previously initialized const variables including arithmetic operations above
them. It now works also with varying types.</li>
<li>Enumeration type values can be used as constants.</li>
</ul>
<p>The result of selection operator can now be used as lvalue if it has suitable
type.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-22-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.22.0</h2>
<p>Template operators with explicit specializations and instantiations were introduced to
the language. The usage of different function specifiers with templates were fixed and
aligned, please refer to <a class="reference internal" href="#function-templates">Function Templates</a> section for more details.</p>
<p>Now, command-line switch <cite>--dwarf-version=<n></cite> forces DWARF format debug info generation
on Windows. It allows to debug ISPC code linked with MinGW generated code.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-21-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.21.0</h2>
<p>Now, in case of signed integer overflow, <cite>ispc</cite> will assume undefined behavior similar to
C and C++. This change may cause compatibility issues. You can manage this behavior by
using the <cite>--[no-]wrap-signed-int</cite> compiler switch. The default behavior (before version
1.21.0) can be preserved by using <cite>--wrap-signed-int</cite>, which maintains defined wraparound
behavior for signed integers, though it may limit some compiler optimizations.</p>
<p>Template function specializations with explicit template arguments were introduced to the
language, please refer to <a class="reference internal" href="#function-templates">Function Templates</a> section for more details.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-20-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.20.0</h2>
<p>New version of <cite>sse4</cite> targets were added, now you can specify either <cite>sse4.1</cite>
or <cite>sse4.2</cite>, for example <cite>sse4.2-i32x4</cite>. The changes are fully backward
compatible, meaning that <cite>sse4</cite> versions are still accepted and aliased to
<cite>sse4.2</cite>. Multi-target compilation accepts only one of <cite>sse4</cite>/<cite>sse4.1</cite>/<cite>sse4.2</cite>
targets. All of these targets will produce an object file with <cite>sse4</cite> suffix in
multi-target compilation.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-19-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.19.0</h2>
<p>New targets were added:</p>
<ul class="simple">
<li>avx512spr-x4, avx512spr-x8, avx512spr-x16, avx512spr-x32, avx512spr-x64 for
4th generation Intel® Xeon® Scalable (codename Sapphire Rapids) CPUs. A macro
<tt class="docutils literal">ISPC_TARGET_AVX512SPR</tt> was added.</li>
<li>xehpc-x16 and xehpc-x32 for Intel® Data Center GPU Max (codename Ponte Vecchio).</li>
</ul>
<p>Function templates were introduced to the language, please refer to the <a class="reference internal" href="#function-templates">Function
Templates</a> section for more details. Two new keywords were introduced: <tt class="docutils literal">template</tt>
and <tt class="docutils literal">typename</tt>.</p>
<p><tt class="docutils literal">ISPC_FP16_SUPPORTED</tt> macro was introduced for the targets supporting FP16.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-18-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.18.0</h2>
<p>AVX-512 targets were renamed to drop "base type" (or "mask size"), old naming is accepted for
compatibility. New names are avx512skx-x4, avx512skx-x8, avx512skx-x16,
avx512skx-x32, avx512skx-x64, and avx512knl-x16.</p>
<p>Standard library gained full support for <tt class="docutils literal">float16</tt> type. Note that it is
fully supported only on the targets with native hardware support.
On the other targets emulation is still not guaranteed, but may work in some cases.</p>
<p>The compiler gained support for <tt class="docutils literal"><span class="pre">-E</span></tt> switch for running preprocessor only,
which is similar to the switch of C/C++ compilers. Also, as a result of bug fix,
in case of preprocessor error, the compiler will crash now. It used not to crash and
produced some output (sometimes correct!). As it was a convenient feature for some
users running experiments in isolated environment (like ignoring missing includes
when compiling on <a class="reference external" href="https://godbolt.org/">Compiler Explorer</a>), the <tt class="docutils literal"><span class="pre">--ignore-preprocessor-errors</span></tt> switch
was added to preserve this behavior.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-17-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.17.0</h2>
<p>The release introduces new data type <tt class="docutils literal">float16</tt> and floating point literals
with <tt class="docutils literal">f16</tt> suffix.</p>
<p>For the sake of unification with C/C++, capital letter X may be used in
hexadecimal prefix (<tt class="docutils literal">0X</tt>) and capital letter P as a separator for exponent in
hexadecimal floating point. For example: <tt class="docutils literal">0X1P16</tt>.</p>
<p>The naming of Xe targets, architectures, device names has changed.</p>
<p>The standard library got new <tt class="docutils literal"><span class="pre">prefetchw_{l1,l2,l3}()</span></tt> intrinsics for
prefetching in anticipation of a write.</p>
<p>The algorithms used for implementation of <tt class="docutils literal">rsqrt(double)</tt> and <tt class="docutils literal">rcp(double)</tt>
standard library functions have changed on AVX-512 and may affect the existing
code.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-16-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.16.0</h2>
<p>The release has several new functions in the standard library that may
affect compatibility:</p>
<ul class="simple">
<li><tt class="docutils literal">alloca()</tt> - refer to <a class="reference internal" href="#stack-memory-allocation">Stack Memory Allocation</a> for more details.</li>
<li><tt class="docutils literal">assume()</tt> - refer to <a class="reference internal" href="#compiler-optimization-hints">Compiler Optimization Hints</a> for more details.</li>
<li><tt class="docutils literal">trunc()</tt> - refer to <a class="reference internal" href="#basic-math-functions">Basic Math Functions</a> for more details.</li>
</ul>
<p>The language got experimental feature for calling LLVM intrinsics. This
should not affect compatibility with existing programs.
