[clang] [HLSL][SPIRV] Add vk::constant_id attribute. (PR #143544)
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Tue Jun 10 07:45:56 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-hlsl
Author: Steven Perron (s-perron)
<details>
<summary>Changes</summary>
The vk::constant_id attribute is used to indicate that a global const variable
represents a specialization constant in SPIR-V. This PR adds this
attribute to clang.
The documetation for the attribute is [here](https://github.com/microsoft/DirectXShaderCompiler/blob/main/docs/SPIR-V.rst#specialization-constants).
The strategy is to to modify the initializer to get the value of a
specialize constant for a builtin defined in the SPIR-V backend.
---
Patch is 39.25 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/143544.diff
16 Files Affected:
- (modified) clang/include/clang/Basic/Attr.td (+8)
- (modified) clang/include/clang/Basic/AttrDocs.td (+15)
- (modified) clang/include/clang/Basic/Builtins.td (+13)
- (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+12)
- (modified) clang/include/clang/Sema/SemaHLSL.h (+4-1)
- (modified) clang/lib/Basic/Attributes.cpp (+2-1)
- (modified) clang/lib/CodeGen/CGHLSLBuiltins.cpp (+72)
- (modified) clang/lib/CodeGen/CodeGenFunction.h (+11)
- (modified) clang/lib/Sema/SemaDecl.cpp (+14)
- (modified) clang/lib/Sema/SemaDeclAttr.cpp (+3)
- (modified) clang/lib/Sema/SemaHLSL.cpp (+119-1)
- (added) clang/test/AST/HLSL/vk.spec-constant.usage.hlsl (+130)
- (renamed) clang/test/CodeGenHLSL/vk-features/SpirvType.alignment.hlsl ()
- (renamed) clang/test/CodeGenHLSL/vk-features/SpirvType.hlsl ()
- (added) clang/test/CodeGenHLSL/vk-features/vk.spec-constant.hlsl (+210)
- (added) clang/test/SemaHLSL/vk.spec-constant.error.hlsl (+37)
``````````diff
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index f889e41c8699f..d3f39de6a3e85 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -4993,6 +4993,14 @@ def HLSLVkExtBuiltinInput : InheritableAttr {
let Documentation = [HLSLVkExtBuiltinInputDocs];
}
+def HLSLVkConstantId : InheritableAttr {
+ let Spellings = [CXX11<"vk", "constant_id">];
+ let Args = [IntArgument<"Id">];
+ let Subjects = SubjectList<[ExternalGlobalVar]>;
+ let LangOpts = [HLSL];
+ let Documentation = [VkConstantIdDocs];
+}
+
def RandomizeLayout : InheritableAttr {
let Spellings = [GCC<"randomize_layout">];
let Subjects = SubjectList<[Record]>;
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index ea3c43f38d9fe..b3eafb79c5d4a 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -8252,6 +8252,21 @@ and https://microsoft.github.io/hlsl-specs/proposals/0013-wave-size-range.html
}];
}
+def VkConstantIdDocs : Documentation {
+ let Category = DocCatFunction;
+ let Content = [{
+The ``vk::constant_id`` attribute specify the id for a SPIR-V specialization
+constant. The attribute applies to const global scalar variables. The variable must be initialized with a C++11 constexpr.
+In SPIR-V, the
+variable will be replaced with an `OpSpecConstant` with the given id.
+The syntax is:
+
+.. code-block:: text
+
+ ``[[vk::constant_id(<Id>)]] const T Name = <Init>``
+}];
+}
+
def RootSignatureDocs : Documentation {
let Category = DocCatFunction;
let Content = [{
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index 68cd3d790e78a..d65b3a5d2f447 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -5065,6 +5065,19 @@ def HLSLGroupMemoryBarrierWithGroupSync: LangBuiltin<"HLSL_LANG"> {
let Prototype = "void()";
}
+class HLSLScalarTemplate
+ : Template<["bool", "char", "short", "int", "long long int",
+ "unsigned short", "unsigned int", "unsigned long long int",
+ "__fp16", "float", "double"],
+ ["_bool", "_char", "_short", "_int", "_longlong", "_ushort",
+ "_uint", "_ulonglong", "_half", "_float", "_double"]>;
+
+def HLSLGetSpirvSpecConstant : LangBuiltin<"HLSL_LANG">, HLSLScalarTemplate {
+ let Spellings = ["__builtin_get_spirv_spec_constant"];
+ let Attributes = [NoThrow, Const, Pure];
+ let Prototype = "T(unsigned int, T)";
+}
+
// Builtins for XRay.
