[InstCombine] Teach isAllocSiteRemovable to look through addrspacecasts

[reames]

LGTM

llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp

do {
     Instruction *PI = Worklist.pop_back_val();
     for (User *U : PI->users()) {
       Instruction *I = cast<Instruction>(U);
       switch (I->getOpcode()) {
       default:
         // Give up the moment we see something we can't handle.
         return false;
 
+      case Instruction::AddrSpaceCast:
       case Instruction::BitCast:
       case Instruction::GetElementPtr:
         Users.emplace_back(I);
         Worklist.push_back(I);
         continue;
 
       case Instruction::ICmp: {
         ICmpInst *ICI = cast<ICmpInst>(I);
for (unsigned i = 0, e = Users.size(); i != e; ++i) {
         continue;
 
       Instruction *I = cast<Instruction>(&*Users[i]);
 
       if (ICmpInst *C = dyn_cast<ICmpInst>(I)) {
         replaceInstUsesWith(*C,
                             ConstantInt::get(Type::getInt1Ty(C->getContext()),
                                              C->isFalseWhenEqual()));
-      } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
+      } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I) ||
+                 isa<AddrSpaceCastInst>(I)) {
         replaceInstUsesWith(*I, UndefValue::get(I->getType()));
       }
       eraseInstFromFunction(*I);
     }
 
     if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) {
       // Replace invoke with a NOP intrinsic to maintain the original CFG
       Module *M = II->getModule();

llvm/trunk/test/Transforms/InstCombine/alloca.ll

 ; CHECK-LABEL: @test4(
 ; CHECK: = zext i32 %n to i64
 ; CHECK: %A = alloca i32, i64 %
 define i32* @test4(i32 %n) {
   %A = alloca i32, i32 %n
   ret i32* %A
 }
 
-; Allocas which are only used by GEPs, bitcasts, and stores (transitively)
-; should be deleted.
+; Allocas which are only used by GEPs, bitcasts, addrspacecasts, and stores
+; (transitively) should be deleted.
 define void @test5() {
 ; CHECK-LABEL: @test5(
 ; CHECK-NOT: alloca
 ; CHECK-NOT: store
 ; CHECK: ret
 
 entry:
   %a = alloca { i32 }
   %b = alloca i32*
+  %c = alloca i32
   %a.1 = getelementptr { i32 }, { i32 }* %a, i32 0, i32 0
   store i32 123, i32* %a.1
   store i32* %a.1, i32** %b
   %b.1 = bitcast i32** %b to i32*
   store i32 123, i32* %b.1
   %a.2 = getelementptr { i32 }, { i32 }* %a, i32 0, i32 0
   store atomic i32 2, i32* %a.2 unordered, align 4
   %a.3 = getelementptr { i32 }, { i32 }* %a, i32 0, i32 0
   store atomic i32 3, i32* %a.3 release, align 4
   %a.4 = getelementptr { i32 }, { i32 }* %a, i32 0, i32 0
   store atomic i32 4, i32* %a.4 seq_cst, align 4
+  %c.1 = addrspacecast i32* %c to i32 addrspace(1)*
+  store i32 123, i32 addrspace(1)* %c.1
   ret void
 }
 
 declare void @f(i32* %p)
 
 ; Check that we don't delete allocas in some erroneous cases.
 define void @test6() {
 ; CHECK-LABEL: @test6(