[globalopt] Teach to look through `addrspacecast`.

[hliao]

Summary

• so that global variables in numbered address spaces could be properly analyzed.

[hliao]

Kindly PING for review.

[bkramer]

This should be safe. Looks good.

llvm/lib/Transforms/Utils/GlobalStatus.cpp

if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(UR)) {
               // noop.
             } else {
               GS.StoredType = GlobalStatus::Stored;
             }
           } else {
             GS.StoredType = GlobalStatus::Stored;
           }
         }
-      } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
+      } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I) ||
+                 isa<AddrSpaceCastInst>(I)) {
         // Skip over bitcasts and GEPs; we don't care about the type or offset
         // of the pointer.
         if (analyzeGlobalAux(I, GS, VisitedUsers))
           return true;
       } else if (isa<SelectInst>(I) || isa<PHINode>(I)) {
         // Look through selects and PHIs to find if the pointer is
         // conditionally accessed. Make sure we only visit an instruction
         // once; otherwise, we can get infinite recursion or exponential

llvm/test/Transforms/GlobalOpt/unnamed-addr.ll

 ; RUN: opt -globalopt -S < %s | FileCheck %s
 
 @a = internal global i32 0, align 4
 @b = internal global i32 0, align 4
 @c = internal global i32 0, align 4
 @d = internal constant [4 x i8] c"foo\00", align 1
 @e = linkonce_odr global i32 0
+@f = internal addrspace(3) global float undef, align 4
 
 ; CHECK: @a = internal global i32 0, align 4
 ; CHECK: @b = internal global i32 0, align 4
 ; CHECK: @c = internal unnamed_addr global i32 0, align 4
 ; CHECK: @d = internal unnamed_addr constant [4 x i8] c"foo\00", align 1
 ; CHECK: @e = linkonce_odr local_unnamed_addr global i32 0
+; CHECK: @f = internal unnamed_addr addrspace(3) global float undef, align 4
 
 ; CHECK: define internal fastcc void @used_internal() unnamed_addr {
 define internal void @used_internal() {
   ret void
 }
 
 define i32 @get_e() {
        call void @used_internal()
return:
   ret i32 1
 }
 
 define i32 @zed() {
 entry:
   %tmp1 = load i32, i32* @c, align 4
   ret i32 %tmp1
 }
+
+define float @use_addrspace_cast_for_load() {
+  %p = addrspacecast float addrspace(3)* @f to float*
+  %v = load float, float* %p
+  ret float %v
+}
+
+define void @use_addrspace_cast_for_store(float %x) {
+  %p = addrspacecast float addrspace(3)* @f to float*
+  store float %x, float* %p
+  ret void
+}