[InferAddressSpaces] Fix assertion about null pointer

[yaxunl]

Summary

InferAddressSpaces does not check address space in collectFlatAddressExpressions,
which causes values with non flat address space put into Postorder and causes
assertion in cloneValueWithNewAddressSpace.

This patch fixes assertion in OpenCL 2.0 conformance test generic_address_space
subtest for amdgcn target.

[arsenm]

LGTM

test/Transforms/InferAddressSpaces/AMDGPU/basic.ll

175

Can you check the full expression? It's on my todo list to search through icmp operands for constant expressions

[yaxunl]

test/Transforms/InferAddressSpaces/AMDGPU/basic.ll

175

will do in commit

lib/Transforms/Scalar/InferAddressSpaces.cpp

InferAddressSpaces::collectFlatAddressExpressions(Function &F) const {
   }
 
   std::vector<WeakTrackingVH> Postorder; // The resultant postorder.
   while (!PostorderStack.empty()) {
     Value *TopVal = PostorderStack.back().first;
     // If the operands of the expression on the top are already explored,
     // adds that expression to the resultant postorder.
     if (PostorderStack.back().second) {
+      if (TopVal->getType()->getPointerAddressSpace() == FlatAddrSpace)
         Postorder.push_back(TopVal);
       PostorderStack.pop_back();
       continue;
     }
     // Otherwise, adds its operands to the stack and explores them.
     PostorderStack.back().second = true;
     for (Value *PtrOperand : getPointerOperands(*TopVal)) {
       appendsFlatAddressExpressionToPostorderStack(PtrOperand, PostorderStack,
                                                    Visited);

test/Transforms/InferAddressSpaces/AMDGPU/basic.ll

 ; CHECK: %cast.cmp = addrspacecast i32 addrspace(3)* %cmp.ptr to i32 addrspace(4)*
 ; CHECK: %ret = cmpxchg i32 addrspace(4)* addrspace(3)* %cas.ptr, i32 addrspace(4)* %cast.cmp, i32 addrspace(4)* %val seq_cst monotonic
 define { i32 addrspace(4)*, i1 } @cmpxchg_group_to_flat_wrong_operand(i32 addrspace(4)* addrspace(3)* %cas.ptr, i32 addrspace(3)* %cmp.ptr, i32 addrspace(4)* %val) #0 {
   %cast.cmp = addrspacecast i32 addrspace(3)* %cmp.ptr to i32 addrspace(4)*
   %ret = cmpxchg i32 addrspace(4)* addrspace(3)* %cas.ptr, i32 addrspace(4)* %cast.cmp, i32 addrspace(4)* %val seq_cst monotonic
   ret { i32 addrspace(4)*, i1 } %ret
 }
 
+; Null pointer in local addr space
+; CHECK-LABEL: @local_nullptr
+; CHECK: addrspacecast (i8* null to i8 addrspace(3)*)
+; CHECK-NOT: i8 addrspace(3)* null
+define void @local_nullptr(i32 addrspace(1)* nocapture %results, i8 addrspace(3)* %a) {
+entry:
+  %tobool = icmp ne i8 addrspace(3)* %a, addrspacecast (i8* null to i8 addrspace(3)*)
+  %conv = zext i1 %tobool to i32
+  store i32 %conv, i32 addrspace(1)* %results, align 4
+  ret void
+}
+
 attributes #0 = { nounwind }