[PATCH] Little improvement in IndVarSimplify

[Andrew Trick]

On Jul 11, 2013, at 12:29 AM, Michele Scandale <michele.scandale at gmail.com> wrote:

>  Here an updated version of the patch fixing code style as suggested by Andrew.

Committed r186107. Thanks.
-Andy

> 
>  Thanks again.
> 
>  Michele Scandale
> 
> Hi atrick,
> 
> http://llvm-reviews.chandlerc.com/D1112
> 
> CHANGE SINCE LAST DIFF
>  http://llvm-reviews.chandlerc.com/D1112?vs=2713&id=2765#toc
> 
> Files:
>  lib/Transforms/Scalar/IndVarSimplify.cpp
>  test/Transforms/IndVarSimplify/exitcnt-const-arstart-const-opt.ll
> 
> Index: lib/Transforms/Scalar/IndVarSimplify.cpp
> ===================================================================
> --- lib/Transforms/Scalar/IndVarSimplify.cpp
> +++ lib/Transforms/Scalar/IndVarSimplify.cpp
> @@ -1612,10 +1612,29 @@
>                << "  IVCount:\t" << *IVCount << "\n");
> 
>   IRBuilder<> Builder(BI);
> -  if (SE->getTypeSizeInBits(CmpIndVar->getType())
> -      > SE->getTypeSizeInBits(ExitCnt->getType())) {
> -    CmpIndVar = Builder.CreateTrunc(CmpIndVar, ExitCnt->getType(),
> -                                    "lftr.wideiv");
> +
> +  unsigned CmpIndVarSize = SE->getTypeSizeInBits(CmpIndVar->getType());
> +  unsigned ExitCntSize = SE->getTypeSizeInBits(ExitCnt->getType());
> +  if (CmpIndVarSize > ExitCntSize) {
> +    const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(SE->getSCEV(IndVar));
> +    const SCEV *ARStart = AR->getStart();
> +    const SCEV *ARStep = AR->getStepRecurrence(*SE);
> +    if (isa<SCEVConstant>(ARStart) && isa<SCEVConstant>(IVCount)) {
> +      const APInt &Start = cast<SCEVConstant>(ARStart)->getValue()->getValue();
> +      const APInt &Count = cast<SCEVConstant>(IVCount)->getValue()->getValue();
> +
> +      APInt NewLimit;
> +      if (cast<SCEVConstant>(ARStep)->getValue()->isNegative())
> +        NewLimit = Start - Count.zext(CmpIndVarSize);
> +      else
> +        NewLimit = Start + Count.zext(CmpIndVarSize);
> +      ExitCnt = ConstantInt::get(CmpIndVar->getType(), NewLimit);
> +
> +      DEBUG(dbgs() << "  Widen RHS:\t" << *ExitCnt << "\n");
> +    } else {
> +      CmpIndVar = Builder.CreateTrunc(CmpIndVar, ExitCnt->getType(),
> +                                      "lftr.wideiv");
> +    }
>   }
> 
>   Value *Cond = Builder.CreateICmp(P, CmpIndVar, ExitCnt, "exitcond");
> Index: test/Transforms/IndVarSimplify/exitcnt-const-arstart-const-opt.ll
> ===================================================================
> --- test/Transforms/IndVarSimplify/exitcnt-const-arstart-const-opt.ll
> +++ test/Transforms/IndVarSimplify/exitcnt-const-arstart-const-opt.ll
> @@ -0,0 +1,25 @@
> +;RUN: opt -S %s -indvars | FileCheck %s
> +
> +; Function Attrs: nounwind uwtable
> +define void @foo() #0 {
> +entry:
> +  br label %for.body
> +
> +for.body:                                         ; preds = %entry, %for.body
> +  %i.01 = phi i16 [ 0, %entry ], [ %inc, %for.body ]
> +  %conv2 = sext i16 %i.01 to i32
> +  call void @bar(i32 %conv2) #1
> +  %inc = add i16 %i.01, 1
> +;CHECK-NOT: %lftr.wideiv = trunc i32 %indvars.iv.next to i16
> +;CHECK: %exitcond = icmp ne i32 %indvars.iv.next, 512
> +  %cmp = icmp slt i16 %inc, 512
> +  br i1 %cmp, label %for.body, label %for.end
> +
> +for.end:                                          ; preds = %for.body
> +  ret void
> +}
> +
> +declare void @bar(i32)
> +
> +attributes #0 = { nounwind uwtable }
> +attributes #1 = { nounwind }
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