[llvm] 22a5cde - [SCEV] Separate out constant folding in mul expr creation

[Florian Hahn via llvm-commits]

> On Jun 20, 2021, at 15:22, Nikita Popov <nikita.ppv at gmail.com> wrote:
> 
> On Sun, Jun 20, 2021 at 12:24 PM Florian Hahn <florian_hahn at apple.com <mailto:florian_hahn at apple.com>> wrote:
> Hi,
> 
>> On Oct 25, 2020, at 17:47, Nikita Popov via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
>> 
>> 
>> Author: Nikita Popov
>> Date: 2020-10-25T18:46:50+01:00
>> New Revision: 22a5cde541c3306e53279fd02c6d60ae6178ef10
>> 
>> URL: https://github.com/llvm/llvm-project/commit/22a5cde541c3306e53279fd02c6d60ae6178ef10 <https://github.com/llvm/llvm-project/commit/22a5cde541c3306e53279fd02c6d60ae6178ef10>
>> DIFF: https://github.com/llvm/llvm-project/commit/22a5cde541c3306e53279fd02c6d60ae6178ef10.diff <https://github.com/llvm/llvm-project/commit/22a5cde541c3306e53279fd02c6d60ae6178ef10.diff>
>> 
>> LOG: [SCEV] Separate out constant folding in mul expr creation
>> 
>> Separate out the code handling constant folding into a separate
>> block, that is independent of other folds that need a constant
>> first operand. Also make some minor adjustments to make the
>> constant folding look nearly identical to the same code in
>> getAddExpr().
>> 
>> The only reason this change is not strictly NFC is that the
>> C1*(C2+V) fold is moved below the constant folding, which means
>> that it now also applies to C1*C2*(C3+V), as it should.
>> 
>> Added: 
> 
> 
> It looks like this change may cause a crash in LoopStrengthReduce: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35400 <https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35400>
> 
> To reproduce, run `llc` on  https://oss-fuzz.com/download?testcase_id=5243727227518976 <https://oss-fuzz.com/download?testcase_id=5243727227518976>
> 
> Looks like this is https://bugs.llvm.org/show_bug.cgi?id=50765 <https://bugs.llvm.org/show_bug.cgi?id=50765>.
> 
> Nikita


Sounds good, thanks!

Cheers,
Florian
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