def XRayCustomEvent : Builtin {
let Spellings = ["__xray_customevent"];
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 1f283b776a02c..23a490225dd19 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -12919,6 +12919,18 @@ def err_spirv_enum_not_int : Error<
def err_spirv_enum_not_valid : Error<
"invalid value for %select{storage class}0 argument">;
+def err_specialization_const_lit_init
+ : Error<"variable with 'vk::constant_id' attribute cannot have an "
+ "initializer that is not a constexpr">;
+def err_specialization_const_missing_initializer
+ : Error<
+ "variable with 'vk::constant_id' attribute must have an initializer">;
+def err_specialization_const_missing_const
+ : Error<"variable with 'vk::constant_id' attribute must be const">;
+def err_specialization_const_is_not_int_or_float
+ : Error<"variable with 'vk::constant_id' attribute must be an enum, bool, "
+ "integer, or floating point value">;
+
// errors of expect.with.probability
def err_probability_not_constant_float : Error<
"probability argument to __builtin_expect_with_probability must be constant "
diff --git a/clang/include/clang/Sema/SemaHLSL.h b/clang/include/clang/Sema/SemaHLSL.h
index 66d09f49680be..099d9c35684e8 100644
--- a/clang/include/clang/Sema/SemaHLSL.h
+++ b/clang/include/clang/Sema/SemaHLSL.h
@@ -98,6 +98,8 @@ class SemaHLSL : public SemaBase {
HLSLWaveSizeAttr *mergeWaveSizeAttr(Decl *D, const AttributeCommonInfo &AL,
int Min, int Max, int Preferred,
int SpelledArgsCount);
+ HLSLVkConstantIdAttr *
+ mergeVkConstantIdAttr(Decl *D, const AttributeCommonInfo &AL, int Id);
HLSLShaderAttr *mergeShaderAttr(Decl *D, const AttributeCommonInfo &AL,
llvm::Triple::EnvironmentType ShaderType);
HLSLParamModifierAttr *
@@ -122,6 +124,7 @@ class SemaHLSL : public SemaBase {
void handleRootSignatureAttr(Decl *D, const ParsedAttr &AL);
void handleNumThreadsAttr(Decl *D, const ParsedAttr &AL);
void handleWaveSizeAttr(Decl *D, const ParsedAttr &AL);
+ void handleVkConstantIdAttr(Decl *D, const ParsedAttr &AL);
void handleSV_DispatchThreadIDAttr(Decl *D, const ParsedAttr &AL);
void handleSV_GroupThreadIDAttr(Decl *D, const ParsedAttr &AL);
void handleSV_GroupIDAttr(Decl *D, const ParsedAttr &AL);
@@ -156,7 +159,7 @@ class SemaHLSL : public SemaBase {
QualType getInoutParameterType(QualType Ty);
bool transformInitList(const InitializedEntity &Entity, InitListExpr *Init);
-
+ bool handleInitialization(VarDecl *VDecl, Expr *&Init);
void deduceAddressSpace(VarDecl *Decl);
private:
diff --git a/clang/lib/Basic/Attributes.cpp b/clang/lib/Basic/Attributes.cpp
index 905046685934b..5f74365f0ed00 100644
--- a/clang/lib/Basic/Attributes.cpp
+++ b/clang/lib/Basic/Attributes.cpp
@@ -213,7 +213,8 @@ getScopeFromNormalizedScopeName(StringRef ScopeName) {
.Case("vk", AttributeCommonInfo::Scope::VK)
.Case("msvc", AttributeCommonInfo::Scope::MSVC)
.Case("omp", AttributeCommonInfo::Scope::OMP)
- .Case("riscv", AttributeCommonInfo::Scope::RISCV);
+ .Case("riscv", AttributeCommonInfo::Scope::RISCV)
+ .Case("vk", AttributeCommonInfo::Scope::HLSL);
}
unsigned AttributeCommonInfo::calculateAttributeSpellingListIndex() const {
diff --git a/clang/lib/CodeGen/CGHLSLBuiltins.cpp b/clang/lib/CodeGen/CGHLSLBuiltins.cpp
index abebc201808b0..74b5f92638600 100644
