[llvm] r239015 - [ConstantFold] Don't skip the first gep index when folding geps

[David Blaikie]

On Thu, Jun 4, 2015 at 12:01 AM, David Majnemer <david.majnemer at gmail.com>
wrote:

> Author: majnemer
> Date: Thu Jun  4 02:01:56 2015
> New Revision: 239015
>
> URL: http://llvm.org/viewvc/llvm-project?rev=239015&view=rev
> Log:
> [ConstantFold] Don't skip the first gep index when folding geps
>
> We neglected to check if the first index made the GEP ineligible for
> 'inbounds'.
>

Thanks!


>
> This fixes PR23753.
>
> Added:
>     llvm/trunk/test/Transforms/LoopStrengthReduce/pr23753.ll
> Modified:
>     llvm/trunk/lib/IR/ConstantFold.cpp
>
> Modified: llvm/trunk/lib/IR/ConstantFold.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/ConstantFold.cpp?rev=239015&r1=239014&r2=239015&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/IR/ConstantFold.cpp (original)
> +++ llvm/trunk/lib/IR/ConstantFold.cpp Thu Jun  4 02:01:56 2015
> @@ -2165,9 +2165,9 @@ static Constant *ConstantFoldGetElementP
>    // factored out into preceding dimensions.
>    bool Unknown = false;
>    SmallVector<Constant *, 8> NewIdxs;
> -  Type *Ty = PointeeTy;
> -  Type *Prev = C->getType();
> -  for (unsigned i = 1, e = Idxs.size(); i != e;
> +  Type *Ty = C->getType();
> +  Type *Prev = nullptr;
> +  for (unsigned i = 0, e = Idxs.size(); i != e;
>         Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]),
> ++i) {
>      if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
>        if (isa<ArrayType>(Ty) || isa<VectorType>(Ty))
>
> Added: llvm/trunk/test/Transforms/LoopStrengthReduce/pr23753.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopStrengthReduce/pr23753.ll?rev=239015&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/LoopStrengthReduce/pr23753.ll (added)
> +++ llvm/trunk/test/Transforms/LoopStrengthReduce/pr23753.ll Thu Jun  4
> 02:01:56 2015
> @@ -0,0 +1,29 @@
> +; RUN: opt < %s -loop-reduce -S | FileCheck %s
> +
> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-unknown-linux-gnu"
> +
> + at a = external global i32, align 4
> + at d = external global i8, align 1
> +
> +; CHECK-LABEL: void @f
> +define void @f() {
> +entry:
> +  br label %for.body
> +
> +for.body:
> +  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
> +  %arrayidx = getelementptr inbounds i32, i32* @a, i64 %indvars.iv
> +  %cmp = icmp ne i32* %arrayidx, bitcast (i8* @d to i32*)
> +  %indvars.iv.next = add i64 %indvars.iv, 1
> +  br i1 %cmp, label %for.body, label %for.end
> +
> +; CHECK:       %[[phi:.*]] = phi i8* [ %[[gep:.*]], {{.*}} ], [
> getelementptr (i8, i8* @d, i64 sub (i64 4, i64 ptrtoint (i32* @a to i64))),
> {{.*}} ]
> +; CHECK-NEXT:  %[[gep]]    = getelementptr i8, i8* %[[phi]], i64 -4
> +; CHECK-NEXT:  %[[cst:.*]] = bitcast i8* %[[gep]] to i32*
> +; CHECK-NEXT:  %[[cmp:.*]] = icmp ne i32* %[[cst]], null
> +; CHECK-NEXT:  br i1 %[[cmp]]
> +
> +for.end:
> +  ret void
> +}
>
>
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