[llvm] 8d20f2c - Revert "[CodeGenPrepare] Fix isIVIncrement (PR49466)"

Philip Reames via llvm-commits llvm-commits at lists.llvm.org
Fri Mar 12 16:08:27 PST 2021


On 3/12/21 3:55 PM, Mehdi AMINI wrote:
> Hey Philip,
>
> On Fri, Mar 12, 2021 at 3:22 PM Philip Reames via llvm-commits 
> <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
>
>
>     On 3/12/21 2:59 PM, Jordan Rupprecht wrote:
>>
>>
>>     On Fri, Mar 12, 2021 at 4:29 PM Philip Reames
>>     <listmail at philipreames.com <mailto:listmail at philipreames.com>> wrote:
>>
>>         Jordan,
>>
>>         Please revert this change.
>>
>>         There's a couple of problems here:
>>
>>           * The change reverted looks obviously innocent.  (e.g. it's
>>             bailing out of a transform slightly more often)
>>
>>     I don't disagree that it "looks obviously innocent", but the
>>     proof is in the pudding: the reproducer I posted compiles
>>     ~instantly at one commit prior, and times out at the culprit
>>     commit. A change "looking" good should never be a basis for
>>     saying it must be correct and should not be reverted, especially
>>     when there is evidence it is a problem. At least, that's my
>>     personal opinion, but I should think that's a fairly basic and
>>     widely held belief.
>
>     You're correct, but missing the point I was getting at. 
>     Admittedly, poorly worded.
>
>     While looking obviously innocent isn't reason not to revert
>     itself, it's definitely reason to take a slightly closer look and
>     make sure there's nothing else going on.  This is particularly
>     relevant given the other points in this discussion.
>
>>           * The change reverted was itself fixing a functional bug. 
>>             At a minimum, we'd need a larger revert to get ToT back
>>             to a sane state.
>>
>>     The fix is introducing a different bug, and one which seems more
>>     widespread. At the very least, we haven't observed any of the
>>     crashes mentioned in PR49466, but we did notice a compile timeout
>>     in several different compilation units.
>
>     Bug?  Discussion?  Response to original commit?
>
>     Your observation may be true *for you*.  It is not necessarily
>     true for anyone else, and you bear the burden of making the case. 
>     Particularly when reverting a functional fix.
>
>
> Sure, the author of the revert bears the burden of providing 
> everything needed for the reproduction, but that does not mean we 
> shouldn't revert first and talk it through when a problem is detected. 
> I've been frequently reverting patches when there were obvious 
> regressions and saying "I'm still working on reducing the test case" 
> (which frequently required making it into something that won't leak 
> proprietary data...).

So, let's start with the acknowledgement that all of this is 
complicated.  There's no absolutes here.

Having said that, given the whole of the circumstances, I do not feel 
that the implied burden of proof was met for this revert, in this 
specific case.  As has been acknowledged, the revert was rushed (i.e. no 
public mention of a problem before revert after a change had been in 
tree for days).  If that hadn't been the case, the implied bar would be 
much lower.

>
> It also seems to me that providing a clang test case that repro at 
> head is enough, I have no problem generating IR if the author is 
> asking me to, but I don't consider this like a prerequisite to revert 
> either: clang is in-tree and like every project in-tree we shouldn't 
> regress it unknowingly and/or without coordination.

Again, whole of circumstances.  For a rushed revert, days after 
submission, with no prior discussion, burden is on the reverter. If this 
had been a hour or two after commit, I'd have no problem with a C/C++ 
example, or a link to a build bot.  That was not the case here.

On the in tree point you make, I will not agree that "just because 
something is in tree" there's no burden of reduction for a case like 
this.  Take your paragraph and replace "clang" with "flang", or "mlir" 
or "gn build", do you still feel the same way?

I'll warn you, this is a hill I'm willing to die on.  :)  It both 
affects my personal workflows immensely, and is also something I see as 
being really important to community as a whole.  I will say that if you 
want to discuss this in abstract (not specific to the particular revert 
in question), we should probably move this to an llvm-dev thread.


