[SPIR-V] Fix SPIRVEmitIntrinsics undefined behavior (#123625)

Before this change InstrSet in SPIRVEmitIntrinsics was uninitialized
before running runOnFunction. This change adds a new function
getPreferredInstructionSet in SPIRVSubtarget.

Author: michalpaszkowski

llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp

@@ -544,13 +544,7 @@ bool SPIRVCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
   const auto *ST = static_cast<const SPIRVSubtarget *>(&MF.getSubtarget());
 
   bool isFunctionDecl = CF && CF->isDeclaration();
-  bool canUseOpenCL = ST->canUseExtInstSet(SPIRV::InstructionSet::OpenCL_std);
-  bool canUseGLSL = ST->canUseExtInstSet(SPIRV::InstructionSet::GLSL_std_450);
-  assert(canUseGLSL != canUseOpenCL &&
-         "Scenario where both sets are enabled is not supported.");
-
-  if (isFunctionDecl && !DemangledName.empty() &&
-      (canUseGLSL || canUseOpenCL)) {
+  if (isFunctionDecl && !DemangledName.empty()) {
     if (ResVReg.isValid()) {
       if (!GR->getSPIRVTypeForVReg(ResVReg)) {
         const Type *RetTy = OrigRetTy;
@@ -607,11 +601,9 @@ bool SPIRVCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
                                    GR->getPointerSize()));
       }
     }
-    auto instructionSet = canUseOpenCL ? SPIRV::InstructionSet::OpenCL_std
-                                       : SPIRV::InstructionSet::GLSL_std_450;
     if (auto Res =
-            SPIRV::lowerBuiltin(DemangledName, instructionSet, MIRBuilder,
-                                ResVReg, OrigRetTy, ArgVRegs, GR))
+            SPIRV::lowerBuiltin(DemangledName, ST->getPreferredInstructionSet(),
+                                MIRBuilder, ResVReg, OrigRetTy, ArgVRegs, GR))
       return *Res;
   }
 

llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp

@@ -74,7 +74,6 @@ class SPIRVEmitIntrinsics
   DenseMap<Instruction *, Constant *> AggrConsts;
   DenseMap<Instruction *, Type *> AggrConstTypes;
   DenseSet<Instruction *> AggrStores;
-  SPIRV::InstructionSet::InstructionSet InstrSet;
 
   // map of function declarations to <pointer arg index => element type>
   DenseMap<Function *, SmallVector<std::pair<unsigned, Type *>>> FDeclPtrTys;
@@ -896,8 +895,9 @@ bool SPIRVEmitIntrinsics::deduceOperandElementTypeCalledFunction(
       getOclOrSpirvBuiltinDemangledName(CalledF->getName());
   if (DemangledName.length() > 0 &&
       !StringRef(DemangledName).starts_with("llvm.")) {
-    auto [Grp, Opcode, ExtNo] =
-        SPIRV::mapBuiltinToOpcode(DemangledName, InstrSet);
+    const SPIRVSubtarget &ST = TM->getSubtarget<SPIRVSubtarget>(*CalledF);
+    auto [Grp, Opcode, ExtNo] = SPIRV::mapBuiltinToOpcode(
+        DemangledName, ST.getPreferredInstructionSet());
     if (Opcode == SPIRV::OpGroupAsyncCopy) {
       for (unsigned i = 0, PtrCnt = 0; i < CI->arg_size() && PtrCnt < 2; ++i) {
         Value *Op = CI->getArgOperand(i);
@@ -2317,8 +2317,6 @@ bool SPIRVEmitIntrinsics::runOnFunction(Function &Func) {
 
   const SPIRVSubtarget &ST = TM->getSubtarget<SPIRVSubtarget>(Func);
   GR = ST.getSPIRVGlobalRegistry();
-  InstrSet = ST.isOpenCLEnv() ? SPIRV::InstructionSet::OpenCL_std
-                              : SPIRV::InstructionSet::GLSL_std_450;
 
   if (!CurrF)
     HaveFunPtrs =
@@ -2475,8 +2473,9 @@ void SPIRVEmitIntrinsics::parseFunDeclarations(Module &M) {
     if (DemangledName.empty())
       continue;
     // allow only OpGroupAsyncCopy use case at the moment
-    auto [Grp, Opcode, ExtNo] =
-        SPIRV::mapBuiltinToOpcode(DemangledName, InstrSet);
+    const SPIRVSubtarget &ST = TM->getSubtarget<SPIRVSubtarget>(F);
+    auto [Grp, Opcode, ExtNo] = SPIRV::mapBuiltinToOpcode(
+        DemangledName, ST.getPreferredInstructionSet());
     if (Opcode != SPIRV::OpGroupAsyncCopy)
       continue;
     // find pointer arguments

llvm/lib/Target/SPIRV/SPIRVSubtarget.cpp

@@ -111,6 +111,14 @@ bool SPIRVSubtarget::canUseExtInstSet(
   return AvailableExtInstSets.contains(E);
 }
 
+SPIRV::InstructionSet::InstructionSet
+SPIRVSubtarget::getPreferredInstructionSet() const {
+  if (isOpenCLEnv())
+    return SPIRV::InstructionSet::OpenCL_std;
+  else
+    return SPIRV::InstructionSet::GLSL_std_450;
+}
+
 bool SPIRVSubtarget::isAtLeastSPIRVVer(VersionTuple VerToCompareTo) const {
   return isAtLeastVer(SPIRVVersion, VerToCompareTo);
 }

llvm/lib/Target/SPIRV/SPIRVSubtarget.h

@@ -96,6 +96,7 @@ class SPIRVSubtarget : public SPIRVGenSubtargetInfo {
   }
   bool canUseExtension(SPIRV::Extension::Extension E) const;
   bool canUseExtInstSet(SPIRV::InstructionSet::InstructionSet E) const;
+  SPIRV::InstructionSet::InstructionSet getPreferredInstructionSet() const;
 
   SPIRVGlobalRegistry *getSPIRVGlobalRegistry() const { return GR.get(); }