[llvm] r353911 - [LoopSimplifyCFG] Re-enable const branch folding by default

[Alina Sbirlea via llvm-commits]

Are you sure your update is complete?
It should theoretically match the DT update, i.e. include insert edges not
just the delete. All updates should be done together using the same list of
updates used for DT, and an up to date DT (see
MSSAU->applyUpdates(DTUpdates, DT)).

On Wed, Feb 20, 2019 at 9:53 PM Maxim Kazantsev via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Should be fixed by https://reviews.llvm.org/rL354547
>
>
>
> *From:* Maxim Kazantsev
> *Sent:* Thursday, February 21, 2019 11:49 AM
> *To:* 'rtereshin at apple.com' <rtereshin at apple.com>
> *Cc:* llvm-commits <llvm-commits at lists.llvm.org>; dberlin at dberlin.org;
> asbirlea at google.com
> *Subject:* RE: [llvm] r353911 - [LoopSimplifyCFG] Re-enable const branch
> folding by default
>
>
>
> Hi Roman,
>
>
>
> Thanks for notification! I’ll fix it asap.
>
>
>
> --Max
>
>
>
> *From:* rtereshin at apple.com <rtereshin at apple.com>
> *Sent:* Thursday, February 21, 2019 10:25 AM
> *To:* Maxim Kazantsev <max.kazantsev at azul.com>
> *Cc:* llvm-commits <llvm-commits at lists.llvm.org>; dberlin at dberlin.org;
> asbirlea at google.com
> *Subject:* Re: [llvm] r353911 - [LoopSimplifyCFG] Re-enable const branch
> folding by default
>
>
>
> Hi Max,
>
> Looks like this doesn’t collaborate with MemorySSA very well:
>
> ./bin/opt -loop-simplifycfg
> loop-simplifycfg-term-folding-AND-mssa-loop-dependency.ll
> -enable-mssa-loop-dependency=true -verify-memoryssa=true
> -enable-loop-simplifycfg-term-folding=true -S -o -
> Assertion failed: (find(predecessors(&B), Phi->getIncomingBlock(I)) !=
> pred_end(&B) && "Incoming phi block not a block predecessor"), function
> verifyDefUses, file ../lib/Analysis/MemorySSA.cpp, line 1947.
>
> The IR is:
>
> define void @main() {
> entry:
>   br label %for.body
>
> for.body:                                         ; preds = %exit, %entry
>   br label %switch.bb
>
> switch.bb:                                        ; preds = %for.body
>   switch i2 1, label %default.bb [
>     i2 1, label %case.bb
>   ]
>
> case.bb:                                          ; preds = %switch
>   br label %exit
>
> default.bb:                                       ; preds = %switch
>   unreachable
>
> exit:                                             ; preds = %case.bb
>   call void @foo()
>   br label %for.body
> }
>
> declare void @foo()
>
>
> Thanks,
> Roman
>
>
>
> > On Feb 12, 2019, at 10:12 PM, Max Kazantsev via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
> >
> > Author: mkazantsev
> > Date: Tue Feb 12 22:12:48 2019
> > New Revision: 353911
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=353911&view=rev
> > Log:
> > [LoopSimplifyCFG] Re-enable const branch folding by default
> >
> > Known underlying bugs have been fixed, intensive fuzz testing did not
> > find any new problems. Re-enabling by default. Feel free to revert if
> > it causes any functional failures.
> >
> > Modified:
> >    llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
> >
> > Modified: llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp?rev=353911&r1=353910&r2=353911&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp (original)
> > +++ llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp Tue Feb 12
> 22:12:48 2019
> > @@ -41,7 +41,7 @@ using namespace llvm;
> > #define DEBUG_TYPE "loop-simplifycfg"
> >
> > static cl::opt<bool>
> EnableTermFolding("enable-loop-simplifycfg-term-folding",
> > -                                       cl::init(false));
> > +                                       cl::init(true));
> >
> > STATISTIC(NumTerminatorsFolded,
> >           "Number of terminators folded to unconditional branches");
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at lists.llvm.org
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