[llvm] [InstCombine] Fold `(icmp eq/ne (xor x, y), C1)` even if multiuse (PR #87275)
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Mon Apr 1 12:09:53 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: None (goldsteinn)
<details>
<summary>Changes</summary>
- **[InstCombine] Add tests for folding `(icmp eq/ne (xor x, C0), C1)`; NFC**
- **[InstCombine] Fold `(icmp eq/ne (xor x, y), C1)` even if multiuse**
---
Full diff: https://github.com/llvm/llvm-project/pull/87275.diff
5 Files Affected:
- (modified) llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp (+7-9)
- (modified) llvm/test/Transforms/InstCombine/icmp-equality-xor.ll (+41-1)
- (modified) llvm/test/Transforms/InstCombine/icmp-or.ll (+3-3)
- (modified) llvm/test/Transforms/InstCombine/prevent-cmp-merge.ll (+7-7)
- (modified) llvm/test/Transforms/InstCombine/select.ll (+2-1)
``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index db302d7e526844..1200f08cef78f1 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3461,15 +3461,13 @@ Instruction *InstCombinerImpl::foldICmpBinOpEqualityWithConstant(
break;
}
case Instruction::Xor:
- if (BO->hasOneUse()) {
- if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
- // For the xor case, we can xor two constants together, eliminating
- // the explicit xor.
- return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
- } else if (C.isZero()) {
- // Replace ((xor A, B) != 0) with (A != B)
- return new ICmpInst(Pred, BOp0, BOp1);
- }
+ if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
+ // For the xor case, we can xor two constants together, eliminating
+ // the explicit xor.
+ return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
+ } else if (C.isZero()) {
+ // Replace ((xor A, B) != 0) with (A != B)
+ return new ICmpInst(Pred, BOp0, BOp1);
}
break;
case Instruction::Or: {
diff --git a/llvm/test/Transforms/InstCombine/icmp-equality-xor.ll b/llvm/test/Transforms/InstCombine/icmp-equality-xor.ll
index f5d5ef32c81e81..e8a78df6d5f756 100644
--- a/llvm/test/Transforms/InstCombine/icmp-equality-xor.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-equality-xor.ll
@@ -88,7 +88,7 @@ define i1 @cmpeq_xor_cst1_commuted(i32 %a, i32 %b) {
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP1]], 10
; CHECK-NEXT: ret i1 [[CMP]]
;
- %b2 = mul i32 %b, %b ; thwart complexity-based canonicalization
+ %b2 = mul i32 %b, %b ; thwart complexity-based canonicalization
%c = xor i32 %a, 10
%cmp = icmp eq i32 %b2, %c
ret i1 %cmp
@@ -145,3 +145,43 @@ entry:
%cmp = icmp ne <2 x i8> %xor, <i8 9, i8 79>
ret <2 x i1> %cmp
}
+
+declare void @use.i8(i8)
+define i1 @fold_xorC_eq0_multiuse(i8 %x, i8 %y) {
+; CHECK-LABEL: @fold_xorC_eq0_multiuse(
+; CHECK-NEXT: [[XX:%.*]] = xor i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X]], [[Y]]
+; CHECK-NEXT: call void @use.i8(i8 [[XX]])
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %xx = xor i8 %x, %y
+ %r = icmp eq i8 %xx, 0
+ call void @use.i8(i8 %xx)
+ ret i1 %r
+}
+
+define i1 @fold_xorC_eq1_multiuse_fail(i8 %x, i8 %y) {
+; CHECK-LABEL: @fold_xorC_eq1_multiuse_fail(
+; CHECK-NEXT: [[XX:%.*]] = xor i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[XX]], 1
+; CHECK-NEXT: call void @use.i8(i8 [[XX]])
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %xx = xor i8 %x, %y
+ %r = icmp eq i8 %xx, 1
+ call void @use.i8(i8 %xx)
+ ret i1 %r
+}
+
+define i1 @fold_xorC_neC_multiuse(i8 %x) {
+; CHECK-LABEL: @fold_xorC_neC_multiuse(
+; CHECK-NEXT: [[XX:%.*]] = xor i8 [[X:%.*]], 45
+; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[X]], 110
+; CHECK-NEXT: call void @use.i8(i8 [[XX]])
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %xx = xor i8 %x, 45
+ %r = icmp ne i8 %xx, 67
+ call void @use.i8(i8 %xx)
+ ret i1 %r
+}
diff --git a/llvm/test/Transforms/InstCombine/icmp-or.ll b/llvm/test/Transforms/InstCombine/icmp-or.ll
index 922845c1e7e2d8..dce8b6a3b282e6 100644
