================
@@ -833,24 +833,42 @@ void
HLSLExternalSemaSource::defineHLSLTypesWithForwardDeclarations() {
}
}
+// Shapes of the synthesized atomic overloads. The read-modify-write operations
+// can report the previous value through a trailing reference. Every argument
+// of compare-store is an input.
+enum class AtomicOverloadShape {
+ Binary, // (dest, value)
+ BinaryWithOriginal, // (dest, value, original_value)
+ CompareStore, // (dest, compare_value, value)
+};
+
// Build a single overload of an HLSL atomic intrinsic in the hlsl namespace.
// `dest` is an address-space-qualified reference; `original_value` (when
// present) is a plain reference. The synthesized FunctionDecl aliases the
// underlying clang builtin via BuiltinAliasAttr.
static void buildAtomicOverload(Sema &S, NamespaceDecl *NS, StringRef FuncName,
StringRef BuiltinName, QualType ElemTy,
- LangAS DestAS, bool ThreeArg) {
+ LangAS DestAS, AtomicOverloadShape Shape) {
ASTContext &AST = S.getASTContext();
QualType DestTy =
AST.getLValueReferenceType(AST.getAddrSpaceQualType(ElemTy, DestAS));
QualType OrigRefTy = AST.getLValueReferenceType(ElemTy);
- SmallVector<QualType, 3> ParamTypes;
- ParamTypes.push_back(DestTy);
- ParamTypes.push_back(ElemTy);
- if (ThreeArg)
+ SmallVector<QualType, 3> ParamTypes = {DestTy, ElemTy};
+ if (Shape == AtomicOverloadShape::BinaryWithOriginal)
ParamTypes.push_back(OrigRefTy);
+ else if (Shape == AtomicOverloadShape::CompareStore)
+ ParamTypes.push_back(ElemTy);
----------------
bob80905 wrote:
When checking against DXC, it looks like it automatically casts into uint. Your
DXC example is probably in range of 0 - uint max.
Do you get the same thing if you try RWStructedBuffer<uint> ?
If you gave DXC something larger than uintmax, then it should emit `undef`.
DXC converts the operands to uint, where 2147483648 and 4294967040 are both in
range, so it folds them to the bit patterns -2147483648 and -256. Clang
converts to the destination element type `int`, where the same literals are out
of range, so it warns and emits poison.
Give DXC a genuinely out-of-range value for uint, and it should emit undef, the
old-LLVM equivalent of poison.
I think we want to keep the current behavior because if the buffer is of type
int, then DXC emits undef, while clang emits -5.0f correctly as -5u.
https://github.com/llvm/llvm-project/pull/222164
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