[PATCH] Instcombine ( ( ~A ^ B ) ^ ( A & ~B ) ) to A | ~B

[Karthik Bhat]

Hi majnemer,

Hi David,
Another small patch in instcombine to transform ( ( ~A ^ B ) ^ ( A & ~B ) ) to A | ~B .
Please if you could let me know your i/p's on the same.

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

$ cvc3 t.cvc
Valid.

Thanks
Karthik Bhat

http://reviews.llvm.org/D4878

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
@@ -2528,6 +2528,31 @@
     if (match(Op0I, m_Xor(m_Value(A), m_Value(B))) &&
         match(Op1I, m_And(m_Specific(A), m_Specific(B))))
       return BinaryOperator::CreateOr(A, B);
+
+    // (~A ^ B) ^ (A & ~B) -> (A | ~B)
+    // (~A ^ B) ^ (~B & A) -> (A | ~B)
+    if (match(Op0I, m_Xor(m_Not(m_Value(A)), m_Value(B))) &&
+        (match(Op1I, m_And(m_Specific(A), m_Not(m_Specific(B)))) ||
+         match(Op1I, m_And(m_Not(m_Specific(B)), m_Specific(A)))))
+      return BinaryOperator::CreateOr(A, Builder->CreateNot(B));
+    // (B ^ ~A) ^ (A & ~B) -> (A | ~B)
+    // (B ^ ~A) ^ (~B & A) -> (A | ~B)
+    if (match(Op0I, m_Xor(m_Value(B), m_Not(m_Value(A)))) &&
+        (match(Op1I, m_And(m_Specific(A), m_Not(m_Specific(B)))) ||
+         match(Op1I, m_And(m_Not(m_Specific(B)), m_Specific(A)))))
+      return BinaryOperator::CreateOr(A, Builder->CreateNot(B));
+    // (A & ~B) ^ (B ^ ~A) -> (A | ~B)
+    // (A & ~B) ^ (~A ^ B) -> (A | ~B)
+    if (match(Op0I, m_And(m_Value(A), m_Not(m_Value(B)))) &&
+        (match(Op1I, m_Xor(m_Specific(B), m_Not(m_Specific(A)))) ||
+         match(Op1I, m_Xor(m_Not(m_Specific(A)), m_Specific(B)))))
+      return BinaryOperator::CreateOr(A, Builder->CreateNot(B));
+    // (~B & A) ^ (B ^ ~A) -> (A | ~B)
+    // (~B & A) ^ (~A ^ B) -> (A | ~B)
+    if (match(Op0I, m_And(m_Not(m_Value(B)), m_Value(A))) &&
+        (match(Op1I, m_Xor(m_Specific(B), m_Not(m_Specific(A)))) ||
+         match(Op1I, m_Xor(m_Not(m_Specific(A)), m_Specific(B)))))
+      return BinaryOperator::CreateOr(A, Builder->CreateNot(B));
   }
 
   // (A | B)^(~A) -> (A | ~B)
Index: test/Transforms/InstCombine/or-xor.ll
===================================================================
--- test/Transforms/InstCombine/or-xor.ll
+++ test/Transforms/InstCombine/or-xor.ll
@@ -147,3 +147,17 @@
 ; 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 %x, -1
+  %2 = xor i32 %1, %y
+  %3 = xor i32 %y, -1
+  %4 = and i32 %3, %x
+  %5 = xor i32 %2, %4
+  ret i32 %5
+; CHECK-LABEL: @test16(
+; CHECK-NEXT: %1 = xor i32 %y, -1
+; CHECK-NEXT: %2 = or i32 %x, %1
+; CHECK-NEXT: ret i32 %2
+}
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