See <a class="reference internal" href="#llvm-intrinsic-functions">LLVM Intrinsic Functions</a> for more details.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-15-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.15.0</h2>
<p>The release has several new language features, which do not affect compatibility.
Namely, packed_[load|store]_active() stdlib functions for 64 bit types, and loop
unroll pragmas: "#pragma unroll" and "#pragma nounroll".</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-14-1">
<h2>Updating ISPC Programs For Changes In ISPC 1.14.1</h2>
<p>The release doesn't contain language changes, which may affect compatibility with
older versions.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-14-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.14.0</h2>
<p>This release contains the following changes that may affect compatibility with
older versions:</p>
<ul class="simple">
<li>"generic" targets were removed. Please use native targets instead.</li>
</ul>
<p>New i8 and i16 targets were introduced: avx2-i8x32, avx2-i16x16, avx512skx-i8x64,
and avx512skx-i16x32.</p>
<p>Windows x86_64 target now supports <tt class="docutils literal">__vectorcall</tt> calling convention.
It's off by default, can be enabled by <tt class="docutils literal"><span class="pre">--vectorcall</span></tt> command line switch.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-13-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.13.0</h2>
<p>This release contains the following changes that may affect compatibility with
older versions:</p>
<ul class="simple">
<li>Representation of <tt class="docutils literal">bool</tt> type in storage was changed from target-specific to
one byte per boolean value. So size of <tt class="docutils literal">varying bool</tt> is target width (in
bytes), and size of <tt class="docutils literal">uniform bool</tt> is one. This definition is compatible
with C/C++, hence improves interoperability.</li>
<li>type aliases for unsigned types were added: <tt class="docutils literal">uint8</tt>, <tt class="docutils literal">uint16</tt>, <tt class="docutils literal">uint32</tt>,
<tt class="docutils literal">uint64</tt>, and <tt class="docutils literal">uint</tt>. To detect if these types are supported you can
check if ISPC_UINT_IS_DEFINED macro is defined, this is handy for writing code
which works with older versions of <tt class="docutils literal">ispc</tt>.</li>
<li><tt class="docutils literal">extract()</tt>/<tt class="docutils literal">insert()</tt> for boolean arguments, and <tt class="docutils literal">abs()</tt> for all integer and
FP types were added to standard library.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-12-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.12.0</h2>
<p>This release contains the following changes that may affect compatibility with
older versions:</p>
<ul class="simple">
<li><tt class="docutils literal">noinline</tt> keyword was added.</li>
<li>Standard library functions <tt class="docutils literal">rsqrt_fast()</tt> and <tt class="docutils literal">rcp_fast()</tt> were added.</li>
<li>AVX1.1 (IvyBridge) targets and generic KNC and KNL targets were removed.
Note that KNL is still supported through avx512knl-i32x16.</li>
</ul>
<p>The release also introduces static initialization for varying variables, which
should not affect compatibility.</p>
<p>This release introduces experimental cross OS compilation support and ARM/AARCH64
support. It also contains a new 128-bit AVX2 target (avx2-i32x4) and a CPU
definition for Ice Lake client (--device=icl).</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-11-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.11.0</h2>
<p>This release redefined the -O1 compiler option to optimize for size, so it may require
adjusting your build system accordingly.</p>
<p>Starting with version 1.11.0, auto-generated headers use <tt class="docutils literal">#pragma once</tt>. In the unlikely
case that your C/C++ compiler does not support that, please use the <tt class="docutils literal"><span class="pre">--no-pragma-once</span></tt>
<tt class="docutils literal">ispc</tt> switch.</p>
<p>This release also introduces a new AVX-512 target avx512skx-i32x8. It produces code,
which doesn't use ZMM registers.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-10-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.10.0</h2>
<p>The release has several new language features, which do not affect compatibility.
