[llvm] [AMDGPU][LowerBufferFatPointers] Handle addrspacecast null to p7 (PR #140775)

[Matt Arsenault via llvm-commits]

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@@ -332,6 +332,38 @@ define <2 x ptr addrspace(7)> @addrspacecast_vec(<2 x ptr addrspace(8)> %buf) {
   ret <2 x ptr addrspace(7)> %ret
 }
 
+define ptr addrspace(7) @addrspacecast_null() {
+; CHECK-LABEL: define { ptr addrspace(8), i32 } @addrspacecast_null
+; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-NEXT:    ret { ptr addrspace(8), i32 } zeroinitializer
+;
+  %ret = addrspacecast ptr null to ptr addrspace(7)
+  ret ptr addrspace(7) %ret
+}
+
+define <2 x ptr addrspace(7)> @addrspacecast_null_vec() {
+; CHECK-LABEL: define { <2 x ptr addrspace(8)>, <2 x i32> } @addrspacecast_null_vec
+; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-NEXT:    ret { <2 x ptr addrspace(8)>, <2 x i32> } zeroinitializer
+;
+  %ret = addrspacecast <2 x ptr> zeroinitializer to <2 x ptr addrspace(7)>
+  ret <2 x ptr addrspace(7)> %ret
+}
+
+define i1 @test_null(ptr addrspace(7) %p) {
+; CHECK-LABEL: define i1 @test_null
+; CHECK-SAME: ({ ptr addrspace(8), i32 } [[P:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:    [[P_RSRC:%.*]] = extractvalue { ptr addrspace(8), i32 } [[P]], 0
+; CHECK-NEXT:    [[P_OFF:%.*]] = extractvalue { ptr addrspace(8), i32 } [[P]], 1
+; CHECK-NEXT:    [[IS_NULL_RSRC:%.*]] = icmp eq ptr addrspace(8) [[P_RSRC]], null
+; CHECK-NEXT:    [[IS_NULL_OFF:%.*]] = icmp eq i32 [[P_OFF]], 0
+; CHECK-NEXT:    [[IS_NULL:%.*]] = and i1 [[IS_NULL_RSRC]], [[IS_NULL_OFF]]
+; CHECK-NEXT:    ret i1 [[IS_NULL]]
+;
+  %is.null = icmp eq ptr addrspace(7) %p, addrspacecast (ptr null to ptr addrspace(7))
+  ret i1 %is.null
+}
+
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arsenm wrote:

Also make sure poison and undef work

https://github.com/llvm/llvm-project/pull/140775