--- a/llvm/test/Transforms/InstCombine/icmp-or.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-or.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+; RUN: opt < %s -passes='instcombine<no-verify-fixpoint>' -S | FileCheck %s
declare void @use(i8)
@@ -434,7 +434,7 @@ define i1 @icmp_or_xor_2_3_fail(i64 %x1, i64 %y1, i64 %x2, i64 %y2) {
; CHECK-NEXT: [[XOR1:%.*]] = xor i64 [[X2:%.*]], [[Y2:%.*]]
; CHECK-NEXT: [[OR:%.*]] = or i64 [[XOR]], [[XOR1]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[OR]], 0
-; CHECK-NEXT: [[CMP_1:%.*]] = icmp eq i64 [[XOR]], 0
+; CHECK-NEXT: [[CMP_1:%.*]] = icmp eq i64 [[X1]], [[Y1]]
; CHECK-NEXT: [[OR1:%.*]] = or i1 [[CMP]], [[CMP_1]]
; CHECK-NEXT: ret i1 [[OR1]]
;
@@ -455,7 +455,7 @@ define i1 @icmp_or_xor_2_4_fail(i64 %x1, i64 %y1, i64 %x2, i64 %y2) {
; CHECK-NEXT: [[XOR1:%.*]] = xor i64 [[X2:%.*]], [[Y2:%.*]]
; CHECK-NEXT: [[OR:%.*]] = or i64 [[XOR]], [[XOR1]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[OR]], 0
-; CHECK-NEXT: [[CMP_1:%.*]] = icmp eq i64 [[XOR1]], 0
+; CHECK-NEXT: [[CMP_1:%.*]] = icmp eq i64 [[X2]], [[Y2]]
; CHECK-NEXT: [[OR1:%.*]] = or i1 [[CMP]], [[CMP_1]]
; CHECK-NEXT: ret i1 [[OR1]]
;
diff --git a/llvm/test/Transforms/InstCombine/prevent-cmp-merge.ll b/llvm/test/Transforms/InstCombine/prevent-cmp-merge.ll
index cd05022b0d35da..e5906e7a969730 100644
--- a/llvm/test/Transforms/InstCombine/prevent-cmp-merge.ll
+++ b/llvm/test/Transforms/InstCombine/prevent-cmp-merge.ll
@@ -7,9 +7,9 @@
define zeroext i1 @test1(i32 %lhs, i32 %rhs) {
; CHECK-LABEL: @test1(
-; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[LHS:%.*]], 5
-; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[XOR]], 10
-; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[XOR]], [[RHS:%.*]]
+; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[LHS:%.*]], 15
+; CHECK-NEXT: [[TMP1:%.*]] = xor i32 [[LHS]], [[RHS:%.*]]
+; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[TMP1]], 5
; CHECK-NEXT: [[SEL:%.*]] = or i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: ret i1 [[SEL]]
;
@@ -23,9 +23,9 @@ define zeroext i1 @test1(i32 %lhs, i32 %rhs) {
define zeroext i1 @test1_logical(i32 %lhs, i32 %rhs) {
; CHECK-LABEL: @test1_logical(
-; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[LHS:%.*]], 5
-; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[XOR]], 10
-; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[XOR]], [[RHS:%.*]]
+; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[LHS:%.*]], 15
+; CHECK-NEXT: [[TMP1:%.*]] = xor i32 [[LHS]], [[RHS:%.*]]
+; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[TMP1]], 5
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i1 true, i1 [[CMP2]]
; CHECK-NEXT: ret i1 [[SEL]]
;
@@ -40,7 +40,7 @@ define zeroext i1 @test1_logical(i32 %lhs, i32 %rhs) {
define zeroext i1 @test2(i32 %lhs, i32 %rhs) {
; CHECK-LABEL: @test2(
; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[LHS:%.*]], [[RHS:%.*]]
-; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[XOR]], 0
+; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[LHS]], [[RHS]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[XOR]], 32
; CHECK-NEXT: [[SEL:%.*]] = xor i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: ret i1 [[SEL]]
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index 278cabdff9ed3e..30bbc86b091494 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -3698,7 +3698,8 @@ exit:
define i32 @src_select_xxory_eq0_xorxy_y(i32 %x, i32 %y) {
; CHECK-LABEL: @src_select_xxory_eq0_xorxy_y(
; CHECK-NEXT: [[XOR0:%.*]] = icmp eq i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[COND:%.*]] = select i1 [[XOR0]], i32 0, i32 [[Y]]
+; CHECK-NEXT: [[XOR:%.*]] = select i1 [[XOR0]], i32 [[X]], i32 0
+; CHECK-NEXT: [[COND:%.*]] = xor i32 [[XOR]], [[Y]]
; CHECK-NEXT: ret i32 [[COND]]
;
%xor = xor i32 %x, %y
``````````
</details>
https://github.com/llvm/llvm-project/pull/87275
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