[SROA][Mem2Reg] Do not crash on alloca + addrspacecast

[jdoerfert]

Summary

SROA knows that it can look through addrspacecast but
PromoteMemoryToRegister did not handle them. This caused an assertion
error for the test case, exposed while running
Transforms/PhaseOrdering/inlining-alignment-assumptions.ll with D83978
applied.

[arsenm]

llvm/test/Transforms/SROA/alloca_addrspace.ll

2–3

This is also covered by SROA tests, should this go in test/Mem2Reg

20

Also could use a negative case

[jdoerfert]

Split test and merge the SROA part into existing test case

llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp

if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
         return false;
     } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
       if (GEPI->getType() != Type::getInt8PtrTy(U->getContext(), AS))
         return false;
       if (!GEPI->hasAllZeroIndices())
         return false;
       if (!onlyUsedByLifetimeMarkers(GEPI))
         return false;
+    } else if (const AddrSpaceCastInst *ASCI = dyn_cast<AddrSpaceCastInst>(U)) {
+      if (!onlyUsedByLifetimeMarkers(ASCI))
+        return false;
     } else {
       return false;
     }
   }
 
   return true;
 }
 

llvm/test/Transforms/SROA/alloca_addrspace.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -sroa -S | FileCheck %s
+; RUN: opt < %s -passes=sroa -S | FileCheck %s
+; RUN: opt < %s -mem2reg -S | FileCheck %s
+; RUN: opt < %s -passes=mem2reg -S | FileCheck %s
+
+; Do not crash ;)
+
+target datalayout = "e-p:64:64-p5:32:32-A5"
+
+define amdgpu_kernel void @addressspace_alloca() {
+; CHECK-LABEL: @addressspace_alloca(
+; CHECK-NEXT:    ret void
+;
+  %alloca = alloca i8, align 8, addrspace(5)
+  %cast = addrspacecast i8 addrspace(5)* %alloca to i8*
+  call void @llvm.lifetime.start.p0i8(i64 2, i8* %cast)
+  ret void
+}
+
+declare void @llvm.lifetime.start.p0i8(i64 %size, i8* nocapture %ptr)