Namely, new streaming stores, aos_to_soa/soa_to_aos intrinsics for 64 bit types,
and a "#pragma ignore".</p>
<p>One change that may potentially affect compatibility is the changed size of short vector
types. If you use short vector types for data passed between C/C++ and ISPC, you
may want to pay attention to it.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-9-2">
<h2>Updating ISPC Programs For Changes In ISPC 1.9.2</h2>
<p>The release doesn't contain language changes, which may affect compatibility with
older versions.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-9-1">
<h2>Updating ISPC Programs For Changes In ISPC 1.9.1</h2>
<p>The release doesn't contain language changes, which may affect compatibility with
older versions. It introduces new AVX-512 target: avx512skx-i32x16.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-9-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.9.0</h2>
<p>The release doesn't contain language changes, which may affect compatibility with
older versions. It introduces new AVX-512 target: avx512knl-i32x16.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-8-2">
<h2>Updating ISPC Programs For Changes In ISPC 1.8.2</h2>
<p>The release doesn't contain language changes, which may affect compatibility with
older versions. Though you may want to be aware of the following:</p>
<ul class="simple">
<li>Mangling of uniform types was changed to not include varying width, so now you
may use uniform structures and pointers to uniform types as return types in
export functions in multi-target compilation.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-7-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.7.0</h2>
<p>This release contains several changes that may affect compatibility with
older versions:</p>
<ul class="simple">
<li>The algorithm for selecting overloaded functions was extended to cover more
types of overloading, and handling of reference types was fixed. At the same
time the old scheme, which blindly used the function with "the best score"
summed for all arguments, was switched to the C++ approach, which requires
"the best score" for each argument. If the best function doesn't exist, a
warning is issued in this version. It will be turned into an error in the
next version. A simple example: Suppose we have two functions: max(int, int)
and max(unsigned int, unsigned int). The new rules lead to an error when
calling max(int, unsigned int), as the best choice is ambiguous.</li>
<li>Implicit cast of pointer to const type to void* was disallowed. Use explicit
cast if needed.</li>
<li>A bug which prevented "const" qualifiers from appearing in emitted .h files
was fixed. Consequently, "const" qualifiers now properly appearing in emitted
.h files may cause compile errors in pre-existing codes.</li>
<li>get_ProgramCount() was moved from stdlib to examples/util/util.isph file. You
need to include this file to be able to use this function.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-6-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.6.0</h2>
<p>This release adds support for <a class="reference internal" href="#operators-overloading">Operators Overloading</a>, so a word <tt class="docutils literal">operator</tt>
becomes a keyword and it potentially creates a conflict with existing user
function. Also a new library function packed_store_active2() was introduced,
which also may create a conflict with existing user functions.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-5-0">
<h2>Updating ISPC Programs For Changes In ISPC 1.5.0</h2>
<p>This release adds support for double precision floating point constants.