>     To be clear, I'm not saying you're wrong.  I'm saying you haven't
>     given anyone else enough information to tell if you are or not.
>
>>           * It is generally considered reasonable to provide a test
>>             case and wait a bit before reverting, at least once the
>>             patch is more than a few hours old.
>>
>>     Sorry about that. I'll concede that I got a little trigger happy
>>     here, but I was hoping that would be waived by the fact that I
>>     gave a simple, concrete reproducer.
>     Thanks for the acknowledgement.  To be fair, it would have been
>     less of an issue if the reproducer worked straight forwardly.
>>
>>           * Failure to provide an IR test case.
>>
>>     (ditto, but see one below)
>>
>>           * Your test case does not reproduce.  Or at least, it
>>             doesn't reproduce when compiled with clang10 to IR and
>>             then run through (very recent, but without your change)
>>             ToT opt -O2.  If there's something specific about the
>>             interaction of clang and opt ToT, reducing this down to a
>>             IR test case becomes particularly important.
>>
>>     This comment is going *way* off track -- the reproducer I posted
>>     *does* reproduce, at least for me, in the configuration I posted
>>     (a C++ source file, and just "clang -O2"). By saying it doesn't
>>     reproduce in a mixed configuration of an old version of clang to
>>     do the C++ -> IR combined with a ToT version of opt -O2 to do the
>>     IR -> object file is misleading -- it's true, but that's not at
>>     all what I was claiming, and I don't know where it's coming from.
>
>     I actually don't think this is going off track at all.  Our
>     default is for IR test cases for IR problems.  Any reverting
>     commit should generally include a test case suitable for checkin
>     (w/a bit of cleanup) once the patch is fixed.  I'll admit, we're
>     not strict about this, but the expectation is definitely there.
>
> I wasn't aware of this expectation, in general I expect a reproducer 
> that reproduces *in-tree*.
> Just last week I reverted a case where it broke the bootstrap of 
> clang, I am not working on clang but I have a bot that bootstrap clang 
> and then I use this clang to test my code. I consider myself doing a 
> community service by reverting fast and providing reproduction 
> instructions to the author.
> However I believe that the burden of debugging this will be on the 
> patch author, even though the author is purely changing an LLVM IR 
> pass. I wouldn't go and debug stage 2 and minimize and IR reproducer 
> from the clang pipeline when many bots are broken.
See my point above about whole of circumstances and timeframes.
>
>     The discussion of the hybrid configuration is relevant *because*
>     you didn't provide a test case in a form I could easily use.  I
>     don't work on clang, don't build it regularly, and shouldn't have
>     to investigate a LLVM codegen regression.
>
> I am not sure we have a wide agreement here: as an author you may ask 
> for help to get a smaller repro, but my take is that if you break 
> clang you may have to build it yourself. In the example above, I 
> provided the cmake invocation that would make it crash in stage2. This 
> is hermetic in the monorepo, does not require any external dependency, 
> I hope it passes the bar for revert and reproducer.
>
> Maybe we should have a larger discussion about this on llvm-dev@ and 
> document this all? Apparently we have different implicit assumptions 
> here, because over the years it seemed normal to me to receive C++ 
> input example when I broke clang with my LLVM changes

See above, but yes, some broader discussion may be warranted.  I don't 
think my take is out of line with historical practice, but it may be 
time to document that if we're getting disagreement.

If you start the thread, please try to reflect the complexities and the 
differences different timeframes bring into discussion.

>
> Cheers,
>
> -- 
> Mehdi
>
>
>     (See also below.)
>
>>         Philip
>>
>>         p.s. To be clear, I'm happy to look at your original issue
>>         this afternoon if you've got something I can reproduce.
>>
>>     Here's an IR reproducer with IR generated from ToT before my
>>     revert (at dfd27ebbd0eb137c9a439b7c537bb87ba903efd3):
>
>     Ok, we have a problem here.  None of the following reproduce for me:
>
>     $ ./llc -O2 jordan.ll
>     $ ./llc -O2 jordan.ll
>     $ ./llc -O2 jordan.ll --filetype=obj
>     $ ./llc -O3 jordan.ll --filetype=obj
>
>     LLC is ToT, just built with your change reverted locally.
