[Feature] We should be able to walk through the operands of a call wi…

src/values/basic_value_use.rs

@@ -4,7 +4,7 @@ use llvm_sys::prelude::LLVMUseRef;
 use std::marker::PhantomData;
 
 use crate::basic_block::BasicBlock;
-use crate::values::{AnyValueEnum, BasicValueEnum};
+use crate::values::{AnyValueEnum, BasicValueEnum, MetadataValue};
 
 /// Either [BasicValueEnum] or [BasicBlock].
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -13,6 +13,8 @@ pub enum Operand<'ctx> {
     Value(BasicValueEnum<'ctx>),
     /// Represents a [BasicBlock].
     Block(BasicBlock<'ctx>),
+    /// Represents a [MetadataValue].
+    Metadata(MetadataValue<'ctx>),
 }
 
 impl<'ctx> Operand<'ctx> {

src/values/enums.rs

@@ -118,7 +118,7 @@ impl<'ctx> AnyValueEnum<'ctx> {
                 AnyValueEnum::InstructionValue(InstructionValue::new(value))
             },
             LLVMTypeKind::LLVMMetadataTypeKind => panic!("Metadata values are not supported as AnyValue's."),
-            _ => panic!("The given type is not supported."),
+            other => panic!("The given type is not supported: {:?}", other),
         }
     }
 
@@ -292,7 +292,7 @@ impl<'ctx> BasicValueEnum<'ctx> {
             LLVMTypeKind::LLVMScalableVectorTypeKind => {
                 BasicValueEnum::ScalableVectorValue(ScalableVectorValue::new(value))
             },
-            _ => unreachable!("The given type is not a basic type."),
+            other => panic!("The given type is not a basic type: {:?}", other),
         }
     }
 

src/values/instruction_value.rs

@@ -3,17 +3,17 @@ use llvm_sys::core::LLVMGetGEPSourceElementType;
 use llvm_sys::core::{
     LLVMGetAlignment, LLVMGetAllocatedType, LLVMGetFCmpPredicate, LLVMGetICmpPredicate, LLVMGetIndices,
     LLVMGetInstructionOpcode, LLVMGetInstructionParent, LLVMGetMetadata, LLVMGetNextInstruction, LLVMGetNumIndices,
-    LLVMGetNumOperands, LLVMGetOperand, LLVMGetOperandUse, LLVMGetPreviousInstruction, LLVMGetVolatile,
-    LLVMHasMetadata, LLVMInstructionClone, LLVMInstructionEraseFromParent, LLVMInstructionRemoveFromParent,
-    LLVMIsAAllocaInst, LLVMIsABasicBlock, LLVMIsAGetElementPtrInst, LLVMIsALoadInst, LLVMIsAStoreInst,
-    LLVMIsATerminatorInst, LLVMIsConditional, LLVMIsTailCall, LLVMSetAlignment, LLVMSetMetadata, LLVMSetOperand,
-    LLVMSetVolatile, LLVMValueAsBasicBlock,
+    LLVMGetNumOperands, LLVMGetOperand, LLVMGetOperandUse, LLVMGetPreviousInstruction, LLVMGetTypeKind,
+    LLVMGetVolatile, LLVMHasMetadata, LLVMInstructionClone, LLVMInstructionEraseFromParent,
+    LLVMInstructionRemoveFromParent, LLVMIsAAllocaInst, LLVMIsABasicBlock, LLVMIsAGetElementPtrInst, LLVMIsALoadInst,
+    LLVMIsAStoreInst, LLVMIsATerminatorInst, LLVMIsAValueAsMetadata, LLVMIsConditional, LLVMIsTailCall,
+    LLVMSetAlignment, LLVMSetMetadata, LLVMSetOperand, LLVMSetVolatile, LLVMTypeOf, LLVMValueAsBasicBlock,
 };
 #[llvm_versions(10..)]
 use llvm_sys::core::{LLVMGetAtomicRMWBinOp, LLVMIsAAtomicCmpXchgInst, LLVMIsAAtomicRMWInst};
 use llvm_sys::core::{LLVMGetOrdering, LLVMSetOrdering};
 use llvm_sys::prelude::LLVMValueRef;
-use llvm_sys::LLVMOpcode;
+use llvm_sys::{LLVMOpcode, LLVMTypeKind};
 
 use std::{ffi::CStr, fmt, fmt::Display};
 
