[llvm] [SPIRV] Add support for pointers to functions with aggregate args/returns as global variables / constant initialisers (PR #169595)

[Juan Manuel Martinez Caamaño via llvm-commits]

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@@ -543,11 +558,76 @@ SPIRVPrepareFunctions::removeAggregateTypesFromSignature(Function *F) {
   return NewF;
 }
 
+// Mutates indirect callsites iff if aggregate argument/return types are present
+// with the types replaced by i32 types. The change in types is noted in
+// 'spv.mutated_callsites' metadata for later restoration.
+bool SPIRVPrepareFunctions::removeAggregateTypesFromCalls(Function *F) {
+  if (F->isDeclaration() || F->isIntrinsic())
+    return false;
+
+  SmallVector<std::pair<CallBase *, FunctionType *>> Calls;
+  for (auto &&BB : *F) {
+    for (auto &&I : BB) {
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jmmartinez wrote:

Maybe use instructions to reduce the indentation.
```suggestion
  for (auto &&I : instructions(F)) {
```

https://github.com/llvm/llvm-project/pull/169595