Added InstCombine transform for pattern "(A | B) & ((~A) ^ B) -> (A & B)"

[suyog]

Summary

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

Please help in reviewing the same.

Z3 link : http://rise4fun.com/Z3/4TE2

Thanks,
Suyog

[suyog]

Gentle Ping !!

Patch won't take much time to review :)

[majnemer]

LGTM

[suyog]

Closed by commit rL214478 (authored by @suyog).

llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

if (match(Op0, m_Xor(m_Value(A), m_Value(B))))
         if (Op1->hasOneUse() || cast<BinaryOperator>(Op1)->hasOneUse())
           return BinaryOperator::CreateAnd(Op0, Builder->CreateNot(C));
 
     // ((A ^ C) ^ B) & (B ^ A) -> (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 (Op0->hasOneUse() || cast<BinaryOperator>(Op0)->hasOneUse())
           return BinaryOperator::CreateAnd(Op1, Builder->CreateNot(C));
+
+    // (A | B) & ((~A) ^ B) -> (A & B)
+    if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
+        match(Op1, m_Xor(m_Not(m_Specific(A)), m_Specific(B))))
+      return BinaryOperator::CreateAnd(A, B);
+
+    // ((~A) ^ B) & (A | B) -> (A & B)
+    if (match(Op0, m_Xor(m_Not(m_Value(A)), m_Value(B))) &&
+        match(Op1, m_Or(m_Specific(A), m_Specific(B))))
+      return BinaryOperator::CreateAnd(A, B);
   }
 
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(Op1))
     if (ICmpInst *LHS = dyn_cast<ICmpInst>(Op0))
       if (Value *Res = FoldAndOfICmps(LHS, RHS))
         return ReplaceInstUsesWith(I, Res);
 
   // If and'ing two fcmp, try combine them into one.

llvm/trunk/test/Transforms/InstCombine/or-xor.ll

define i32 @test11(i32 %A, i32 %B) {
   %xor1 = xor i32 %B, %A
   %not = xor i32 %A, -1
   %xor2 = xor i32 %not, %B
   %or = or i32 %xor1, %xor2
   ret i32 %or
 ; CHECK-LABEL: @test11(
 ; CHECK-NEXT: ret i32 -1
 }
+
+; (x | y) & ((~x) ^ y) -> (x & y)
+define i32 @test12(i32 %x, i32 %y) {
+ %or = or i32 %x, %y
+ %neg = xor i32 %x, -1
+ %xor = xor i32 %neg, %y
+ %and = and i32 %or, %xor
+ ret i32 %and
+; CHECK-LABEL: @test12(
+; CHECK-NEXT: %and = and i32 %x, %y
+; CHECK-NEXT: ret i32 %and
+}
+
+; ((~x) ^ y) & (x | y) -> (x & y)
+define i32 @test13(i32 %x, i32 %y) {
+ %neg = xor i32 %x, -1
+ %xor = xor i32 %neg, %y
+ %or = or i32 %x, %y
+ %and = and i32 %xor, %or
+ ret i32 %and
+; CHECK-LABEL: @test13(
+; CHECK-NEXT: %and = and i32 %x, %y
+; CHECK-NEXT: ret i32 %and
+}