[llvm] 71ef04d - [InstCombine] fold `(icmp eq/ne (or disjoint x, C0), C1)` -> `(icmp eq/ne x, C0^C1)`

[Noah Goldstein via llvm-commits]

Author: Noah Goldstein
Date: 2024-04-09T15:38:18-05:00
New Revision: 71ef04d7cd6c0d6133ab11ca4cfceefe506a1acb

URL: https://github.com/llvm/llvm-project/commit/71ef04d7cd6c0d6133ab11ca4cfceefe506a1acb
DIFF: https://github.com/llvm/llvm-project/commit/71ef04d7cd6c0d6133ab11ca4cfceefe506a1acb.diff

LOG: [InstCombine] fold `(icmp eq/ne (or disjoint x, C0), C1)` -> `(icmp eq/ne x, C0^C1)`

Proof: https://alive2.llvm.org/ce/z/m3xoo_

Closes #87734

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/test/Transforms/InstCombine/icmp-or.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 53aa84d53f3085..9ff1e3aa5502e6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -23,6 +23,7 @@
 #include "llvm/Analysis/VectorUtils.h"
 #include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/PatternMatch.h"
 #include "llvm/Support/KnownBits.h"
@@ -2049,6 +2050,16 @@ Instruction *InstCombinerImpl::foldICmpOrConstant(ICmpInst &Cmp,
   }
 
   Value *OrOp0 = Or->getOperand(0), *OrOp1 = Or->getOperand(1);
+
+  // (icmp eq/ne (or disjoint x, C0), C1)
+  //    -> (icmp eq/ne x, C0^C1)
+  if (Cmp.isEquality() && match(OrOp1, m_ImmConstant()) &&
+      cast<PossiblyDisjointInst>(Or)->isDisjoint()) {
+    Value *NewC =
+        Builder.CreateXor(OrOp1, ConstantInt::get(OrOp1->getType(), C));
+    return new ICmpInst(Pred, OrOp0, NewC);
+  }
+
   const APInt *MaskC;
   if (match(OrOp1, m_APInt(MaskC)) && Cmp.isEquality()) {
     if (*MaskC == C && (C + 1).isPowerOf2()) {

diff  --git a/llvm/test/Transforms/InstCombine/icmp-or.ll b/llvm/test/Transforms/InstCombine/icmp-or.ll
index ce6ebfc1965543..1f9db5e5db9aad 100644
--- a/llvm/test/Transforms/InstCombine/icmp-or.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-or.ll
@@ -955,8 +955,7 @@ 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:    [[TMP1:%.*]] = and i8 [[X:%.*]], -2
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[TMP1]], 18
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[TMP1:%.*]], 18
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %or = or disjoint i8 %x, 1
@@ -967,8 +966,8 @@ 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 [[X:%.*]], 5
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i8 [[OR]], 71
+; CHECK-NEXT:    [[OR:%.*]] = or disjoint i8 [[TMP1:%.*]], 5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i8 [[TMP1]], 66
 ; CHECK-NEXT:    call void @use(i8 [[OR]])
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;