>
>>     $ bin/clang -c /tmp/repro.cc -O1 -S -emit-llvm -o /tmp/repro.ll
>>     $ bin/clang -c /tmp/repro.ll -O2 -o /tmp/repro.o  # hangs
>
>     Given the preceding, I am now asserting this is likely some clang
>     specific problem.  I've got a build of clang running now, will
>     report back in a bit.
>
>     The other option is that this is someway specific to your
>     configuration.
>
>
>>
>>     ; ModuleID = '/tmp/repro.cc'
>>     source_filename = "/tmp/repro.cc"
>>     target datalayout =
>>     "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
>>     target triple = "x86_64-unknown-linux-gnu"
>>
>>     %class.D = type { i64 }
>>     %class.a = type { %class.g }
>>     %class.g = type { i32*, i32* }
>>
>>     $_ZNK1aIliEixEl = comdat any
>>
>>     $_ZNK1aIliE1jEv = comdat any
>>
>>     @o = dso_local local_unnamed_addr global i32 0, align 4
>>     @p = dso_local local_unnamed_addr global i32 0, align 4
>>     @.str = private unnamed_addr constant [1 x i8] zeroinitializer,
>>     align 1
>>
>>     ; Function Attrs: uwtable mustprogress
>>     define dso_local void @_ZN1D1qERK1aIliE(%class.D* nocapture
>>     nonnull dereferenceable(8) %0, %class.a* nonnull align 8
>>     dereferenceable(16) %1) local_unnamed_addr #0 align 2 {
>>       %3 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull
>>     dereferenceable(16) %1, i64 0) #3
>>       %4 = icmp eq i64 %3, 0
>>       br i1 %4, label %26, label %5
>>
>>     5:  ; preds = %2
>>       %6 = call i64 @_ZNK1aIliE1jEv(%class.a* nonnull
>>     dereferenceable(16) %1)
>>       %7 = icmp eq i64 %6, 0
>>       br i1 %7, label %26, label %8
>>
>>     8:  ; preds = %5
>>       %9 = getelementptr inbounds %class.D, %class.D* %0, i64 0, i32 0
>>       br label %10
>>
>>     10:   ; preds = %8, %18
>>       %11 = phi i64 [ 0, %8 ], [ %23, %18 ]
>>       %12 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull
>>     dereferenceable(16) %1, i64 %11) #3
>>       %13 = icmp eq i64 %12, 0
>>       br i1 %13, label %18, label %14
>>
>>     14:   ; preds = %10, %14
>>       %15 = load i32, i32* @o, align 4, !tbaa !2
>>       %16 = call i32 @_Z3fn1IiiEiT_T0_PKc(i32 %15, i32 0, i8*
>>     getelementptr inbounds ([1 x i8], [1 x i8]* @.str, i64 0, i64 0))
>>       %17 = icmp eq i32 %16, 0
>>       br i1 %17, label %18, label %14, !llvm.loop !6
>>
>>     18:   ; preds = %14, %10
>>       %19 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull
>>     dereferenceable(16) %1, i64 %11) #3
>>       %20 = load i32, i32* @p, align 4, !tbaa !2
>>       %21 = sext i32 %20 to i64
>>       %22 = sdiv i64 %19, %21
>>       store i64 %22, i64* %9, align 8, !tbaa !9
>>       %23 = add i64 %11, 1
>>       %24 = call i64 @_ZNK1aIliE1jEv(%class.a* nonnull
>>     dereferenceable(16) %1)
>>       %25 = icmp eq i64 %24, 0
>>       br i1 %25, label %26, label %10, !llvm.loop !12
>>
>>     26:   ; preds = %18, %5, %2
>>       ret void
>>     }
>>
>>     ; Function Attrs: nounwind uwtable willreturn mustprogress
>>     define linkonce_odr dso_local i64 @_ZNK1aIliEixEl(%class.a*