@@ -684,14 +684,21 @@ impl<'ctx> InstructionValue<'ctx> {
         }
 
         let is_basic_block = unsafe { !LLVMIsABasicBlock(operand).is_null() };
-
         if is_basic_block {
             let bb = unsafe { BasicBlock::new(LLVMValueAsBasicBlock(operand)) };
 
-            Some(Operand::Block(bb.expect("BasicBlock should always be valid")))
-        } else {
-            Some(Operand::Value(unsafe { BasicValueEnum::new(operand) }))
+            return Some(Operand::Block(bb.expect("BasicBlock should always be valid")));
+        }
+
+        if unsafe { LLVMGetTypeKind(LLVMTypeOf(operand)) == LLVMTypeKind::LLVMMetadataTypeKind } {
+            // We may be dealing with null metadata, which would break memory invariants.
+            if LLVMIsAValueAsMetadata(operand).is_null() {
+                return None;
+            }
+            return Some(Operand::Metadata(MetadataValue::new(operand)));
         }
+
+        Some(Operand::Value(unsafe { BasicValueEnum::new(operand) }))
     }
 
     /// Get an instruction value operand iterator.

tests/all/test_instruction_values.rs

@@ -1,11 +1,12 @@
 use inkwell::context::Context;
+use inkwell::debug_info::AsDIScope;
 #[cfg(not(feature = "typed-pointers"))]
 use inkwell::types::AnyType;
 use inkwell::types::{AnyTypeEnum, BasicType};
 use inkwell::values::{BasicValue, CallSiteValue, InstructionOpcode::*};
 #[llvm_versions(10..)]
 use inkwell::AtomicRMWBinOp;
-use inkwell::{AddressSpace, AtomicOrdering, FloatPredicate, IntPredicate};
+use inkwell::{debug_info, AddressSpace, AtomicOrdering, FloatPredicate, IntPredicate};
 
 #[test]
 #[ignore]
@@ -661,6 +662,62 @@ fn test_metadata_kinds() {
     ]);
 }
 
+#[test]
+fn test_metadata_as_operand() {
+    // clang can introduce instructions such as
+    //  call void @llvm.dbg.declare(metadata i32* %2, metadata !16, metadata !DIExpression()), !dbg !17
+    // we want to make sure that looking at the operands works.
+
+    let context = Context::create();
+    let module = context.create_module("testing");
+
+    let void_type = context.void_type();
+    let i32_type = context.i32_type();
+    let fn_type = void_type.fn_type(&[], false);
+    let function = module.add_function("fun", fn_type, None);
+    let block = context.append_basic_block(function, "block");
+
+    let (debug_info_builder, compile_unit) = module.create_debug_info_builder(
+        true,
+        debug_info::DWARFSourceLanguage::C,
+        "test.ll",
+        "/tmp",
+        "test",
+        false,
+        "",
+        0,
+        "split",
+        debug_info::DWARFEmissionKind::Full,
+        0,
+        false,
+        false,
+        "/",
+        "18.1",
+    );
+
+    let address_space = AddressSpace::default();
+    let debug_loc = debug_info_builder.create_debug_location(&context, 5, 32, compile_unit.as_debug_info_scope(), None);
+    #[allow(deprecated)]
+    let i32_ptr = i32_type.ptr_type(address_space).const_null();
+    let di_i32_type = debug_info_builder.create_basic_type("i32", 32, 0, 0).unwrap();
+    let var_info = debug_info_builder.create_auto_variable(
+        compile_unit.as_debug_info_scope(),
+        "var",
+        compile_unit.get_file(),
+        42,
+        di_i32_type.as_type(),
+        false,
+        0,
+        32,
+    );
+    let instruction = debug_info_builder.insert_declare_at_end(i32_ptr, Some(var_info), None, debug_loc, block);
+    assert_eq!(instruction.get_num_operands(), 4);
+    assert!(instruction.get_operand(0).is_some());
+    assert!(instruction.get_operand(1).is_none());
+    assert!(instruction.get_operand(2).is_none());
+    assert!(instruction.get_operand(3).is_some());
+}
+
 #[test]
 fn test_find_instruction_with_name() {
     use inkwell::context::Context;