<div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Mar 12, 2021 at 4:29 PM Philip Reames <<a href="mailto:listmail@philipreames.com">listmail@philipreames.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>Jordan,</p>
<p>Please revert this change.</p>
<p>There's a couple of problems here:</p>
<ul>
<li>The change reverted looks obviously innocent. (e.g. it's
bailing out of a transform slightly more often)</li></ul></div></blockquote><div>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.</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><ul>
<li>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.</li></ul></div></blockquote><div>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.</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><ul>
<li>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.</li></ul></div></blockquote><div>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. </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><ul>
<li>Failure to provide an IR test case.</li></ul></div></blockquote><div>(ditto, but see one below) </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><ul>
<li>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.</li></ul></div></blockquote><div>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.</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><ul>
</ul>
<p>Philip<br>
</p>
<p>p.s. To be clear, I'm happy to look at your original issue this
afternoon if you've got something I can reproduce.</p></div></blockquote><div>Here's an IR reproducer with IR generated from ToT before my revert (at dfd27ebbd0eb137c9a439b7c537bb87ba903efd3):</div><div>$ bin/clang -c /tmp/repro.cc -O1 -S -emit-llvm -o /tmp/repro.ll</div><div>$ bin/clang -c /tmp/repro.ll -O2 -o /tmp/repro.o # hangs</div><div><br></div><div>; ModuleID = '/tmp/repro.cc'<br>source_filename = "/tmp/repro.cc"<br>target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"<br>target triple = "x86_64-unknown-linux-gnu"<br><br>%class.D = type { i64 }<br>%class.a = type { %class.g }<br>%class.g = type { i32*, i32* }<br><br>$_ZNK1aIliEixEl = comdat any<br><br>$_ZNK1aIliE1jEv = comdat any<br><br>@o = dso_local local_unnamed_addr global i32 0, align 4<br>@p = dso_local local_unnamed_addr global i32 0, align 4<br>@.str = private unnamed_addr constant [1 x i8] zeroinitializer, align 1<br><br>; Function Attrs: uwtable mustprogress<br>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 {<br> %3 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) %1, i64 0) #3<br> %4 = icmp eq i64 %3, 0<br> br i1 %4, label %26, label %5<br><br>5: ; preds = %2<br> %6 = call i64 @_ZNK1aIliE1jEv(%class.a* nonnull dereferenceable(16) %1)<br> %7 = icmp eq i64 %6, 0<br> br i1 %7, label %26, label %8<br><br>8: ; preds = %5<br> %9 = getelementptr inbounds %class.D, %class.D* %0, i64 0, i32 0<br> br label %10<br><br>10: ; preds = %8, %18<br> %11 = phi i64 [ 0, %8 ], [ %23, %18 ]<br> %12 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) %1, i64 %11) #3<br> %13 = icmp eq i64 %12, 0<br> br i1 %13, label %18, label %14<br><br>14: ; preds = %10, %14<br> %15 = load i32, i32* @o, align 4, !tbaa !2<br> %16 = call i32 @_Z3fn1IiiEiT_T0_PKc(i32 %15, i32 0, i8* getelementptr inbounds ([1 x i8], [1 x i8]* @.str, i64 0, i64 0))<br> %17 = icmp eq i32 %16, 0<br> br i1 %17, label %18, label %14, !llvm.loop !6<br><br>18: ; preds = %14, %10<br> %19 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) %1, i64 %11) #3<br> %20 = load i32, i32* @p, align 4, !tbaa !2<br> %21 = sext i32 %20 to i64<br> %22 = sdiv i64 %19, %21<br> store i64 %22, i64* %9, align 8, !tbaa !9<br> %23 = add i64 %11, 1<br> %24 = call i64 @_ZNK1aIliE1jEv(%class.a* nonnull dereferenceable(16) %1)<br> %25 = icmp eq i64 %24, 0<br> br i1 %25, label %26, label %10, !llvm.loop !12<br><br>26: ; preds = %18, %5, %2<br> ret void<br>}<br><br>; Function Attrs: nounwind uwtable willreturn mustprogress<br>define linkonce_odr dso_local i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) %0, i64 %1) local_unnamed_addr #1 comdat align 2 {<br> %3 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 0<br> %4 = load i32*, i32** %3, align 8, !tbaa !13<br> %5 = getelementptr inbounds i32, i32* %4, i64 %1<br> %6 = load i32, i32* %5, align 4, !tbaa !2<br> %7 = sext i32 %6 to i64<br> ret i64 %7<br>}<br><br>; Function Attrs: nounwind uwtable willreturn mustprogress<br>define linkonce_odr dso_local i64 @_ZNK1aIliE1jEv(%class.a* nonnull dereferenceable(16) %0) local_unnamed_addr #1 comdat align 2 {<br> %2 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 1<br> %3 = load i32*, i32** %2, align 8, !tbaa !16<br> %4 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 0<br> %5 = load i32*, i32** %4, align 8, !tbaa !13<br> %6 = ptrtoint i32* %3 to i64<br> %7 = ptrtoint i32* %5 to i64<br> %8 = sub i64 %6, %7<br> %9 = ashr exact i64 %8, 2<br> ret i64 %9<br>}<br><br>declare dso_local i32 @_Z3fn1IiiEiT_T0_PKc(i32, i32, i8*) local_unnamed_addr #2<br><br>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" }<br>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" }<br>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" }<br>attributes #3 = { nounwind }<br><br>!llvm.module.flags = !{!0}<br>!llvm.ident = !{!1}<br><br>!0 = !{i32 1, !"wchar_size", i32 4}<br>!1 = !{!"clang version 13.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a> dfd27ebbd0eb137c9a439b7c537bb87ba903efd3)"}<br>!2 = !{!3, !3, i64 0}<br>!3 = !{!"int", !4, i64 0}<br>!4 = !{!"omnipotent char", !5, i64 0}<br>!5 = !{!"Simple C++ TBAA"}<br>!6 = distinct !{!6, !7, !8}<br>!7 = !{!"llvm.loop.mustprogress"}<br>!8 = !{!"llvm.loop.unroll.disable"}<br>!9 = !{!10, !11, i64 0}<br>!10 = !{!"_ZTS1D", !11, i64 0}<br>!11 = !{!"long", !4, i64 0}<br>!12 = distinct !{!12, !7, !8}<br>!13 = !{!14, !15, i64 0}<br>!14 = !{!"_ZTS1g", !15, i64 0, !15, i64 8}<br>!15 = !{!"any pointer", !4, i64 0}<br></div><div>!16 = !{!14, !15, i64 8}</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><p>
</p>
<div>On 3/12/21 1:59 PM, Jordan Rupprecht
via llvm-commits wrote:<br>
</div>
<blockquote type="cite">
<pre>Author: Jordan Rupprecht
Date: 2021-03-12T13:59:14-08:00
New Revision: 8d20f2c2c66eb486ff23cc3d55a53bd840b36971
URL: <a href="https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971" target="_blank" class="cremed">https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971</a>
DIFF: <a href="https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971.diff" target="_blank" class="cremed">https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971.diff</a>
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"
-
-@b = dso_local local_unnamed_addr global i64 0, align 8
-@c = dso_local local_unnamed_addr global i64 0, align 8
-@d = dso_local local_unnamed_addr global i64 0, align 8
-@e = dso_local local_unnamed_addr global i64 0, align 8
-@f = dso_local local_unnamed_addr global i64 0, align 8
-@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
-}
_______________________________________________
llvm-commits mailing list
<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>
<a href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits" target="_blank" class="cremed">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits</a>
</pre>
</blockquote>
</div>
</blockquote></div></div>