[PATCH] D150750: [Instsimplfy] X == Y ? 0 : X ^ Y --> X ^ Y
Allen zhong via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed May 17 02:38:52 PDT 2023
Allen updated this revision to Diff 522971.
Allen added a comment.
add a negative test select_xor_cmp_unmatched_operands
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D150750/new/
https://reviews.llvm.org/D150750
Files:
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/test/Transforms/InstSimplify/select.ll
Index: llvm/test/Transforms/InstSimplify/select.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/select.ll
+++ llvm/test/Transforms/InstSimplify/select.ll
@@ -1496,3 +1496,62 @@
%5 = select i1 %3, i8 42, i8 %4
ret i8 %5
}
+
+; X == Y ? 0 : X ^ Y --> X ^ Y, https://alive2.llvm.org/ce/z/cykffE
+define i8 @select_xor_cmp(i8 %0, i8 %1) {
+; CHECK-LABEL: @select_xor_cmp(
+; CHECK-NEXT: [[TMP3:%.*]] = xor i8 [[TMP1:%.*]], [[TMP0:%.*]]
+; CHECK-NEXT: ret i8 [[TMP3]]
+;
+ %3 = icmp eq i8 %1, %0
+ %4 = xor i8 %1, %0
+ %5 = select i1 %3, i8 0, i8 %4
+ ret i8 %5
+}
+
+define <2 x i8> @select_xor_cmp_vec(<2 x i8> %0, <2 x i8> %1) {
+; CHECK-LABEL: @select_xor_cmp_vec(
+; CHECK-NEXT: [[TMP3:%.*]] = xor <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]]
+; CHECK-NEXT: ret <2 x i8> [[TMP3]]
+;
+ %3 = icmp eq <2 x i8> %1, %0
+ %4 = xor <2 x i8> %1, %0
+ %5 = select <2 x i1> %3, <2 x i8> <i8 0, i8 0>, <2 x i8> %4
+ ret <2 x i8> %5
+}
+
+define i8 @select_xor_cmp_swap(i8 %0, i8 %1) {
+; CHECK-LABEL: @select_xor_cmp_swap(
+; CHECK-NEXT: [[TMP3:%.*]] = xor i8 [[TMP0:%.*]], [[TMP1:%.*]]
+; CHECK-NEXT: ret i8 [[TMP3]]
+;
+ %3 = icmp eq i8 %1, %0
+ %4 = xor i8 %0, %1
+ %5 = select i1 %3, i8 0, i8 %4
+ ret i8 %5
+}
+
+define <2 x i8> @select_xor_cmp_vec_swap(<2 x i8> %0, <2 x i8> %1) {
+; CHECK-LABEL: @select_xor_cmp_vec_swap(
+; CHECK-NEXT: [[TMP3:%.*]] = xor <2 x i8> [[TMP0:%.*]], [[TMP1:%.*]]
+; CHECK-NEXT: ret <2 x i8> [[TMP3]]
+;
+ %3 = icmp eq <2 x i8> %1, %0
+ %4 = xor <2 x i8> %0, %1
+ %5 = select <2 x i1> %3, <2 x i8> <i8 0, i8 0>, <2 x i8> %4
+ ret <2 x i8> %5
+}
+
+; Negative test: the xor operands are not %0 and %1
+define i8 @select_xor_cmp_unmatched_operands(i8 %0, i8 %1, i8 %c) {
+; CHECK-LABEL: @select_xor_cmp_unmatched_operands(
+; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i8 [[TMP1:%.*]], [[TMP0:%.*]]
+; CHECK-NEXT: [[TMP4:%.*]] = xor i8 [[TMP1]], [[C:%.*]]
+; CHECK-NEXT: [[TMP5:%.*]] = select i1 [[TMP3]], i8 0, i8 [[TMP4]]
+; CHECK-NEXT: ret i8 [[TMP5]]
+;
+ %3 = icmp eq i8 %1, %0
+ %4 = xor i8 %1, %c
+ %5 = select i1 %3, i8 0, i8 %4
+ ret i8 %5
+}
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4256,9 +4256,11 @@
NewOps[0] == NewOps[1])
return NewOps[0];
- // x - x -> 0. This is non-refining, because x is non-poison by assumption
- // and this case never wraps, so nowrap flags can be ignored.
- if (Opcode == Instruction::Sub && NewOps[0] == NewOps[1]) {
+ // x - x -> 0, x ^ x -> 0. This is non-refining, because x is non-poison
+ // by assumption and this case never wraps, so nowrap flags can be
+ // ignored.
+ if ((Opcode == Instruction::Sub || Opcode == Instruction::Xor) &&
+ NewOps[0] == NewOps[1]) {
assert(NewOps[0] == RepOp && "Precondition for non-poison assumption");
return Constant::getNullValue(I->getType());
}
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