================
@@ -4105,17 +4102,42 @@ LValue ScalarExprEmitter::EmitCompoundAssignLValue(
// the loaded integer to double, performing FP arithmetics, and truncation
// back as a single atomic operation. Integer promotion is still
// semantically safe.
- bool CanEmitAtomicRMW =
- !AtomicValueTy->isBooleanType() && AtomicValueTy->isIntegerType() &&
- ResultTy->isIntegerType() &&
- !(AtomicValueTy->isUnsignedIntegerType() &&
- CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) &&
- CGF.getLangOpts().getSignedOverflowBehavior() !=
- LangOptions::SOB_Trapping;
+ bool CanEmitAtomicRMW;
+ if (AtomicValueTy->isFloatingType()) {
+ llvm::Type *IRTy = CGF.ConvertType(AtomicValueTy);
+ uint64_t StoreBits =
CGF.CGM.getDataLayout().getTypeStoreSizeInBits(IRTy);
+ // Floating atomicrmw operations cannot model constrained FP semantics.
+ CanEmitAtomicRMW =
+ !OpInfo.FPFeatures.isFPConstrained() &&
+ CGF.getContext().hasSameUnqualifiedType(AtomicValueTy, ResultTy) &&
+ llvm::isPowerOf2_64(StoreBits);
----------------
Lukacma wrote:
This is coming from [LangRef](https://llvm.org/docs/LangRef.html#i-atomicrmw):
> For all of these operations, the type of <value> must be a type whose bit
> width is a power of two greater than or equal to eight.
For integer the check isn't necessary as nobody uses non power of 2 integer
types, but for floating point x86 uses x86_fp80 type, which cannot be used with
atomicrmw node, so we cannot do the optimization then.
https://github.com/llvm/llvm-project/pull/216033
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