[PATCH] D159510: [InstCombine] Optimize 'xor-and-select' sequence to 'or' for bool

[Qi Hu via Phabricator via llvm-commits]

Qi-Hu created this revision.
Qi-Hu added a reviewer: bryanpkc.
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xor-and-select -> or : https://alive2.llvm.org/ce/z/52ZT62


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159510

Files:
  llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
  llvm/test/Transforms/InstCombine/fold-xor-and-select-i1.ll


Index: llvm/test/Transforms/InstCombine/fold-xor-and-select-i1.ll
===================================================================
--- llvm/test/Transforms/InstCombine/fold-xor-and-select-i1.ll
+++ llvm/test/Transforms/InstCombine/fold-xor-and-select-i1.ll
@@ -4,10 +4,8 @@
 define i1 @max_if(i1 %a, i1 %b) {
 ; CHECK-LABEL: define i1 @max_if
 ; CHECK-SAME: (i1 [[A:%.*]], i1 [[B:%.*]]) {
-; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[B]], true
-; CHECK-NEXT:    [[CMP:%.*]] = and i1 [[TMP1]], [[A]]
-; CHECK-NEXT:    [[TMP2:%.*]] = select i1 [[CMP]], i1 [[A]], i1 [[B]]
-; CHECK-NEXT:    ret i1 [[TMP2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = or i1 [[A]], [[B]]
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %1 = xor i1 %b, true
   %cmp = and i1 %1, %a
Index: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -3174,6 +3174,14 @@
     }
   }
 
+  // select (~b & a), a, b -> or a, b
+  // only for scalar types
+  if (match(CondVal, m_And(m_Not(m_Specific(FalseVal)), m_Specific(TrueVal))) &&
+      TrueVal->getType()->isIntegerTy(1) &&
+      FalseVal->getType()->isIntegerTy(1)) {
+    return BinaryOperator::CreateOr(TrueVal, FalseVal);
+  }
+
   return nullptr;
 }
 


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