--- a/clang/lib/CodeGen/CGHLSLBuiltins.cpp
+++ b/clang/lib/CodeGen/CGHLSLBuiltins.cpp
@@ -12,6 +12,7 @@
#include "CGBuiltin.h"
#include "CGHLSLRuntime.h"
+#include "CodeGenFunction.h"
using namespace clang;
using namespace CodeGen;
@@ -774,6 +775,77 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
return EmitRuntimeCall(
Intrinsic::getOrInsertDeclaration(&CGM.getModule(), ID));
}
+ case Builtin::BI__builtin_get_spirv_spec_constant_bool:
+ case Builtin::BI__builtin_get_spirv_spec_constant_short:
+ case Builtin::BI__builtin_get_spirv_spec_constant_ushort:
+ case Builtin::BI__builtin_get_spirv_spec_constant_int:
+ case Builtin::BI__builtin_get_spirv_spec_constant_uint:
+ case Builtin::BI__builtin_get_spirv_spec_constant_longlong:
+ case Builtin::BI__builtin_get_spirv_spec_constant_ulonglong:
+ case Builtin::BI__builtin_get_spirv_spec_constant_half:
+ case Builtin::BI__builtin_get_spirv_spec_constant_float:
+ case Builtin::BI__builtin_get_spirv_spec_constant_double: {
+ llvm::Function *SpecConstantFn = getSpecConstantFunction(E->getType());
+ llvm::Value *SpecId = EmitScalarExpr(E->getArg(0));
+ llvm::Value *DefaultVal = EmitScalarExpr(E->getArg(1));
+ llvm::Value *Args[] = {SpecId, DefaultVal};
+ return Builder.CreateCall(SpecConstantFn, Args);
+ }
}
return nullptr;
}
+
+llvm::Function *clang::CodeGen::CodeGenFunction::getSpecConstantFunction(
+ const clang::QualType &SpecConstantType) {
+
+ // Find or create the declaration for the function.
+ llvm::Module *M = &CGM.getModule();
+ std::string MangledName = getSpecConstantFunctionName(SpecConstantType);
+ llvm::Function *SpecConstantFn = M->getFunction(MangledName);
+
+ if (!SpecConstantFn) {
+ llvm::Type *IntType = ConvertType(getContext().IntTy);
+ llvm::Type *RetTy = ConvertType(SpecConstantType);
+ llvm::Type *ArgTypes[] = {IntType, RetTy};
+ llvm::FunctionType *FnTy = llvm::FunctionType::get(RetTy, ArgTypes, false);
+ SpecConstantFn = llvm::Function::Create(
+ FnTy, llvm::GlobalValue::ExternalLinkage, MangledName, M);
+ }
+ return SpecConstantFn;
+}
+
+std::string clang::CodeGen::CodeGenFunction::getSpecConstantFunctionName(
+ const clang::QualType &SpecConstantType) {
+ // The parameter types for our conceptual intrinsic function.
+ ASTContext &Context = getContext();
+ QualType ClangParamTypes[] = {Context.IntTy, SpecConstantType};
+
+ // Create a temporary FunctionDecl for the builtin fuction. It won't be
+ // added to the AST.
+ FunctionProtoType::ExtProtoInfo EPI;
+ QualType FnType =
+ Context.getFunctionType(SpecConstantType, ClangParamTypes, EPI);
+ DeclarationName FuncName = &Context.Idents.get("__spirv_SpecConstant");
+ FunctionDecl *FnDeclForMangling = FunctionDecl::Create(
+ Context, Context.getTranslationUnitDecl(), SourceLocation(),
+ SourceLocation(), FuncName, FnType, /*TSI=*/nullptr, SC_Extern);
+
+ // Attach the created parameter declarations to the function declaration.
+ SmallVector<ParmVarDecl *, 2> ParamDecls;
+ for (QualType ParamType : ClangParamTypes) {
+ ParmVarDecl *PD = ParmVarDecl::Create(
+ Context, FnDeclForMangling, SourceLocation(), SourceLocation(),
+ /*IdentifierInfo*/ nullptr, ParamType, /*TSI*/ nullptr, SC_None,
+ /*DefaultArg*/ nullptr);
+ ParamDecls.push_back(PD);
+ }
+ FnDeclForMangling->setParams(ParamDecls);
+
+ // Get the mangled name.
