[nfc] Accept addrspacecast allocas in InitTempAlloca

[JonChesterfield]

Summary

[nfc] Accept addrspacecast allocas in InitTempAlloca
Changes the precondition to be slightly more permissive. Useful for amdgcn where
allocas are created with a cast to an address space.

[arsenm]

Needs test?

[JonChesterfield]

In D78495#1992404, @arsenm wrote:

Needs test?

I'm not sure how to write said test. How do we normally hit asserts from the clang test suite?

This fires a lot in the openmp on amdgcn downstream branch, but I'm happy carrying this as a local patch until the rest of the clang change can be put up for review if preferred.

[rjmccall]

You're not testing an assertion, you're testing that code is generated correctly for some file on amdgcn. Just write an ordinary IR-generation test that currently crashes and this test fixes.

This is not an NFC change.

[JonChesterfield]

No problem. This isn't on the live path - the function is mostly called from openmp codegen and clang doesn't target openmp/amdgcn just yet. I'll roll this change into the codegen patch to enable that.

clang/lib/CodeGen/CGExpr.cpp

 Address CodeGenFunction::CreateDefaultAlignTempAlloca(llvm::Type *Ty,
                                                       const Twine &Name) {
   CharUnits Align =
     CharUnits::fromQuantity(CGM.getDataLayout().getABITypeAlignment(Ty));
   return CreateTempAlloca(Ty, Align, Name);
 }
 
 void CodeGenFunction::InitTempAlloca(Address Var, llvm::Value *Init) {
-  assert(isa<llvm::AllocaInst>(Var.getPointer()));
-  auto *Store = new llvm::StoreInst(Init, Var.getPointer());
+  auto *Alloca = Var.getPointer();
+  assert(isa<llvm::AllocaInst>(Alloca) ||
+         (isa<llvm::AddrSpaceCastInst>(Alloca) &&
+          isa<llvm::AllocaInst>(
+              cast<llvm::AddrSpaceCastInst>(Alloca)->getPointerOperand())));
+  auto *Store = new llvm::StoreInst(Init, Alloca);
   Store->setAlignment(Var.getAlignment().getAsAlign());
   llvm::BasicBlock *Block = AllocaInsertPt->getParent();
   Block->getInstList().insertAfter(AllocaInsertPt->getIterator(), Store);
 }
 
 Address CodeGenFunction::CreateIRTemp(QualType Ty, const Twine &Name) {
   CharUnits Align = getContext().getTypeAlignInChars(Ty);
   return CreateTempAlloca(ConvertType(Ty), Align, Name);