[PATCH] InstCombine ((A | ~B) ^ (~A | B)) to A ^ B

[Mayur Pandey]

Hi majnemer,

Hi,
A patch in instcombine to transform  ((A | ~B) ^ (~A | B)) -> A ^ B.
Please review the patch.

Proof
$ cat t.cvc
A, B : BITVECTOR(32);
QUERY BVXOR((A | ~B),(~A |B)) = BVXOR(A,B);
$ cvc3 t.cvc 
Valid.

http://reviews.llvm.org/D4883

Files:
  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  test/Transforms/InstCombine/or-xor.ll

Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2508,6 +2508,34 @@
       if ((A == C && B == D) || (A == D && B == C))
         return BinaryOperator::CreateXor(A, B);
     }
+    // (A | ~B) ^ (~A | B) -> A ^ B
+    // (A | ~B) ^ (B | ~A) -> A ^ B
+    if (match(Op0I, m_Or(m_Value(A), m_Not(m_Value(B)))) &&
+        (match(Op1I, m_Or(m_Not(m_Specific(A)), m_Specific(B))) ||
+         match(Op1I, m_Or(m_Specific(B), m_Not(m_Specific(A)))))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
+    // (~B | A) ^ (~A | B) -> A ^ B
+    // (~B | A) ^ (B | ~A) -> A ^ B
+    if (match(Op0I, m_Or(m_Not(m_Value(B)), m_Value(A))) &&
+        (match(Op1I, m_Or(m_Not(m_Specific(A)), m_Specific(B))) ||
+         match(Op1I, m_Or(m_Specific(B), m_Not(m_Specific(A)))))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
+    // (~A | B) ^ (A | ~B) -> A ^ B
+    // (~A | B) ^ (~B | A) -> A ^ B
+    if (match(Op0I, m_Or(m_Not(m_Value(A)), m_Value(B))) &&
+        (match(Op1I, m_Or(m_Specific(A), m_Not(m_Specific(B)))) ||
+         match(Op1I, m_Or(m_Not(m_Specific(B)), m_Specific(A))))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
+    // (B | ~A) ^ (A | ~B) -> A ^ B
+    // (B | ~A) ^ (~B | A) -> A ^ B
+    if (match(Op0I, m_Or(m_Value(B), m_Not(m_Value(A)))) &&
+        (match(Op1I, m_Or(m_Specific(A), m_Not(m_Specific(B)))) ||
+         match(Op1I, m_Or(m_Not(m_Specific(B)), m_Specific(A))))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
     // (A ^ B)^(A | B) -> A & B
     if (match(Op0I, m_Xor(m_Value(A), m_Value(B))) &&
         match(Op1I, m_Or(m_Value(C), m_Value(D)))) {
Index: test/Transforms/InstCombine/or-xor.ll
===================================================================
--- test/Transforms/InstCombine/or-xor.ll
+++ test/Transforms/InstCombine/or-xor.ll
@@ -147,3 +147,16 @@
 ; CHECK-NEXT: %1 = and i32 %y, %x
 ; CHECK-NEXT: ret i32 %1
 }
+
+; ((x | ~y) ^ (~x | y)) -> x ^ y
+define i32 @test16(i32 %x, i32 %y) {
+  %1 = xor i32 %y, -1
+  %2 = xor i32 %x, -1
+  %3 = or i32 %x, %1
+  %4 = or i32 %2, %y
+  %5 = xor i32 %3, %4
+  ret i32 %5
+; CHECK-LABEL: @test16(
+; CHECK-NEXT: %1 = xor i32 %x, %y
+; CHECK-NEXT: ret i32 %1
+}
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