This patch implements transform for pattern "(A & ~B) ^ (~A) -> ~(A & B)".

Differential Revision: http://reviews.llvm.org/D4653

llvm-svn: 214479

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 3fd5b7b..9719956 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2524,6 +2524,11 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
       match(Op1, m_Not(m_Specific(A))))
     return BinaryOperator::CreateOr(A, Builder->CreateNot(B));
 
+  // (A & ~B) ^ (~A) -> ~(A & B)
+  if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
+      match(Op1, m_Not(m_Specific(A))))
+    return BinaryOperator::CreateNot(Builder->CreateAnd(A, B));
+
   // (icmp1 A, B) ^ (icmp2 A, B) --> (icmp3 A, B)
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
     if (ICmpInst *LHS = dyn_cast<ICmpInst>(I.getOperand(0)))

diff --git a/llvm/test/Transforms/InstCombine/xor2.ll b/llvm/test/Transforms/InstCombine/xor2.ll
index 6318afe..2f78b29 100644 (file)
--- a/llvm/test/Transforms/InstCombine/xor2.ll
+++ b/llvm/test/Transforms/InstCombine/xor2.ll
@@ -145,3 +145,25 @@ define i32 @test12(i32 %A, i32 %B) {
 ; CHECK-LABEL: @test12(
 ; CHECK-NEXT: ret i32 0
 }
+
+define i32 @test13(i32 %a, i32 %b) {
+ %negb = xor i32 %b, -1
+ %and = and i32 %a, %negb
+ %nega = xor i32 %a, -1
+ %xor = xor i32 %and, %nega
+ ret i32 %xor
+; CHECK-LABEL: @test13(
+; CHECK-NEXT: %1 = and i32 %a, %b
+; CHECK-NEXT: %xor = xor i32 %1, -1
+}
+
+define i32 @test14(i32 %a, i32 %b) {
+ %nega = xor i32 %a, -1
+ %negb = xor i32 %b, -1
+ %and = and i32 %a, %negb
+ %xor = xor i32 %nega, %and
+ ret i32 %xor
+; CHECK-LABEL: @test14(
+; CHECK-NEXT: %1 = and i32 %a, %b
+; CHECK-NEXT: %xor = xor i32 %1, -1
+}