[llvm] r335294 - [GVN] Avoid casting a vector of size less than 8 bits to i8

[Davide Italiano via llvm-commits]

Glad to see this code in :)

On Thu, Jun 21, 2018 at 2:43 PM, Matthew Voss via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: ormris
> Date: Thu Jun 21 14:43:20 2018
> New Revision: 335294
>
> URL: http://llvm.org/viewvc/llvm-project?rev=335294&view=rev
> Log:
> [GVN] Avoid casting a vector of size less than 8 bits to i8
>
> Summary:
> A reprise of D25849.
>
> This crash was found through fuzzing some time ago and was documented in PR28879.
>
> No check for load size has been added due to the following tests:
>   - Transforms/GVN/invariant.group.ll
>   - Transforms/GVN/pr10820.ll
>
> These tests expect load sizes that are not a multiple of eight.
>
> Thanks to @davide for the original patch.
>
> Reviewers: nlopes, davide, RKSimon, reames, efriedma
>
> Reviewed By: efriedma
>
> Subscribers: davide, llvm-commits, Prazek
>
> Differential Revision: https://reviews.llvm.org/D48330
>
> Added:
>     llvm/trunk/test/Transforms/GVN/pr28879.ll
> Modified:
>     llvm/trunk/lib/Transforms/Utils/VNCoercion.cpp
>
> Modified: llvm/trunk/lib/Transforms/Utils/VNCoercion.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/VNCoercion.cpp?rev=335294&r1=335293&r2=335294&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/VNCoercion.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/VNCoercion.cpp Thu Jun 21 14:43:20 2018
> @@ -20,8 +20,14 @@ bool canCoerceMustAliasedValueToLoad(Val
>        StoredVal->getType()->isStructTy() || StoredVal->getType()->isArrayTy())
>      return false;
>
> +  uint64_t StoreSize = DL.getTypeSizeInBits(StoredVal->getType());
> +
> +  // The store size must be byte-aligned to support future type casts.
> +  if (llvm::alignTo(StoreSize, 8) != StoreSize)
> +    return false;
> +
>    // The store has to be at least as big as the load.
> -  if (DL.getTypeSizeInBits(StoredVal->getType()) < DL.getTypeSizeInBits(LoadTy))
> +  if (StoreSize < DL.getTypeSizeInBits(LoadTy))
>      return false;
>
>    // Don't coerce non-integral pointers to integers or vice versa.
>
> Added: llvm/trunk/test/Transforms/GVN/pr28879.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVN/pr28879.ll?rev=335294&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/GVN/pr28879.ll (added)
> +++ llvm/trunk/test/Transforms/GVN/pr28879.ll Thu Jun 21 14:43:20 2018
> @@ -0,0 +1,34 @@
> +; RUN: opt -gvn <%s -S -o - | FileCheck %s
> +
> +define void @f() {
> +entry:
> +  %a = alloca <7 x i1>, align 2
> +  store <7 x i1> undef, <7 x i1>* %a, align 2
> +; CHECK: store <7 x i1> undef, <7 x i1>*
> +  %0 = getelementptr inbounds <7 x i1>, <7 x i1>* %a, i64 0, i64 0
> +  %val = load i1, i1* %0, align 2
> +; CHECK: load i1, i1*
> +  br i1 %val, label %cond.true, label %cond.false
> +
> +cond.true:
> +  ret void
> +
> +cond.false:
> +  ret void
> +}
> +
> +define <7 x i1> @g(<7 x i1>* %a) {
> +entry:
> +  %vec = load <7 x i1>, <7 x i1>* %a
> +; CHECK: load <7 x i1>, <7 x i1>*
> +  %0 = getelementptr inbounds <7 x i1>, <7 x i1>* %a, i64 0, i64 0
> +  %val = load i1, i1* %0, align 2
> +; CHECK: load i1, i1*
> +  br i1 %val, label %cond.true, label %cond.false
> +
> +cond.true:
> +  ret <7 x i1> %vec
> +
> +cond.false:
> +  ret <7 x i1> <i1 false, i1 false, i1 false, i1 false, i1 false, i1 false, i1 false>
> +}
>
>
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-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare