[InstSimplify] Add tests for comparison with zero-sized allocs (NFC)

Author: nikic

llvm/test/Transforms/InstSimplify/cmp-alloca-offsets.ll

@@ -230,4 +230,96 @@ define i1 @mixed_alloca_size4() {
   ret i1 %res
 }
 
+define i1 @zst_alloca_start() {
+; CHECK-LABEL: @zst_alloca_start(
+; CHECK-NEXT:    [[A:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    [[A2:%.*]] = alloca {}, align 8
+; CHECK-NEXT:    call void @escape(ptr [[A]], ptr [[A2]])
+; CHECK-NEXT:    ret i1 false
+;
+  %a = alloca i64
+  %a2 = alloca {}
+  %gep = getelementptr i8, ptr %a, i64 0
+  %cmp = icmp eq ptr %gep, %a2
+  call void @escape(ptr %a, ptr %a2)
+  ret i1 %cmp
+}
+
+define i1 @zst_alloca_middle() {
+; CHECK-LABEL: @zst_alloca_middle(
+; CHECK-NEXT:    [[A:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    [[A2:%.*]] = alloca {}, align 8
+; CHECK-NEXT:    call void @escape(ptr [[A]], ptr [[A2]])
+; CHECK-NEXT:    ret i1 false
+;
+  %a = alloca i64
+  %a2 = alloca {}
+  %gep = getelementptr i8, ptr %a, i64 4
+  %cmp = icmp eq ptr %gep, %a2
+  call void @escape(ptr %a, ptr %a2)
+  ret i1 %cmp
+}
+
+define i1 @zst_alloca_end() {
+; CHECK-LABEL: @zst_alloca_end(
+; CHECK-NEXT:    [[A:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    [[A2:%.*]] = alloca {}, align 8
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 8
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[GEP]], [[A2]]
+; CHECK-NEXT:    call void @escape(ptr [[A]], ptr [[A2]])
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %a = alloca i64
+  %a2 = alloca {}
+  %gep = getelementptr i8, ptr %a, i64 8
+  %cmp = icmp eq ptr %gep, %a2
+  call void @escape(ptr %a, ptr %a2)
+  ret i1 %cmp
+}
+
+@gz = external global {}
+
+define i1 @zst_global_start() {
+; CHECK-LABEL: @zst_global_start(
+; CHECK-NEXT:    [[A:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    call void @escape(ptr [[A]], ptr @gz)
+; CHECK-NEXT:    ret i1 false
+;
+  %a = alloca i64
+  %gep = getelementptr i8, ptr %a, i64 0
+  %cmp = icmp eq ptr %gep, @gz
+  call void @escape(ptr %a, ptr @gz)
+  ret i1 %cmp
+}
+
+define i1 @zst_global_middle() {
+; CHECK-LABEL: @zst_global_middle(
+; CHECK-NEXT:    [[A:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    call void @escape(ptr [[A]], ptr @gz)
+; CHECK-NEXT:    ret i1 false
+;
+  %a = alloca i64
+  %gep = getelementptr i8, ptr %a, i64 4
+  %cmp = icmp eq ptr %gep, @gz
+  call void @escape(ptr %a, ptr @gz)
+  ret i1 %cmp
+}
+
+define i1 @zst_global_end() {
+; CHECK-LABEL: @zst_global_end(
+; CHECK-NEXT:    [[A:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 8
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[GEP]], @gz
+; CHECK-NEXT:    call void @escape(ptr [[A]], ptr @gz)
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %a = alloca i64
+  %gep = getelementptr i8, ptr %a, i64 8
+  %cmp = icmp eq ptr %gep, @gz
+  call void @escape(ptr %a, ptr @gz)
+  ret i1 %cmp
+}
+
+declare void @escape(ptr, ptr)
+
 attributes #0 = { null_pointer_is_valid }