+ std::string Name;
+ llvm::raw_string_ostream MangledNameStream(Name);
+ MangleContext *Mangler = Context.createMangleContext();
+ Mangler->mangleName(FnDeclForMangling, MangledNameStream);
+ MangledNameStream.flush();
+ return Name;
+}
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index a5ab9df01dba9..badc9feeb8c2b 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -4850,6 +4850,17 @@ class CodeGenFunction : public CodeGenTypeCache {
llvm::Value *EmitAMDGPUBuiltinExpr(unsigned BuiltinID, const CallExpr *E);
llvm::Value *EmitHLSLBuiltinExpr(unsigned BuiltinID, const CallExpr *E,
ReturnValueSlot ReturnValue);
+
+ // Returns a builtin function that the SPIR-V backend will expand into a spec
+ // constant.
+ llvm::Function *
+ getSpecConstantFunction(const clang::QualType &SpecConstantType);
+
+ // Returns the mangled name for a builtin function that the SPIR-V backend
+ // will expand into a spec Constant.
+ std::string
+ getSpecConstantFunctionName(const clang::QualType &SpecConstantType);
+
llvm::Value *EmitDirectXBuiltinExpr(unsigned BuiltinID, const CallExpr *E);
llvm::Value *EmitSPIRVBuiltinExpr(unsigned BuiltinID, const CallExpr *E);
llvm::Value *EmitScalarOrConstFoldImmArg(unsigned ICEArguments, unsigned Idx,
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index bbd63372c168b..9d09eec26f7a2 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2889,6 +2889,8 @@ static bool mergeDeclAttribute(Sema &S, NamedDecl *D,
NewAttr = S.HLSL().mergeWaveSizeAttr(D, *WS, WS->getMin(), WS->getMax(),
WS->getPreferred(),
WS->getSpelledArgsCount());
+ else if (const auto *CI = dyn_cast<HLSLVkConstantIdAttr>(Attr))
+ NewAttr = S.HLSL().mergeVkConstantIdAttr(D, *CI, CI->getId());
else if (const auto *SA = dyn_cast<HLSLShaderAttr>(Attr))
NewAttr = S.HLSL().mergeShaderAttr(D, *SA, SA->getType());
else if (isa<SuppressAttr>(Attr))
@@ -13755,6 +13757,10 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
return;
}
+ if (getLangOpts().HLSL)
+ if (!HLSL().handleInitialization(VDecl, Init))
+ return;
+
// Get the decls type and save a reference for later, since
// CheckInitializerTypes may change it.
QualType DclT = VDecl->getType(), SavT = DclT;
@@ -14215,6 +14221,14 @@ void Sema::ActOnUninitializedDecl(Decl *RealDecl) {
}
}
+ // HLSL variable with the `vk::constant_id` attribute must be initialized.
+ if (!Var->isInvalidDecl() && Var->hasAttr<HLSLVkConstantIdAttr>()) {
+ Diag(Var->getLocation(),
+ diag::err_specialization_const_missing_initializer);
+ Var->setInvalidDecl();
+ return;
+ }
+
if (!Var->isInvalidDecl() && RealDecl->hasAttr<LoaderUninitializedAttr>()) {
if (Var->getStorageClass() == SC_Extern) {
Diag(Var->getLocation(), diag::err_loader_uninitialized_extern_decl)
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index da0e3265767d8..e49bdda1a402b 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -7560,6 +7560,9 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
case ParsedAttr::AT_HLSLVkExtBuiltinInput:
S.HLSL().handleVkExtBuiltinInputAttr(D, AL);
break;
+ case ParsedAttr::AT_HLSLVkConstantId:
+ S.HLSL().handleVkConstantIdAttr(D, AL);
+ break;
case ParsedAttr::AT_HLSLSV_GroupThreadID:
S.HLSL().handleSV_GroupThreadIDAttr(D, AL);
break;
diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index 9065cc5a1d4a5..5764507f35882 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -119,6 +119,40 @@ static ResourceClass getResourceClass(RegisterType RT) {
llvm_unreachable("unexpected RegisterType value");
}
+static Builtin::ID getSpecConstBuiltinId(QualType Type) {
+ const auto *BT = dyn_cast<BuiltinType>(Type);
+ if (!BT) {
+ if (!Type->isEnumeralType())
+ return Builtin::NotBuiltin;
+ return Builtin::BI__builtin_get_spirv_spec_constant_int;
+ }
+
