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

Patch Credit to Ankit Jain !!

Differential Revision: http://reviews.llvm.org/D4588

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213662 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index b23a606e08898516aa970970b33f5ee1a11c7a98..431f7323511332cd57bc31953c3e9acd0ae669a7 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2446,6 +2446,12 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
     }
   }
 
+  // (A | B)^(~A) -> (A | ~B)
+  Value *A = nullptr, *B = nullptr;
+  if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
+      match(Op1, m_Not(m_Specific(A))))
+    return BinaryOperator::CreateOr(A, Builder->CreateNot(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/test/Transforms/InstCombine/xor2.ll b/test/Transforms/InstCombine/xor2.ll
index d153e035c8996abc08de1826513672cd5e78a070..e7b1b1bbda8e7e19dc669d7b5c248be3e2838b87 100644 (file)
--- a/test/Transforms/InstCombine/xor2.ll
+++ b/test/Transforms/InstCombine/xor2.ll
@@ -82,3 +82,26 @@ define i32 @test6(i32 %x) {
 ; CHECK: lshr i32 %x, 16
 ; CHECK: ret
 }
+
+
+; (A | B) ^ (~A) -> (A | ~B)
+define i32 @test7(i32 %a, i32 %b) #0 {
+ %or = or i32 %a, %b
+ %neg = xor i32 %a, -1
+ %xor = xor i32 %or, %neg
+ ret i32 %xor
+; CHECK-LABEL: @test7(
+; CHECK-NEXT: %1 = xor i32 %b, -1
+; CHECK-NEXT: %xor = or i32 %a, %1
+}
+
+; (~A) ^ (A | B) -> (A | ~B)
+define i32 @test8(i32 %a, i32 %b) #0 {
+ %neg = xor i32 %a, -1
+ %or = or i32 %a, %b
+ %xor = xor i32 %neg, %or
+ ret i32 %xor
+; CHECK-LABEL: @test8(
+; CHECK-NEXT: %1 = xor i32 %b, -1
+; CHECK-NEXT: %xor = or i32 %a, %1
+}