[PATCH] Transform OR of SELECTs to SELECT of ORs

[Hal Finkel]

----- Original Message -----
> From: "Muhammad Tauqir" <muhammadtauqir16 at gmail.com>
> To: muhammadtauqir16 at gmail.com
> Cc: llvm-commits at cs.uiuc.edu
> Sent: Friday, February 1, 2013 7:59:28 AM
> Subject: [PATCH] Transform OR of SELECTs to SELECT of ORs
> 
> More descriptively, the transform is:
> (or (bool?A:B),(bool?C:D)) --> (bool?(or A,C):(or B,D))
> 
> By the time the OR is visited, both the SELECTs have been visited and
> not optimized and the OR itself hasn't been transformed so we do
> this transform in the hopes that the new ORs will be optimized.
> 
> The transform is explicitly disabled for vector-selects until
> "codegen matures to handle them better".

Can you be more specific about what needs to be improved, and on what targets?

Thanks again,
Hal

> 
> http://llvm-reviews.chandlerc.com/D362
> 
> Files:
>   lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
>   test/Transforms/InstCombine/logical-select.ll
> 
> Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
> ===================================================================
> --- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
> +++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
> @@ -2071,6 +2071,22 @@
>      return BinaryOperator::CreateOr(Inner, C1);
>    }
>  
> +  // Change (or (bool?A:B),(bool?C:D)) --> (bool?(or A,C):(or B,D))
> +  // Since this OR statement hasn't been optimized further yet, we
> hope
> +  // that this transformation will allow the new ORs to be
> optimized.
> +  {
> +    Value *X = 0;
> +    // FIXME: Disable vector-select until codegen matures to handle
> them better.
> +    // See test32 in test/Transforms/InstCombine/or.ll
> +    if (!I.getType()->isVectorTy())
> +      if (match(Op0, m_Select(m_Value(X), m_Value(A), m_Value(B)))
> &&
> +          match(Op1, m_Select(m_Value(X), m_Value(C), m_Value(D))))
> {
> +        Value *orTrue = Builder->CreateOr(A, C);
> +        Value *orFalse = Builder->CreateOr(B, D);
> +        return SelectInst::Create(X, orTrue, orFalse);
> +      }
> +  }
> +
>    return Changed ? &I : 0;
>  }
>  
> Index: test/Transforms/InstCombine/logical-select.ll
> ===================================================================
> --- test/Transforms/InstCombine/logical-select.ll
> +++ test/Transforms/InstCombine/logical-select.ll
> @@ -10,10 +10,8 @@
>    %j = or i32 %g, %i
>    ret i32 %j
>  ; CHECK: %e = icmp slt i32 %a, %b
> -; CHECK-NEXT: %g = select i1 %e, i32 %c, i32 0
> -; CHECK-NEXT: %i = select i1 %e, i32 0, i32 %d
> -; CHECK-NEXT: %j = or i32 %g, %i
> -; CHECK-NEXT: ret i32 %j
> +; CHECK-NEXT: [[result:%.*]] = select i1 %e, i32 %c, i32 %d
> +; CHECK-NEXT: ret i32 [[result]]
>  }
>  define i32 @bar(i32 %a, i32 %b, i32 %c, i32 %d) nounwind {
>    %e = icmp slt i32 %a, %b
> @@ -24,10 +22,8 @@
>    %j = or i32 %i, %g
>    ret i32 %j
>  ; CHECK: %e = icmp slt i32 %a, %b
> -; CHECK-NEXT: %g = select i1 %e, i32 %c, i32 0
> -; CHECK-NEXT: %i = select i1 %e, i32 0, i32 %d
> -; CHECK-NEXT: %j = or i32 %i, %g
> -; CHECK-NEXT: ret i32 %j
> +; CHECK-NEXT: [[result:%.*]] = select i1 %e, i32 %c, i32 %d
> +; CHECK-NEXT: ret i32 [[result]]
>  }
>  
>  define i32 @goo(i32 %a, i32 %b, i32 %c, i32 %d) nounwind {
> @@ -40,10 +36,8 @@
>    %3 = or i32 %1, %2
>    ret i32 %3
>  ; CHECK: %0 = icmp slt i32 %a, %b
> -; CHECK-NEXT: %1 = select i1 %0, i32 %c, i32 0
> -; CHECK-NEXT: %2 = select i1 %0, i32 0, i32 %d
> -; CHECK-NEXT: %3 = or i32 %1, %2
> -; CHECK-NEXT: ret i32 %3
> +; CHECK-NEXT: [[result:%.*]] = select i1 %0, i32 %c, i32 %d
> +; CHECK-NEXT: ret i32 [[result]]
>  }
>  define i32 @poo(i32 %a, i32 %b, i32 %c, i32 %d) nounwind {
>  entry:
> @@ -55,10 +49,8 @@
>    %3 = or i32 %1, %2
>    ret i32 %3
>  ; CHECK: %0 = icmp slt i32 %a, %b
> -; CHECK-NEXT: %1 = select i1 %0, i32 %c, i32 0
> -; CHECK-NEXT: %2 = select i1 %0, i32 0, i32 %d
> -; CHECK-NEXT: %3 = or i32 %1, %2
> -; CHECK-NEXT: ret i32 %3
> +; CHECK-NEXT: [[result:%.*]] = select i1 %0, i32 %c, i32 %d
> +; CHECK-NEXT: ret i32 [[result]]
>  }
>  
>  define i32 @par(i32 %a, i32 %b, i32 %c, i32 %d) nounwind {
> @@ -71,8 +63,6 @@
>    %3 = or i32 %1, %2
>    ret i32 %3
>  ; CHECK: %0 = icmp slt i32 %a, %b
> -; CHECK-NEXT: %1 = select i1 %0, i32 %c, i32 0
> -; CHECK-NEXT: %2 = select i1 %0, i32 0, i32 %d
> -; CHECK-NEXT: %3 = or i32 %1, %2
> -; CHECK-NEXT: ret i32 %3
> +; CHECK-NEXT: [[result:%.*]] = select i1 %0, i32 %c, i32 %d
> +; CHECK-NEXT: ret i32 [[result]]
>  }
> 
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