+ switch (BT->getKind()) {
+ case BuiltinType::Bool:
+ return Builtin::BI__builtin_get_spirv_spec_constant_bool;
+ case BuiltinType::Short:
+ return Builtin::BI__builtin_get_spirv_spec_constant_short;
+ case BuiltinType::Int:
+ return Builtin::BI__builtin_get_spirv_spec_constant_int;
+ case BuiltinType::LongLong:
+ return Builtin::BI__builtin_get_spirv_spec_constant_longlong;
+ case BuiltinType::UShort:
+ return Builtin::BI__builtin_get_spirv_spec_constant_ushort;
+ case BuiltinType::UInt:
+ return Builtin::BI__builtin_get_spirv_spec_constant_uint;
+ case BuiltinType::ULongLong:
+ return Builtin::BI__builtin_get_spirv_spec_constant_ulonglong;
+ case BuiltinType::Half:
+ return Builtin::BI__builtin_get_spirv_spec_constant_half;
+ case BuiltinType::Float:
+ return Builtin::BI__builtin_get_spirv_spec_constant_float;
+ case BuiltinType::Double:
+ return Builtin::BI__builtin_get_spirv_spec_constant_double;
+ default:
+ return Builtin::NotBuiltin;
+ }
+}
+
DeclBindingInfo *ResourceBindings::addDeclBindingInfo(const VarDecl *VD,
ResourceClass ResClass) {
assert(getDeclBindingInfo(VD, ResClass) == nullptr &&
@@ -607,6 +641,41 @@ HLSLWaveSizeAttr *SemaHLSL::mergeWaveSizeAttr(Decl *D,
return Result;
}
+HLSLVkConstantIdAttr *
+SemaHLSL::mergeVkConstantIdAttr(Decl *D, const AttributeCommonInfo &AL,
+ int Id) {
+
+ auto &TargetInfo = getASTContext().getTargetInfo();
+ if (TargetInfo.getTriple().getArch() != llvm::Triple::spirv) {
+ Diag(AL.getLoc(), diag::warn_attribute_ignored) << AL;
+ return nullptr;
+ }
+
+ auto *VD = cast<VarDecl>(D);
+
+ if (getSpecConstBuiltinId(VD->getType()) == Builtin::NotBuiltin) {
+ Diag(VD->getLocation(), diag::err_specialization_const_is_not_int_or_float);
+ return nullptr;
+ }
+
+ if (!VD->getType().isConstQualified()) {
+ Diag(VD->getLocation(), diag::err_specialization_const_missing_const);
+ return nullptr;
+ }
+
+ if (HLSLVkConstantIdAttr *CI = D->getAttr<HLSLVkConstantIdAttr>()) {
+ if (CI->getId() != Id) {
+ Diag(CI->getLocation(), diag::err_hlsl_attribute_param_mismatch) << AL;
+ Diag(AL.getLoc(), diag::note_conflicting_attribute);
+ }
+ return nullptr;
+ }
+
+ HLSLVkConstantIdAttr *Result =
+ ::new (getASTContext()) HLSLVkConstantIdAttr(getASTContext(), AL, Id);
+ return Result;
+}
+
HLSLShaderAttr *
SemaHLSL::mergeShaderAttr(Decl *D, const AttributeCommonInfo &AL,
llvm::Triple::EnvironmentType ShaderType) {
@@ -1125,6 +1194,15 @@ void SemaHLSL::handleVkExtBuiltinInputAttr(Decl *D, const ParsedAttr &AL) {
HLSLVkExtBuiltinInputAttr(getASTContext(), AL, ID));
}
+void SemaHLSL::handleVkConstantIdAttr(Decl *D, const ParsedAttr &AL) {
+ uint32_t Id;
+ if (!SemaRef.checkUInt32Argument(AL, AL.getArgAsExpr(0), Id))
+ return;
+ HLSLVkConstantIdAttr *NewAttr = mergeVkConstantIdAttr(D, AL, Id);
+ if (NewAttr)
+ D->addAttr(NewAttr);
+}
+
bool SemaHLSL::diagnoseInputIDType(QualType T, const ParsedAttr &AL) {
const auto *VT = T->getAs<VectorType>();
@@ -3154,6 +3232,7 @@ static bool IsDefaultBufferConstantDecl(VarDecl *VD) {
return VD->getDeclContext()->isTranslationUnit() &&
QT.getAddressSpace() == LangAS::Default &&
VD->getStorageClass() != SC_Static &&
+ !VD->hasAttr<HLSLVkConstantIdAttr>() &&
!isInvalidConstantBufferLeafElementType(QT.getTypePtr());
}
@@ -3221,7 +3300,8 @@ void SemaHLSL::ActOnVariableDeclarator(VarDecl *VD) {
const Type *VarType = VD->getType().getTypePtr();
while (VarType->isArrayType())
VarType = VarType->getArrayElementTypeNoTypeQual();
- if (VarType->isHLSLResourceRecord()) {
+ if (VarType->isHLSLResourceRecord() ||
+ VD->hasAttr<HLSLVkConstantIdAttr>()) {
// Make the variable for resources static. The global externally visible
// storage is accessed through the handle, which is a member. The variable
// itself is not externally visible.
