[PATCH] Added InstCombine transform for pattern "(A ^ B) & ((~A) ^ B) -> False"

[sonam kumari]

Hi David,

Thanks for your valuable comments.I will try to consider general case while doing any optimization in future.
But the patch which you uploaded in rL214342 fails for the following test cases as it doesn't take into consideration the symmetric case. 

The test cases for which it fails are :

define i32 @test15(i32 %x, i32 %y) {
 %nega = xor i32 %x, -1
 %xor = xor i32 %nega, %y
 %xor1 = xor i32 %x, %y
 %and = and i32 %xor, %xor1
 ret i32 %and
}

define i32 @test16(i32 %x, i32 %y) {
 %xor = xor i32 %x, %y
 %nega = xor i32 %x, -1
 %xor1 = xor i32 %nega, %y
 %and = and i32 %xor, %xor1
 ret i32 %and
}

So, I modified the patch and submitting the same.
Kindly review it.

Thanks,
Sonam.

http://reviews.llvm.org/D4690

Files:
  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  test/Transforms/InstCombine/xor2.ll

Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1285,14 +1285,18 @@
       return BinaryOperator::CreateAnd(A, Op0);
 
     // (A ^ B) & ((B ^ C) ^ A) -> (A ^ B) & ~C
-    if (match(Op0, m_Xor(m_Value(A), m_Value(B))))
-      if (match(Op1, m_Xor(m_Xor(m_Specific(B), m_Value(C)), m_Specific(A))))
+    // (B ^ A) & ((B ^ C) ^ A) -> (A ^ B) & ~C
+    if (match(Op1, m_Xor(m_Xor(m_Value(B), m_Value(C)), m_Value(A))))
+      if (match(Op0, m_Xor(m_Specific(A), m_Specific(B))) ||
+          match(Op0, m_Xor(m_Specific(B), m_Specific(A))))
         if (Op1->hasOneUse() || cast<BinaryOperator>(Op1)->hasOneUse())
           return BinaryOperator::CreateAnd(Op0, Builder->CreateNot(C));
 
     // ((A ^ C) ^ B) & (B ^ A) -> (B ^ A) & ~C
+    // ((A ^ C) ^ B) & (A ^ B) -> (B ^ A) & ~C
     if (match(Op0, m_Xor(m_Xor(m_Value(A), m_Value(C)), m_Value(B))))
-      if (match(Op1, m_Xor(m_Specific(B), m_Specific(A))))
+      if (match(Op1, m_Xor(m_Specific(B), m_Specific(A))) ||
+          match(Op1, m_Xor(m_Specific(A), m_Specific(B))))
         if (Op0->hasOneUse() || cast<BinaryOperator>(Op0)->hasOneUse())
           return BinaryOperator::CreateAnd(Op1, Builder->CreateNot(C));
 
Index: test/Transforms/InstCombine/xor2.ll
===================================================================
--- test/Transforms/InstCombine/xor2.ll
+++ test/Transforms/InstCombine/xor2.ll
@@ -167,3 +167,23 @@
 ; CHECK-NEXT: %1 = and i32 %a, %b
 ; CHECK-NEXT: %xor = xor i32 %1, -1
 }
+
+define i32 @test15(i32 %x, i32 %y) {
+ %nega = xor i32 %x, -1
+ %xor = xor i32 %nega, %y
+ %xor1 = xor i32 %x, %y
+ %and = and i32 %xor, %xor1
+ ret i32 %and
+; CHECK-LABEL: @test15(
+; CHECK-NEXT: ret i32 0
+}
+
+define i32 @test16(i32 %x, i32 %y) {
+ %xor = xor i32 %x, %y
+ %nega = xor i32 %x, -1
+ %xor1 = xor i32 %nega, %y
+ %and = and i32 %xor, %xor1
+ ret i32 %and
+; CHECK-LABEL: @test16(
+; CHECK-NEXT: ret i32 0
+}
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