From cce7e6a118d7a08bcb9185ba29b13207247f0092 Mon Sep 17 00:00:00 2001
From: Andrea Bocci <andrea.bocci@cern.ch>
Date: Sun, 11 Jan 2026 10:59:24 +0100
Subject: [PATCH 1/2] Do not use -Ofast

-Ofast implies -funsafe-math-optimizations, which affects the global FP state
for all programs: when used at link time, it may include libraries or startup
files that change the default FPU control word or other similar optimizations.
---
 xz-bootstrap.spec | 2 +-
 xz.spec           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xz-bootstrap.spec b/xz-bootstrap.spec
index 2f24e800132..16773fe46a9 100644
--- a/xz-bootstrap.spec
+++ b/xz-bootstrap.spec
@@ -5,7 +5,7 @@ Source0: http://tukaani.org/xz/xz-%{realversion}.tar.gz
 %setup -n xz-%{realversion}
 
 %build
-./configure CFLAGS='-fPIC -D_FILE_OFFSET_BITS=64 -Ofast' --prefix=%{i} --disable-static
+./configure CFLAGS='-fPIC -D_FILE_OFFSET_BITS=64 -O3' --prefix=%{i} --disable-static
 make %{makeprocesses}
 
 %install
diff --git a/xz.spec b/xz.spec
index 10a2494058f..2b1094aaf51 100644
--- a/xz.spec
+++ b/xz.spec
@@ -7,7 +7,7 @@ BuildRequires: autotools
 %setup -n %{n}-%{realversion}
 
 %build
-./configure CFLAGS='-fPIC -Ofast' --prefix=%{i} --disable-static --disable-nls --disable-rpath --disable-dependency-tracking --disable-doc
+./configure CFLAGS='-fPIC -O3' --prefix=%{i} --disable-static --disable-nls --disable-rpath --disable-dependency-tracking --disable-doc
 make %{makeprocesses}
 
 %install

From 70c5c865655c8cd8620ccefb3ebb09766a1bd73f Mon Sep 17 00:00:00 2001
From: Andrea Bocci <andrea.bocci@cern.ch>
Date: Sun, 11 Jan 2026 10:59:24 +0100
Subject: [PATCH 2/2] Do not use -Ofast
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

-Ofast implies -funsafe-math-optimizations, which affects the global FP state
for all programs: when used at link time, it may include libraries or startup
files that change the default FPU control word or other similar optimizations.

-Ofast enables (directly or indirectly):
  - ❌ -fallow-store-data-races
  - ✔ -fno-semantic-interposition
  - ✔ -fno-math-errno
  - ❌ -funsafe-math-optimizations
  - ❌ -ffinite-math-only
  - ✔ -fno-rounding-math (_default_)
  - ✔ -fno-signaling-nans (_default_)
  - ❔ -fcx-limited-range
  - ✔ -fexcess-precision=fast
  - ✔ -fno-signed-zeros
  - ✔ -fno-trapping-math
  - ✔ -fassociative-math
  - ❌ -freciprocal-math (disabled in cms-sw/cmsdist#8280)

We should not use -fallow-store-data-races, -ffinite-math-only.

We should not use -funsafe-math-optimizations at link time, as it affects the
global FP state. It's probably easier to replace it with the individual options
-fno-signed-zeros, -fno-trapping-math and -fassociative-math.

We may revisit -fcx-limited-range if we do use Complex arithmetics.

-freciprocal-math was already disabled explicitly, see cms-sw/cmsdist#8280.
---
 scram-tools.file/tools/gcc/ofast-flag.xml | 36 +++++++++++++++--------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/scram-tools.file/tools/gcc/ofast-flag.xml b/scram-tools.file/tools/gcc/ofast-flag.xml
index f32a962f353..9ada2fe263c 100644
--- a/scram-tools.file/tools/gcc/ofast-flag.xml
+++ b/scram-tools.file/tools/gcc/ofast-flag.xml
@@ -1,12 +1,24 @@
-  <tool name="ofast-flag" version="1.0" revision="1">
-    <flags CXXFLAGS="-Ofast -fno-reciprocal-math"/>
-    <ifarch match="ppc64le|amd64|x86_64">
-      <flags CXXFLAGS="-mrecip=none"/>
-    </ifarch>
-    <ifarchitecture name="slc6_">
-      <ifcompiler name="llvm">
-        <flags CXXFLAGS="-fno-builtin"/>
-      </ifcompiler>
-    </ifarchitecture>
-    <flags NO_RECURSIVE_EXPORT="1"/>
-  </tool>
+<tool name="ofast-flag" version="2.0" revision="1">
+  <!--
+  As of GCC version 13.3.0, `-Ofast` enables (directly or indirectly):
+    - `-fallow-store-data-races`
+    - `-fno-semantic-interposition`
+    - `-fno-math-errno`
+    - `-funsafe-math-optimizations`
+    - `-ffinite-math-only`
+    - `-fno-rounding-math` (enabled by default)
+    - `-fno-signaling-nans` (enabled by default)
+    - `-fcx-limited-range`
+    - `-fexcess-precision=fast`
+    - `-fno-signed-zeros`
+    - `-fno-trapping-math`
+    - `-fassociative-math`
+    - `-freciprocal-math` (disabled in cms-sw/cmsdist#8280)
+  We disable `-fallow-store-data-races`, `-funsafe-math-optimizations`, `-ffinite-math-only` and `-freciprocal-math` (see cms-sw/cmsdist#8280).
+  -->
+  <flags CXXFLAGS="-fno-semantic-interposition -fno-math-errno -fno-rounding-math -fno-signaling-nans -fexcess-precision=fast -fno-signed-zeros -fno-trapping-math -fassociative-math -fno-reciprocal-math"/>
+  <ifarch match="ppc64le|amd64|x86_64">
+    <flags CXXFLAGS="-mrecip=none"/>
+  </ifarch>
+  <flags NO_RECURSIVE_EXPORT="1"/>
+</tool>