[LLVM-C] Allow LLVMGetVolatile to work with any kind of Instruction

[AMS21]

Allow LLVMGetVolatile() to work with any kind of Instruction, rather than only memory instructions that accept a volatile flag. For instructions that can never be volatile, the function now return false instead of asserting. This matches the behavior of Instruction::isVolatile() in the C++ API.

[llvmbot]

@llvm/pr-subscribers-llvm-ir

Author: None (AMS21)

Changes

As mentioned here

---

Full diff: https://github.com/llvm/llvm-project/pull/163060.diff

3 Files Affected:

• (modified) llvm/docs/ReleaseNotes.md (+1)
• (modified) llvm/include/llvm-c/Core.h (+1-1)
• (modified) llvm/lib/IR/Core.cpp (+2-9)

diff --git a/llvm/docs/ReleaseNotes.md b/llvm/docs/ReleaseNotes.md
index 79d93d08b8398..30aeccd3ee5bc 100644
--- a/llvm/docs/ReleaseNotes.md
+++ b/llvm/docs/ReleaseNotes.md
@@ -147,6 +147,7 @@ Changes to the C API
 --------------------
 
 * Add `LLVMGetOrInsertFunction` to get or insert a function, replacing the combination of `LLVMGetNamedFunction` and `LLVMAddFunction`.
+* Allow `LLVMGetVolatile` to work with any kind of Instruction.
 
 Changes to the CodeGen infrastructure
 -------------------------------------
diff --git a/llvm/include/llvm-c/Core.h b/llvm/include/llvm-c/Core.h
index 3d22f85911e78..4e380d9bd5969 100644
--- a/llvm/include/llvm-c/Core.h
+++ b/llvm/include/llvm-c/Core.h
@@ -4757,7 +4757,7 @@ LLVM_C_ABI LLVMValueRef LLVMBuildGlobalString(LLVMBuilderRef B, const char *Str,
 LLVM_C_ABI LLVMValueRef LLVMBuildGlobalStringPtr(LLVMBuilderRef B,
                                                  const char *Str,
                                                  const char *Name);
-LLVM_C_ABI LLVMBool LLVMGetVolatile(LLVMValueRef MemoryAccessInst);
+LLVM_C_ABI LLVMBool LLVMGetVolatile(LLVMValueRef Inst);
 LLVM_C_ABI void LLVMSetVolatile(LLVMValueRef MemoryAccessInst,
                                 LLVMBool IsVolatile);
 LLVM_C_ABI LLVMBool LLVMGetWeak(LLVMValueRef CmpXchgInst);
diff --git a/llvm/lib/IR/Core.cpp b/llvm/lib/IR/Core.cpp
index 3f1cc1e4e6d0e..27d8294b01264 100644
--- a/llvm/lib/IR/Core.cpp
+++ b/llvm/lib/IR/Core.cpp
@@ -4098,15 +4098,8 @@ LLVMValueRef LLVMBuildGlobalStringPtr(LLVMBuilderRef B, const char *Str,
   return wrap(unwrap(B)->CreateGlobalString(Str, Name));
 }
 
-LLVMBool LLVMGetVolatile(LLVMValueRef MemAccessInst) {
-  Value *P = unwrap(MemAccessInst);
-  if (LoadInst *LI = dyn_cast<LoadInst>(P))
-    return LI->isVolatile();
-  if (StoreInst *SI = dyn_cast<StoreInst>(P))
-    return SI->isVolatile();
-  if (AtomicRMWInst *AI = dyn_cast<AtomicRMWInst>(P))
-    return AI->isVolatile();
-  return cast<AtomicCmpXchgInst>(P)->isVolatile();
+LLVMBool LLVMGetVolatile(LLVMValueRef Inst) {
+  return cast<Instruction>(unwrap(Inst))->isVolatile();
 }
 
 void LLVMSetVolatile(LLVMValueRef MemAccessInst, LLVMBool isVolatile) {

[nikic]

LGTM. Matches the C++ API in that isVolatile() works on any instruction, while setVolatile() is only available on specific ones.