Double precision floating point constants are floating point number with
<tt class="docutils literal">d</tt> suffix and optional exponent part. Here are some examples: 3.14d,
31.4d-1, 1.d, 1.0d, 1d-2. Note that floating point number without suffix is
treated as single precision constant.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-3">
<h2>Updating ISPC Programs For Changes In ISPC 1.3</h2>
<p>This release adds a number of new iteration constructs, which in turn use
new reserved words: <tt class="docutils literal">unmasked</tt>, <tt class="docutils literal">foreach_unique</tt>, <tt class="docutils literal">foreach_active</tt>,
and <tt class="docutils literal">in</tt>. Any program that happens to have a variable or function with
one of these names must be modified to rename that symbol.</p>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-2">
<h2>Updating ISPC Programs For Changes In ISPC 1.2</h2>
<p>The following changes were made to the language syntax and semantics for
the <tt class="docutils literal">ispc</tt> 1.2 release:</p>
<ul class="simple">
<li>Syntax for the "launch" keyword has been cleaned up; it's now no longer
necessary to bracket the launched function call with angle brackets. (In
other words, now use <tt class="docutils literal">launch <span class="pre">foo();</span></tt>, rather than <tt class="docutils literal">launch < foo() >;</tt>.)</li>
<li>When using pointers, the pointed-to data type is now "uniform" by
default. Use the varying keyword to specify varying pointed-to types
when needed. (i.e. <tt class="docutils literal">float *ptr</tt> is a varying pointer to uniform float
data, whereas previously it was a varying pointer to varying float
values.) Use <tt class="docutils literal">varying float *</tt> to specify a varying pointer to varying
float data, and so forth.</li>
<li>The details of "uniform" and "varying" and how they interact with struct
types have been cleaned up. Now, when a struct type is declared, if the
struct elements don't have explicit "uniform" or "varying" qualifiers,
they are said to have "unbound" variability. When a struct type is
instantiated, any unbound variability elements inherit the variability of
the parent struct type. See <a class="reference internal" href="#struct-types">Struct Types</a> for more details.</li>
<li><tt class="docutils literal">ispc</tt> has a new language feature that makes it much easier to use the
efficient "(array of) structure of arrays" (AoSoA, or SoA) memory layout
of data. A new <tt class="docutils literal">soa<n></tt> qualifier can be applied to structure types to
specify an n-wide SoA version of the corresponding type. Array indexing
and pointer operations with arrays SoA types automatically handles the
two-stage indexing calculation to access the data. See <a class="reference internal" href="#structure-of-array-types">Structure of
Array Types</a> for more details.</li>
</ul>
</div>
<div class="section" id="updating-ispc-programs-for-changes-in-ispc-1-1">
<h2>Updating ISPC Programs For Changes In ISPC 1.1</h2>
<p>The major changes introduced in the 1.1 release of <tt class="docutils literal">ispc</tt> are first-class
support for pointers in the language and new parallel loop constructs.
Adding this functionality required a number of syntactic changes to the
language. These changes should generally lead to straightforward minor
modifications of existing <tt class="docutils literal">ispc</tt> programs.</p>
<p>These are the relevant changes to the language:</p>
<ul class="simple">
<li>The syntax for reference types has been changed to match C++'s syntax for
references and the <tt class="docutils literal">reference</tt> keyword has been removed. (A diagnostic
message is issued if <tt class="docutils literal">reference</tt> is used.)<ul>
<li>Declarations like <tt class="docutils literal">reference float foo</tt> should be changed to <tt class="docutils literal">float &foo</tt>.</li>
<li>Any array parameters in function declaration with a <tt class="docutils literal">reference</tt>
qualifier should just have <tt class="docutils literal">reference</tt> removed: <tt class="docutils literal">void foo(reference
float <span class="pre">bar[])</span></tt> can just be <tt class="docutils literal">void foo(float <span class="pre">bar[])</span></tt>.</li>
</ul>
</li>
<li>It is now a compile-time error to assign an entire array to another
array.</li>
<li>A number of standard library routines have been updated to take
pointer-typed parameters, rather than references or arrays an index
offsets, as appropriate. For example, the <tt class="docutils literal">atomic_add_global()</tt>
function previously took a reference to the variable to be updated
atomically but now takes a pointer. In a similar fashion,
<tt class="docutils literal">packed_store_active()</tt> takes a pointer to a <tt class="docutils literal">uniform unsigned int</tt>
as its first parameter rather than taking a <tt class="docutils literal">uniform unsigned int[]</tt> as
its first parameter and a <tt class="docutils literal">uniform int</tt> offset as its second parameter.</li>
<li>It is no longer legal to pass a varying lvalue to a function that takes a
reference parameter; references can only be to uniform lvalue types. In
this case, the function should be rewritten to take a varying pointer
parameter.</li>
<li>There are new iteration constructs for looping over computation domains,
<tt class="docutils literal">foreach</tt> and <tt class="docutils literal">foreach_tiled</tt>. In addition to being syntactically
cleaner than regular <tt class="docutils literal">for</tt> loops, these can provide performance
benefits in many cases when iterating over data and mapping it to program
instances. See the Section <a class="reference internal" href="#parallel-iteration-statements-foreach-and-foreach-tiled">Parallel Iteration Statements: "foreach" and
"foreach_tiled"</a> for more information about these.</li>
</ul>
</div>
</div>
<div class="section" id="getting-started-with-ispc">
<h1>Getting Started with ISPC</h1>
<div class="section" id="installing-ispc">
<h2>Installing ISPC</h2>