@@ -3644,3 +3724,41 @@ bool SemaHLSL::transformInitList(const InitializedEntity &Entity,
Init->updateInit(Ctx, I, NewInit->getInit(I));
return true;
}
+
+bool SemaHLSL::handleInitialization(VarDecl *VDecl, Expr *&Init) {
+ const HLSLVkConstantIdAttr *ConstIdAttr =
+ VDecl->getAttr<HLSLVkConstantIdAttr>();
+ if (!ConstIdAttr)
+ return true;
+
+ ASTContext &Context = SemaRef.getASTContext();
+
+ APValue InitValue;
+ if (!Init->isCXX11ConstantExpr(Context, &InitValue)) {
+ Diag(VDecl->getLocation(), diag::err_specialization_const_lit_init);
+ VDecl->setInvalidDecl();
+ return false;
+ }
+
+ Builtin::ID BID = getSpecConstBuiltinId(VDecl->getType());
+
+ // Argument 1: The ID from the attribute
+ int ConstantID = ConstIdAttr->getId();
+ llvm::APInt IDVal(Context.getIntWidth(Context.IntTy), ConstantID);
+ Expr *IdExpr = IntegerLiteral::Create(Context, IDVal, Context.IntTy,
+ ConstIdAttr->getLocation());
+
+ SmallVector<Expr *, 2> Args = {IdExpr, Init};
+ Expr *C = SemaRef.BuildBuiltinCallExpr(Init->getExprLoc(), BID, Args);
+ if (C->getType()->getCanonicalTypeUnqualified() !=
+ VDecl->getType()->getCanonicalTypeUnqualified()) {
+ C = SemaRef
+ .BuildCStyleCastExpr(SourceLocation(),
+ Context.getTrivialTypeSourceInfo(
+ Init->getType(), Init->getExprLoc()),
+ SourceLocation(), C)
+ .get();
+ }
+ Init = C;
+ return true;
+}
diff --git a/clang/test/AST/HLSL/vk.spec-constant.usage.hlsl b/clang/test/AST/HLSL/vk.spec-constant.usage.hlsl
new file mode 100644
index 0000000000000..c0955c1ea7b43
--- /dev/null
+++ b/clang/test/AST/HLSL/vk.spec-constant.usage.hlsl
@@ -0,0 +1,130 @@
+// RUN: %clang_cc1 -finclude-default-header -triple spirv-unknown-vulkan-compute -x hlsl -ast-dump -o - %s | FileCheck %s
+
+// CHECK: VarDecl {{.*}} bool_const 'const hlsl_private bool' static cinit
+// CHECK-NEXT: CallExpr {{.*}} 'bool'
+// CHECK-NEXT: ImplicitCastExpr {{.*}} 'bool (*)(unsigned int, bool) noexcept' <FunctionToPointerDecay>
+// CHECK-NEXT: DeclRefExpr {{.*}} 'bool (unsigned int, bool) noexcept' lvalue Function {{.*}} '__builtin_get_spirv_spec_constant_bool' 'bool (unsigned int, bool) noexcept'
+// CHECK-NEXT: ImplicitCastExpr {{.*}...
[truncated]
``````````
</details>
https://github.com/llvm/llvm-project/pull/143544
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