1 files changed, 29 insertions, 0 deletions
diff --git a/llvm/test/CodeGen/X86/xor-not-combine.ll b/llvm/test/CodeGen/X86/xor-not-combine.ll
new file mode 100644
index 000000000000..af65ade35ce8
--- /dev/null
+++ b/llvm/test/CodeGen/X86/xor-not-combine.ll
@@ -0,0 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+
+; Test for DAG combine: fold (not (sub Y, X)) -> (add X, ~Y)
+; when Y is a constant.
+
+; Test case 1: Y is a constant - should transform to (add X, ~Y)
+define i32 @test_not_sub_constant(i32 %x) {
+; CHECK-LABEL: test_not_sub_constant:
+; CHECK:       # %bb.0:
+; CHECK:         leal -101(%rdi), %eax
+; CHECK-NEXT:    retq
+  %sub = sub i32 100, %x
+  %not = xor i32 %sub, -1
+  ret i32 %not
+}
+
+; Test case 2: Y is not a constant - should NOT optimize
+define i32 @test_not_sub_non_constant(i32 %x, i32 %y) {
+; CHECK-LABEL: test_not_sub_non_constant:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movl %esi, %eax
+; CHECK-NEXT:    subl %edi, %eax
+; CHECK-NEXT:    notl %eax
+; CHECK-NEXT:    retq
+  %sub = sub i32 %y, %x
+  %not = xor i32 %sub, -1
+  ret i32 %not
+}