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[LLVM-C] Allow LLVM{Get,Set}Volatile to work on memory intrinsics #162810

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[LLVM-C] Allow LLVM{Get,Set}Volatile to work on memory intrinsics #162810

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1 change: 1 addition & 0 deletions llvm/docs/ReleaseNotes.md
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Original file line number Diff line number Diff line change
Expand Up @@ -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` and `LLVMSetVolatile` to work on memory intrinsics like `memset`, `memcpy`, and `memmove`.

Changes to the CodeGen infrastructure
-------------------------------------
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4 changes: 4 additions & 0 deletions llvm/lib/IR/Core.cpp
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Expand Up @@ -4106,6 +4106,8 @@ LLVMBool LLVMGetVolatile(LLVMValueRef MemAccessInst) {
return SI->isVolatile();
if (AtomicRMWInst *AI = dyn_cast<AtomicRMWInst>(P))
return AI->isVolatile();
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(P))
return MI->isVolatile();
return cast<AtomicCmpXchgInst>(P)->isVolatile();
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We could replace this whole function with cast<Instruction>(P)->isVolatile(). This would just return false for instructions that don't support volatile.

}

Expand All @@ -4117,6 +4119,8 @@ void LLVMSetVolatile(LLVMValueRef MemAccessInst, LLVMBool isVolatile) {
return SI->setVolatile(isVolatile);
if (AtomicRMWInst *AI = dyn_cast<AtomicRMWInst>(P))
return AI->setVolatile(isVolatile);
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(P))
return MI->setVolatile(ConstantInt::getBool(P->getContext(), isVolatile));
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After thinking about this a bit more, I'm not sure we should do this. I am planning to change the volatile representation for memory intrinsics from an argument to an operand bundle. This means that it will no longer be possible to make the intrinsic volatile in-place, it requires creating a new one. So there is a high risk that this support is going to be very short-lived.

return cast<AtomicCmpXchgInst>(P)->setVolatile(isVolatile);
}

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105 changes: 105 additions & 0 deletions llvm/unittests/IR/InstructionsTest.cpp
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Expand Up @@ -1933,5 +1933,110 @@ TEST(InstructionsTest, StripAndAccumulateConstantOffset) {
EXPECT_TRUE(Offset.isZero());
}

TEST(InstructionsTest, LLVMGetSetVolatile) {
LLVMContext Ctx;
Module M("M", Ctx);
FunctionType *FT = FunctionType::get(Type::getVoidTy(Ctx), {}, false);
Function *F = Function::Create(FT, Function::ExternalLinkage, "F", M);
BasicBlock *BB = BasicBlock::Create(Ctx, "entry", F);
IRBuilder<> B(BB);

Type *Int32Ty = Type::getInt32Ty(Ctx);
Value *Val = B.getInt32(1);
Value *Ptr = B.CreateAlloca(Int32Ty);

// LoadInst
{
LoadInst *Load = B.CreateLoad(Int32Ty, Ptr, "");

EXPECT_FALSE(LLVMGetVolatile(wrap(Load)));
LLVMSetVolatile(wrap(Load), true);
EXPECT_TRUE(LLVMGetVolatile(wrap(Load)));
LLVMSetVolatile(wrap(Load), false);
EXPECT_FALSE(LLVMGetVolatile(wrap(Load)));
}

// StoreInst
{
StoreInst *Store = B.CreateStore(Val, Ptr);

EXPECT_FALSE(LLVMGetVolatile(wrap(Store)));
LLVMSetVolatile(wrap(Store), true);
EXPECT_TRUE(LLVMGetVolatile(wrap(Store)));
LLVMSetVolatile(wrap(Store), false);
EXPECT_FALSE(LLVMGetVolatile(wrap(Store)));
}

// AtomicRMWInst
{
AtomicRMWInst *RMW = B.CreateAtomicRMW(
AtomicRMWInst::Add, Ptr, Val, MaybeAlign(), AtomicOrdering::Monotonic);

EXPECT_FALSE(LLVMGetVolatile(wrap(RMW)));
LLVMSetVolatile(wrap(RMW), true);
EXPECT_TRUE(LLVMGetVolatile(wrap(RMW)));
LLVMSetVolatile(wrap(RMW), false);
EXPECT_FALSE(LLVMGetVolatile(wrap(RMW)));
}

// MemCpy
{
CallInst *MemCpy = B.CreateMemCpy(Ptr, MaybeAlign(), Ptr, MaybeAlign(), 4);

EXPECT_FALSE(LLVMGetVolatile(wrap(MemCpy)));
LLVMSetVolatile(wrap(MemCpy), true);
EXPECT_TRUE(LLVMGetVolatile(wrap(MemCpy)));
LLVMSetVolatile(wrap(MemCpy), false);
EXPECT_FALSE(LLVMGetVolatile(wrap(MemCpy)));
}

// MemMove
{
CallInst *MemMove =
B.CreateMemMove(Ptr, MaybeAlign(), Ptr, MaybeAlign(), 4);

EXPECT_FALSE(LLVMGetVolatile(wrap(MemMove)));
LLVMSetVolatile(wrap(MemMove), true);
EXPECT_TRUE(LLVMGetVolatile(wrap(MemMove)));
LLVMSetVolatile(wrap(MemMove), false);
EXPECT_FALSE(LLVMGetVolatile(wrap(MemMove)));
}

// MemSet
{
CallInst *MemSet = B.CreateMemSet(Ptr, B.getInt8(0), 1, Align(1));

EXPECT_FALSE(LLVMGetVolatile(wrap(MemSet)));
LLVMSetVolatile(wrap(MemSet), true);
EXPECT_TRUE(LLVMGetVolatile(wrap(MemSet)));
LLVMSetVolatile(wrap(MemSet), false);
EXPECT_FALSE(LLVMGetVolatile(wrap(MemSet)));
}

// MemSetInline
{
CallInst *MemSetInline =
B.CreateMemSetInline(Ptr, Align(1), B.getInt8(0), Val);

EXPECT_FALSE(LLVMGetVolatile(wrap(MemSetInline)));
LLVMSetVolatile(wrap(MemSetInline), true);
EXPECT_TRUE(LLVMGetVolatile(wrap(MemSetInline)));
LLVMSetVolatile(wrap(MemSetInline), false);
EXPECT_FALSE(LLVMGetVolatile(wrap(MemSetInline)));
}

// MemCpyInline
{
CallInst *MemCpyInline =
B.CreateMemCpyInline(Ptr, MaybeAlign(), Val, MaybeAlign(), Val);

EXPECT_FALSE(LLVMGetVolatile(wrap(MemCpyInline)));
LLVMSetVolatile(wrap(MemCpyInline), true);
EXPECT_TRUE(LLVMGetVolatile(wrap(MemCpyInline)));
LLVMSetVolatile(wrap(MemCpyInline), false);
EXPECT_FALSE(LLVMGetVolatile(wrap(MemCpyInline)));
}
}

} // end anonymous namespace
} // end namespace llvm