[PATCH] Added InstCombine Transform for pattern "((~A & B) | A) -> (A | B)"

[Duncan P. N. Exon Smith]

> On 2014-Jul-18, at 12:59, suyog <suyog.sarda at samsung.com> wrote:
> 
> Hi nicholas, rafael, dexonsmith,
> 
> This patch implements transform for pattern "((~A & B) | A) -> (A | B)"
> 
> Please help in reviewing this patch.
> 
> http://reviews.llvm.org/D4591
> 
> Files:
>  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
>  test/Transforms/InstCombine/or.ll
> 

This looks good, but I think you should handle this (essentially
equivalent) transformation as well:

    ((A & B) | ~A) -> (~A | B)

I'm not sure if there's a way to share logic, but it would be great if
there is.

> Index: test/Transforms/InstCombine/or.ll
> ===================================================================
> --- test/Transforms/InstCombine/or.ll
> +++ test/Transforms/InstCombine/or.ll
> @@ -408,3 +408,12 @@
>   %or = or i32 %x, %sext
>   ret i32 %or
> }
> +
> +define i32 @test39(i32 %a, i32 %b) {
> +; CHECK-LABEL: test39(
> +; CHECK-NEXT: %or = or i32 %a, %b
> +  %xor = xor i32 %a, -1
> +  %and = and i32 %xor, %b
> +  %or = or i32 %and, %a
> +  ret i32 %or
> +}
> Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
> ===================================================================
> --- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
> +++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
> @@ -1988,6 +1988,11 @@
>     return BinaryOperator::CreateXor(NOr, C1);
>   }
> 
> +  // ((~A & B) | A) -> (A | B)
> +  if (match(Op0, m_And(m_Not(m_Value(A)), m_Value(B))) &&
> +      match(Op1, m_Specific(A)))
> +    return BinaryOperator::CreateOr(A, B);
> +
>   // (A & C)|(B & D)
>   Value *C = nullptr, *D = nullptr;
>   if (match(Op0, m_And(m_Value(A), m_Value(C))) &&
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