[InstCombine] Fold (icmp eq/ne (xor x, y), C1) even if multiuse

goldsteinn · goldsteinn · commit 166c1849d6da · 2024-06-07T15:06:41.000-05:00
Two folds unlocked: `(icmp eq/ne (xor x, C0), C1)` -> `(icmp eq/ne x, C2)` `(icmp eq/ne (xor x, y), 0)` -> `(icmp eq/ne x, y)` This fixes regressions assosiated with #87180 Closes #87275
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3502,15 +3502,13 @@ 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
@@ -150,7 +150,7 @@ 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 [[XX]], 0
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[X]], [[Y]]
 ; CHECK-NEXT:    call void @use.i8(i8 [[XX]])
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
@@ -176,7 +176,7 @@ define i1 @fold_xorC_eq1_multiuse_fail(i8 %x, i8 %y) {
 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 [[XX]], 67
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[X]], 110
 ; CHECK-NEXT:    call void @use.i8(i8 [[XX]])
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
diff --git 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)
 
@@ -428,13 +428,17 @@ define i1 @icmp_or_xor_2_ne_fail(i64 %x1, i64 %y1, i64 %x2, i64 %y2) {
 
 ; negative test - xor multiuse
 
+; NB: This requires more than 1 iteration to simplify. After we
+; simplify `%cmp_1 = icmp eq i64 %xor, 0`, `%xor = xor i64 %x1, %y1`
+; has one use which allows for complete simplification (rooted on
+; `%or1 = or i1 %cmp, %cmp_1` so we don't end up adding it back).
 define i1 @icmp_or_xor_2_3_fail(i64 %x1, i64 %y1, i64 %x2, i64 %y2) {
 ; CHECK-LABEL: @icmp_or_xor_2_3_fail(
 ; CHECK-NEXT:    [[XOR:%.*]] = xor i64 [[X1:%.*]], [[Y1:%.*]]
 ; 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 +459,7 @@ 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]]
 ;
@@ -955,7 +959,7 @@ define i1 @icmp_or_xor_with_sub_3_6(i64 %x1, i64 %y1, i64 %x2, i64 %y2, i64 %x3,
 
 define i1 @or_disjoint_with_constants(i8 %x) {
 ; CHECK-LABEL: @or_disjoint_with_constants(
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[TMP1:%.*]], 18
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[X:%.*]], 18
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %or = or disjoint i8 %x, 1
@@ -966,8 +970,8 @@ define i1 @or_disjoint_with_constants(i8 %x) {
 
 define i1 @or_disjoint_with_constants2(i8 %x) {
 ; CHECK-LABEL: @or_disjoint_with_constants2(
-; CHECK-NEXT:    [[OR:%.*]] = or disjoint i8 [[TMP1:%.*]], 5
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i8 [[TMP1]], 66
+; CHECK-NEXT:    [[OR:%.*]] = or disjoint i8 [[X:%.*]], 5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i8 [[X]], 66
 ; CHECK-NEXT:    call void @use(i8 [[OR]])
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
diff --git 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
@@ -4547,7 +4547,7 @@ define i32 @src_no_trans_select_xor_eq0_xor_or(i32 %x, i32 %y) {
 define i32 @src_no_trans_select_xor_eq0_and_xor(i32 %x, i32 %y) {
 ; CHECK-LABEL: @src_no_trans_select_xor_eq0_and_xor(
 ; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[XOR0:%.*]] = icmp eq i32 [[XOR]], 0
+; CHECK-NEXT:    [[XOR0:%.*]] = icmp eq i32 [[X]], [[Y]]
 ; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X]], [[Y]]
 ; CHECK-NEXT:    [[COND:%.*]] = select i1 [[XOR0]], i32 [[AND]], i32 [[XOR]]
 ; CHECK-NEXT:    ret i32 [[COND]]
@@ -4563,7 +4563,7 @@ define i32 @src_no_trans_select_xor_eq0_and_xor(i32 %x, i32 %y) {
 define i32 @src_no_trans_select_xor_eq0_or_xor(i32 %x, i32 %y) {
 ; CHECK-LABEL: @src_no_trans_select_xor_eq0_or_xor(
 ; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[XOR0:%.*]] = icmp eq i32 [[XOR]], 0
+; CHECK-NEXT:    [[XOR0:%.*]] = icmp eq i32 [[X]], [[Y]]
 ; CHECK-NEXT:    [[OR:%.*]] = or i32 [[X]], [[Y]]
 ; CHECK-NEXT:    [[COND:%.*]] = select i1 [[XOR0]], i32 [[OR]], i32 [[XOR]]
 ; CHECK-NEXT:    ret i32 [[COND]]
