[LLVM-15] Recover non-struct pointee types from demangling func args

The StructType* overload of getParameterTypes returned nullptr for pointer
arguments whose pointee type is a primitive (e.g. bfloat16), preventing
SPIRVTypeScavenger from inferring the correct type for such arguments.

Add a Type* overload as the primary implementation and forward the existing
StructType* overload to it for backward compatibility.

AI-assisted: Claude Sonnet 4.6 (commercial SaaS)

Author: vmaksimo

lib/SPIRV/SPIRVInternal.h

@@ -998,9 +998,12 @@ bool containsUnsignedAtomicType(StringRef Name);
 std::string mangleBuiltin(StringRef UniqName, ArrayRef<Type *> ArgTypes,
                           BuiltinFuncMangleInfo *BtnInfo);
 
-/// Extract the pointee types of arguments from a mangled function name. If the
-/// corresponding type is not a pointer to a struct type, its value will be a
-/// nullptr instead.
+/// Extract the pointee types of arguments from a mangled function name,
+/// including non-struct types such as bfloat16. Unknown types are nullptr.
+void getParameterTypes(Function *F, SmallVectorImpl<Type *> &ArgTys);
+
+/// Struct-typed variant of getParameterTypes. Non-struct pointee types (e.g.
+/// bfloat) are returned as nullptr.
 void getParameterTypes(Function *F, SmallVectorImpl<StructType *> &ArgTys);
 inline void getParameterTypes(CallInst *CI,
                               SmallVectorImpl<StructType *> &ArgTys) {

lib/SPIRV/SPIRVTypeScavenger.cpp

@@ -229,7 +229,7 @@ void SPIRVTypeScavenger::deduceFunctionType(Function &F) {
   // If the function is a mangled name, try to recover types from the Itanium
   // name mangling.
   if (F.getName().startswith("_Z")) {
-    SmallVector<StructType *, 8> ParameterTypes;
+    SmallVector<Type *, 8> ParameterTypes;
     getParameterTypes(&F, ParameterTypes);
     for (Argument *Arg : PointerArgs) {
       if (auto *Ty = ParameterTypes[Arg->getArgNo()]) {

lib/SPIRV/SPIRVUtil.cpp

@@ -779,7 +779,7 @@ static std::string demangleBuiltinOpenCLTypeName(StringRef MangledStructName) {
   return LlvmStructName;
 }
 
-void getParameterTypes(Function *F, SmallVectorImpl<StructType *> &ArgTys) {
+void getParameterTypes(Function *F, SmallVectorImpl<Type *> &ArgTys) {
   // If there's no mangled name, we can't do anything. Also, if there's no
   // parameters, do nothing.
   StringRef Name = F->getName();
@@ -799,7 +799,7 @@ void getParameterTypes(Function *F, SmallVectorImpl<StructType *> &ArgTys) {
       assert(!HasSret && &Arg == F->getArg(0) &&
              "sret parameter should only appear on the first argument");
       HasSret = true;
-      ArgTys.push_back(dyn_cast<StructType>(Ty));
+      ArgTys.push_back(Ty);
     } else {
       ArgTys.push_back(nullptr);
     }
@@ -866,7 +866,7 @@ void getParameterTypes(Function *F, SmallVectorImpl<StructType *> &ArgTys) {
     }
 
     for (StringRef Arg : ArgParams) {
-      StructType *Pointee = nullptr;
+      Type *Pointee = nullptr;
       if (Arg.endswith("*") && !Arg.endswith("**")) {
         // Strip off address space and other qualifiers.
         StringRef MangledStructName = Arg.split(' ').first;
@@ -897,6 +897,13 @@ void getParameterTypes(Function *F, SmallVectorImpl<StructType *> &ArgTys) {
   free(Buf);
 }
 
+void getParameterTypes(Function *F, SmallVectorImpl<StructType *> &ArgTys) {
+  SmallVector<Type *, 8> Tys;
+  getParameterTypes(F, Tys);
+  for (Type *T : Tys)
+    ArgTys.push_back(dyn_cast_or_null<StructType>(T));
+}
+
 // This is a transitional helper function to fill in mangling information for
 // mangleBuiltin while all the calls to mutateCallInst are being transitioned.
 static void typeMangle(BuiltinFuncMangleInfo *Mangle, ArrayRef<Value *> Args) {