>>     nonnull dereferenceable(16) %0, i64 %1) local_unnamed_addr #1
>>     comdat align 2 {
>>       %3 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32
>>     0, i32 0
>>       %4 = load i32*, i32** %3, align 8, !tbaa !13
>>       %5 = getelementptr inbounds i32, i32* %4, i64 %1
>>       %6 = load i32, i32* %5, align 4, !tbaa !2
>>       %7 = sext i32 %6 to i64
>>       ret i64 %7
>>     }
>>
>>     ; Function Attrs: nounwind uwtable willreturn mustprogress
>>     define linkonce_odr dso_local i64 @_ZNK1aIliE1jEv(%class.a*
>>     nonnull dereferenceable(16) %0) local_unnamed_addr #1 comdat
>>     align 2 {
>>       %2 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32
>>     0, i32 1
>>       %3 = load i32*, i32** %2, align 8, !tbaa !16
>>       %4 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32
>>     0, i32 0
>>       %5 = load i32*, i32** %4, align 8, !tbaa !13
>>       %6 = ptrtoint i32* %3 to i64
>>       %7 = ptrtoint i32* %5 to i64
>>       %8 = sub i64 %6, %7
>>       %9 = ashr exact i64 %8, 2
>>       ret i64 %9
>>     }
>>
>>     declare dso_local i32 @_Z3fn1IiiEiT_T0_PKc(i32, i32, i8*)
>>     local_unnamed_addr #2
>>
>>     attributes #0 = { uwtable mustprogress "frame-pointer"="none"
>>     "no-trapping-math"="true" "stack-protector-buffer-size"="8"
>>     "target-cpu"="x86-64"
>>     "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87"
>>     "tune-cpu"="generic" }
>>     attributes #1 = { nounwind uwtable willreturn mustprogress
>>     "frame-pointer"="none" "no-trapping-math"="true"
>>     "stack-protector-buffer-size"="8" "target-cpu"="x86-64"
>>     "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87"
>>     "tune-cpu"="generic" }
>>     attributes #2 = { "frame-pointer"="none"
>>     "no-trapping-math"="true" "stack-protector-buffer-size"="8"
>>     "target-cpu"="x86-64"
>>     "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87"
>>     "tune-cpu"="generic" }
>>     attributes #3 = { nounwind }
>>
>>     !llvm.module.flags = !{!0}
>>     !llvm.ident = !{!1}
>>
>>     !0 = !{i32 1, !"wchar_size", i32 4}
>>     !1 = !{!"clang version 13.0.0
>>     (https://github.com/llvm/llvm-project.git
>>     <https://github.com/llvm/llvm-project.git>
>>     dfd27ebbd0eb137c9a439b7c537bb87ba903efd3)"}
>>     !2 = !{!3, !3, i64 0}
>>     !3 = !{!"int", !4, i64 0}
>>     !4 = !{!"omnipotent char", !5, i64 0}
>>     !5 = !{!"Simple C++ TBAA"}
>>     !6 = distinct !{!6, !7, !8}
>>     !7 = !{!"llvm.loop.mustprogress"}
>>     !8 = !{!"llvm.loop.unroll.disable"}
>>     !9 = !{!10, !11, i64 0}
>>     !10 = !{!"_ZTS1D", !11, i64 0}
>>     !11 = !{!"long", !4, i64 0}
>>     !12 = distinct !{!12, !7, !8}
>>     !13 = !{!14, !15, i64 0}
>>     !14 = !{!"_ZTS1g", !15, i64 0, !15, i64 8}
>>     !15 = !{!"any pointer", !4, i64 0}
>>     !16 = !{!14, !15, i64 8}
>>
>>         On 3/12/21 1:59 PM, Jordan Rupprecht via llvm-commits wrote:
>>>         Author: Jordan Rupprecht
>>>         Date: 2021-03-12T13:59:14-08:00
>>>         New Revision: 8d20f2c2c66eb486ff23cc3d55a53bd840b36971
>>>
