[llvm-commits] [llvm] r158237 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineAddSub.cpp test/Transforms/InstCombine/pr12338.ll

[Evan Cheng]

Is this really right? I thought LLVM passes like to canonicalize expressions so the immediate is always the RHS.

Evan

On Jun 8, 2012, at 3:30 PM, Nuno Lopes wrote:

> Author: nlopes
> Date: Fri Jun  8 17:30:05 2012
> New Revision: 158237
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=158237&view=rev
> Log:
> canonicalize:
> -%a + 42
> into
> 42 - %a
> 
> previously we were emitting:
> -(%a + 42)
> 
> This fixes the infinite loop in PR12338. The generated code is still not perfect, though.
> Will work on that next
> 
> Added:
>    llvm/trunk/test/Transforms/InstCombine/pr12338.ll
> Modified:
>    llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
> 
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=158237&r1=158236&r2=158237&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp Fri Jun  8 17:30:05 2012
> @@ -170,10 +170,11 @@
>   // -A + B  -->  B - A
>   // -A + -B  -->  -(A + B)
>   if (Value *LHSV = dyn_castNegVal(LHS)) {
> -    if (Value *RHSV = dyn_castNegVal(RHS)) {
> -      Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
> -      return BinaryOperator::CreateNeg(NewAdd);
> -    }
> +    if (!isa<Constant>(RHS))
> +      if (Value *RHSV = dyn_castNegVal(RHS)) {
> +        Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
> +        return BinaryOperator::CreateNeg(NewAdd);
> +      }
> 
>     return BinaryOperator::CreateSub(RHS, LHSV);
>   }
> 
> Added: llvm/trunk/test/Transforms/InstCombine/pr12338.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/pr12338.ll?rev=158237&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/pr12338.ll (added)
> +++ llvm/trunk/test/Transforms/InstCombine/pr12338.ll Fri Jun  8 17:30:05 2012
> @@ -0,0 +1,24 @@
> +; RUN: opt < %s -instcombine -S | FileCheck %s
> +
> +define void @entry() nounwind {
> +entry:
> +  br label %for.cond
> +
> +for.cond:
> +  %local = phi <1 x i32> [ <i32 0>, %entry ], [ %phi2, %cond.end47 ]
> +; CHECK: sub <1 x i32> <i32 92>, %local
> +  %phi3 = sub <1 x i32> zeroinitializer, %local
> +  br label %cond.end
> +
> +cond.false:
> +  br label %cond.end
> +
> +cond.end:
> +  %cond = phi <1 x i32> [ %phi3, %for.cond ], [ undef, %cond.false ]
> +  br label %cond.end47
> +
> +cond.end47:
> +  %sum = add <1 x i32> %cond, <i32 92>
> +  %phi2 = sub <1 x i32> zeroinitializer, %sum
> +  br label %for.cond
> +}
> 
> 
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