>>>         URL:https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971  <https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971>
>>>         DIFF:https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971.diff  <https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971.diff>
>>>
>>>         LOG: Revert "[CodeGenPrepare] Fix isIVIncrement (PR49466)"
>>>
>>>         This reverts commit cf82700af8c658ae09b14c3d01bb1e73e48d3bd3 due to a compile timeout when building the following with `clang -O2`:
>>>
>>>         ```
>>>         template <class, class = int> class a;
>>>         struct b {
>>>            using d = int *;
>>>         };
>>>         struct e {
>>>            using f = b::d;
>>>         };
>>>         class g {
>>>         public:
>>>            e::f h;
>>>            e::f i;
>>>         };
>>>         template <class, class> class a : g {
>>>         public:
>>>            long j() const { return i - h; }
>>>            long operator[](long) const noexcept;
>>>         };
>>>         template <class c, class k> long a<c, k>::operator[](long l) const noexcept {
>>>            return h[l];
>>>         }
>>>         template <typename m, typename n> int fn1(m, n, const char *);
>>>         int o, p;
>>>         class D {
>>>            void q(const a<long> &);
>>>            long r;
>>>         };
>>>         void D::q(const a<long> &l) {
>>>            int s;
>>>            if (l[0])
>>>              for (; l.j(); ++s) {
>>>                if (l[s])
>>>                  while (fn1(o, 0, ""))
>>>                    ;
>>>                r = l[s] / p;
>>>              }
>>>         }
>>>         ```
>>>
>>>         Added:
>>>              
>>>
>>>         Modified:
>>>              llvm/lib/CodeGen/CodeGenPrepare.cpp
>>>
>>>         Removed:
>>>              llvm/test/CodeGen/X86/pr49466.ll
>>>
>>>
>>>         ################################################################################
>>>         diff  --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
>>>         index 0f698dd3b190..0b1156e2ace7 100644
>>>         --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
>>>         +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
>>>         @@ -1332,7 +1332,7 @@ getIVIncrement(const PHINode *PN, const LoopInfo *LI) {
>>>           
>>>           static bool isIVIncrement(const BinaryOperator *BO, const LoopInfo *LI) {
>>>             auto *PN = dyn_cast<PHINode>(BO->getOperand(0));
>>>         -  if (!PN || LI->getLoopFor(BO->getParent()) != LI->getLoopFor(PN->getParent()))
>>>         +  if (!PN)
>>>               return false;
>>>             if (auto IVInc = getIVIncrement(PN, LI))
>>>               return IVInc->first == BO;
>>>         @@ -1347,7 +1347,6 @@ bool CodeGenPrepare::replaceMathCmpWithIntrinsic(BinaryOperator *BO,
>>>               if (!isIVIncrement(BO, LI))
>>>                 return false;
>>>               const Loop *L = LI->getLoopFor(BO->getParent());
>>>         -    assert(L && "L should not be null after isIVIncrement()");
>>>               // Do not risk on moving increment into a child loop.
>>>               if (LI->getLoopFor(Cmp->getParent()) != L)
>>>                 return false;
>>>
>>>         diff  --git a/llvm/test/CodeGen/X86/pr49466.ll b/llvm/test/CodeGen/X86/pr49466.ll
>>>         deleted file mode 100644
>>>         index 4f6574d9bbf2..000000000000
>>>         --- a/llvm/test/CodeGen/X86/pr49466.ll
>>>         +++ /dev/null
>>>         @@ -1,122 +0,0 @@
>>>         -; RUN: opt < %s -O2 -codegenprepare -S | FileCheck %s
>>>         -
>>>         -target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
>>>         -target triple = "x86_64-unknown-linux-gnu"
>>>         -
>>>         - at b = dso_local local_unnamed_addr global i64 0, align 8
>>>         - at c = dso_local local_unnamed_addr global i64 0, align 8
>>>         - at d = dso_local local_unnamed_addr global i64 0, align 8
>>>         - at e = dso_local local_unnamed_addr global i64 0, align 8
>>>         - at f = dso_local local_unnamed_addr global i64 0, align 8
>>>         - at g = dso_local local_unnamed_addr global i64 0, align 8
>>>         -
>>>         -; CHECK-LABEL: @m(
>>>         -
>>>         -define dso_local i32 @m() local_unnamed_addr {
>>>         -entry:
>>>         -  %0 = load i64, i64* @f, align 8
>>>         -  %1 = inttoptr i64 %0 to i32*
>>>         -  %2 = load i64, i64* @c, align 8
>>>         -  %conv18 = trunc i64 %2 to i32
>>>         -  %cmp = icmp slt i32 %conv18, 3
>>>         -  %3 = load i64, i64* @d, align 8
>>>         -  %conv43 = trunc i64 %3 to i8
>>>         -  %tobool40.not = icmp eq i8 %conv43, 0
>>>         -  br label %for.cond
>>>         -
>>>         -for.cond:                                         ; preds = %for.cond39.preheader, %entry
>>>         -  %j.0 = phi i32 [ undef, %entry ], [ %j.1.lcssa, %for.cond39.preheader ]
>>>         -  %p.0 = phi i64 [ undef, %entry ], [ %p.1.lcssa, %for.cond39.preheader ]
>>>         -  %i.0 = phi i32 [ undef, %entry ], [ %i.1.lcssa, %for.cond39.preheader ]
>>>         -  %cmp73 = icmp slt i32 %i.0, 3
>>>         -  br i1 %cmp73, label %for.body.preheader, label %for.cond39.preheader
>>>         -
>>>         -for.body.preheader:                               ; preds = %for.cond
>>>         -  br label %for.body
>>>         -
>>>         -for.cond1.loopexit:                               ; preds = %for.inc34.preheader, %for.end12
>>>         -  br i1 %cmp, label %for.body, label %for.cond39.preheader.loopexit
>>>         -
>>>         -for.cond39.preheader.loopexit:                    ; preds = %for.cond1.loopexit
>>>         -  br label %for.cond39.preheader
>>>         -
>>>         -for.cond39.preheader:                             ; preds = %for.cond39.preheader.loopexit, %for.cond
>>>         -  %j.1.lcssa = phi i32 [ %j.0, %for.cond ], [ %conv18, %for.cond39.preheader.loopexit ]
>>>         -  %p.1.lcssa = phi i64 [ %p.0, %for.cond ], [ 0, %for.cond39.preheader.loopexit ]
>>>         -  %i.1.lcssa = phi i32 [ %i.0, %for.cond ], [ %conv18, %for.cond39.preheader.loopexit ]
>>>         -  br i1 %tobool40.not, label %for.cond, label %for.inc42.preheader
>>>         -
>>>         -for.inc42.preheader:                              ; preds = %for.cond39.preheader
>>>         -  br label %for.inc42
>>>         -
>>>         -for.body:                                         ; preds = %for.body.preheader, %for.cond1.loopexit
>>>         -  %l.176 = phi i8 [ %sub, %for.cond1.loopexit ], [ 0, %for.body.preheader ]
>>>         -  %p.175 = phi i64 [ 0, %for.cond1.loopexit ], [ %p.0, %for.body.preheader ]
>>>         -  %j.174 = phi i32 [ %conv18, %for.cond1.loopexit ], [ %j.0, %for.body.preheader ]
>>>         -  %tobool.not = icmp eq i32 %j.174, 0
>>>         -  br i1 %tobool.not, label %cleanup45, label %for.cond2.preheader
>>>         -
>>>         -for.cond2.preheader:                              ; preds = %for.body
>>>         -  %tobool3.not69 = icmp eq i64 %p.175, 0
>>>         -  %.pr.pre = load i64, i64* @e, align 8
>>>         -  br i1 %tobool3.not69, label %for.end12, label %for.body4.preheader
>>>         -
>>>         -for.body4.preheader:                              ; preds = %for.cond2.preheader
>>>         -  %4 = sub i64 0, %p.175
>>>         -  %xtraiter = and i64 %4, 7
>>>         -  %lcmp.mod.not = icmp eq i64 %xtraiter, 0
>>>         -  br i1 %lcmp.mod.not, label %for.body4.prol.loopexit, label %for.body4.prol.preheader
>>>         -
>>>         -for.body4.prol.preheader:                         ; preds = %for.body4.preheader
>>>         -  %5 = mul nsw i64 %xtraiter, -1
>>>         -  br label %for.body4.prol
>>>         -
>>>         -for.body4.prol:                                   ; preds = %for.body4.prol.preheader, %for.body4.prol
>>>         -  %lsr.iv = phi i64 [ 0, %for.body4.prol.preheader ], [ %lsr.iv.next, %for.body4.prol ]
>>>         -  %lsr.iv.next = add nsw i64 %lsr.iv, -1
>>>         -  %prol.iter.cmp.not = icmp eq i64 %5, %lsr.iv.next
>>>         -  br i1 %prol.iter.cmp.not, label %for.body4.prol.loopexit.loopexit, label %for.body4.prol
>>>         -
>>>         -for.body4.prol.loopexit.loopexit:                 ; preds = %for.body4.prol
>>>         -  %6 = sub i64 %p.175, %lsr.iv.next
>>>         -  br label %for.body4.prol.loopexit
>>>         -
>>>         -for.body4.prol.loopexit:                          ; preds = %for.body4.prol.loopexit.loopexit, %for.body4.preheader
>>>         -  %p.270.unr = phi i64 [ %p.175, %for.body4.preheader ], [ %6, %for.body4.prol.loopexit.loopexit ]
>>>         -  %7 = icmp ugt i64 %p.175, -8
>>>         -  br i1 %7, label %for.end12, label %for.body4.preheader89
>>>         -
>>>         -for.body4.preheader89:                            ; preds = %for.body4.prol.loopexit
>>>         -  br label %for.body4
>>>         -
>>>         -for.body4:                                        ; preds = %for.body4.preheader89, %for.body4
>>>         -  %p.270 = phi i64 [ %inc11.7, %for.body4 ], [ %p.270.unr, %for.body4.preheader89 ]
>>>         -  %inc11.7 = add i64 %p.270, 8
>>>         -  %tobool3.not.7 = icmp eq i64 %inc11.7, 0
>>>         -  br i1 %tobool3.not.7, label %for.end12.loopexit, label %for.body4
>>>         -
>>>         -for.end12.loopexit:                               ; preds = %for.body4
>>>         -  br label %for.end12
>>>         -
>>>         -for.end12:                                        ; preds = %for.end12.loopexit, %for.body4.prol.loopexit, %for.cond2.preheader
>>>         -  %8 = load i32, i32* %1, align 4
>>>         -  %conv23 = zext i32 %8 to i64
>>>         -  %9 = load i64, i64* @b, align 8
>>>         -  %div24 = udiv i64 %9, %conv23
>>>         -  store i64 %div24, i64* @b, align 8
>>>         -  %sub = add i8 %l.176, -1
>>>         -  %tobool32.not72 = icmp eq i64 %.pr.pre, 0
>>>         -  br i1 %tobool32.not72, label %for.cond1.loopexit, label %for.inc34.preheader
>>>         -
>>>         -for.inc34.preheader:                              ; preds = %for.end12
>>>         -  store i64 0, i64* @e, align 8
>>>         -  br label %for.cond1.loopexit
>>>         -
>>>         -for.inc42:                                        ; preds = %for.inc42.preheader, %for.inc42
>>>         -  br label %for.inc42
>>>         -
>>>         -cleanup45:                                        ; preds = %for.body
>>>         -  %cmp13 = icmp ne i8 %l.176, 0
>>>         -  %conv16 = zext i1 %cmp13 to i32
>>>         -  ret i32 %conv16
>>>         -}
>>>
>>>
>>>                  
>>>         _______________________________________________
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>>>         llvm-commits at lists.llvm.org  <mailto:llvm-commits at lists.llvm.org>
>>>         https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits  <https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits>
>>
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