[llvm] r245588 - Fix a debug location handling bug in GVN.

Tom Stellard via llvm-commits llvm-commits at lists.llvm.org
Tue Nov 17 08:23:56 PST 2015 

On Tue, Nov 17, 2015 at 04:27:15PM +0100, Björn Steinbrink wrote:
> Sorry for the late reply, I had assumed that the patch would go into
> 3.7.1 and only just noticed that it has not been merged. My thinking
> that it was a regression was based on the fact that I didn't see the
> problem with 3.6. Thinking about it again, it might also have been the
> case that the optimizations differ slightly so we just didn't trigger
> it.
> 

Hi,

This was my fault, I overlooked this patch.  We've already tagged -rc1,
if we don another -rc, then we can get this into 3.7.1 otherwise, it will
have to wait until 3.7.2.

-Tom

> 2015-11-09 23:51 GMT+01:00 Eric Christopher <echristo at gmail.com>:
> > I'm really not sure how it could be a regression, but I'm also not against
> > having it in the branch.
> >
> > -eric
> >
> > On Fri, Nov 6, 2015 at 6:20 AM Tom Stellard <tom at stellard.net> wrote:
> >>
> >> Hi Eric,
> >>
> >> Is this patch OK for the 3.7 branch?
> >>
> >> Thanks,
> >> Tom
> >>
> >> On Fri, Nov 06, 2015 at 02:35:51PM +0100, Björn Steinbrink wrote:
> >> > Hi,
> >> >
> >> > can we get this into 3.7.1? The bug that is fixed here is a regression
> >> > from 3.6 and bootstrapping Rust with debug info enabled triggers this
> >> > bug, so we currently can't build with debug info enabled with an
> >> > upstream 3.7 release which is unfortunate.
> >> >
> >> > Thanks,
> >> > Björn
> >> >
> >> > On 2015.08.20 18:23:57 -0000, Adrian Prantl via llvm-commits wrote:
> >> > > Author: adrian
> >> > > Date: Thu Aug 20 13:23:56 2015
> >> > > New Revision: 245588
> >> > >
> >> > > URL: http://llvm.org/viewvc/llvm-project?rev=245588&view=rev
> >> > > Log:
> >> > > Fix a debug location handling bug in GVN.
> >> > > Caught by the famous "DebugLoc describes the currect SubProgram"
> >> > > assertion.
> >> > >
> >> > > When GVN is removing a nonlocal load it updates the debug location of
> >> > > the
> >> > > SSA value it replaced the load with with the one of the load. In the
> >> > > testcase this actually overwrites a valid debug location with an empty
> >> > > one.
> >> > >
> >> > > In reality GVN has to make an arbitrary choice between two equally
> >> > > valid
> >> > > debug locations. This patch changes to behavior to only update the
> >> > > location if the value doesn't already have a debug location.
> >> > >
> >> > > Added:
> >> > >     llvm/trunk/test/DebugInfo/gvn.ll
> >> > > Modified:
> >> > >     llvm/trunk/lib/Transforms/Scalar/GVN.cpp
> >> > >
> >> > > Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp
> >> > > URL:
> >> > > http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=245588&r1=245587&r2=245588&view=diff
> >> > >
> >> > > ==============================================================================
> >> > > --- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)
> >> > > +++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Thu Aug 20 13:23:56 2015
> >> > > @@ -1744,7 +1744,8 @@ bool GVN::processNonLocalLoad(LoadInst *
> >> > >      if (isa<PHINode>(V))
> >> > >        V->takeName(LI);
> >> > >      if (Instruction *I = dyn_cast<Instruction>(V))
> >> > > -      I->setDebugLoc(LI->getDebugLoc());
> >> > > +      if (LI->getDebugLoc())
> >> > > +        I->setDebugLoc(LI->getDebugLoc());
> >> > >      if (V->getType()->getScalarType()->isPointerTy())
> >> > >        MD->invalidateCachedPointerInfo(V);
> >> > >      markInstructionForDeletion(LI);
> >> > >
> >> > > Added: llvm/trunk/test/DebugInfo/gvn.ll
> >> > > URL:
> >> > > http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/gvn.ll?rev=245588&view=auto
> >> > >
> >> > > ==============================================================================
> >> > > --- llvm/trunk/test/DebugInfo/gvn.ll (added)
> >> > > +++ llvm/trunk/test/DebugInfo/gvn.ll Thu Aug 20 13:23:56 2015
> >> > > @@ -0,0 +1,135 @@
> >> > > +; RUN: opt < %s -O2 -gvn -S | FileCheck %s
> >> > > +;
> >> > > +; Produced at -O2 from:
> >> > > +; struct context {
> >> > > +;   int cur_pid
> >> > > +; };
> >> > > +; int a, b, c, f, d;
> >> > > +; int pid_for_task(int);
> >> > > +; sample(struct context *p1)
> >> > > +; {
> >> > > +;   if (c)
> >> > > +;     b = a;
> >> > > +;   if (a && p1->cur_pid)
> >> > > +;     sample_internal();
> >> > > +; }
> >> > > +; callback() {
> >> > > +;   f = pid_for_task(d);
> >> > > +;   sample(&f);
> >> > > +; }
> >> > > +
> >> > > +target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
> >> > > +target triple = "arm64-apple-ios"
> >> > > +
> >> > > +%struct.context = type { i32 }
> >> > > +
> >> > > + at c = common global i32 0, align 4
> >> > > + at a = common global i32 0, align 4
> >> > > + at b = common global i32 0, align 4
> >> > > + at d = common global i32 0, align 4
> >> > > + at f = common global i32 0, align 4
> >> > > +
> >> > > +; Function Attrs: nounwind
> >> > > +declare i32 @sample_internal(...)
> >> > > +
> >> > > +; Function Attrs: nounwind
> >> > > +define i32 @callback() #0 {
> >> > > +entry:
> >> > > +  %0 = load i32, i32* @d, align 4, !dbg !37
> >> > > +
> >> > > +  ; Verify that the call still has a debug location after GVN.
> >> > > +  ; CHECK: %call = tail call i32 @pid_for_task(i32 %0) #{{[0-9]}},
> >> > > !dbg
> >> > > +  %call = tail call i32 @pid_for_task(i32 %0) #3, !dbg !37
> >> > > +
> >> > > +  store i32 %call, i32* @f, align 4, !dbg !37
> >> > > +  tail call void @llvm.dbg.value(metadata %struct.context* bitcast
> >> > > (i32* @f to %struct.context*), i64 0, metadata !25, metadata !26) #3, !dbg
> >> > > !38
> >> > > +  %1 = load i32, i32* @c, align 4, !dbg !40
> >> > > +  %tobool.i = icmp eq i32 %1, 0, !dbg !40
> >> > > +  %.pr.i = load i32, i32* @a, align 4, !dbg !41
> >> > > +  br i1 %tobool.i, label %if.end.i, label %if.then.i, !dbg !42
> >> > > +
> >> > > +if.then.i:                                        ; preds = %entry
> >> > > +  store i32 %.pr.i, i32* @b, align 4, !dbg !43
> >> > > +  br label %if.end.i, !dbg !43
> >> > > +
> >> > > +if.end.i:                                         ; preds =
> >> > > %if.then.i, %entry
> >> > > +  %tobool1.i = icmp eq i32 %.pr.i, 0, !dbg !41
> >> > > +
> >> > > +  ; This instruction has no debug location -- in this
> >> > > +  ; particular case it was removed by a bug in SimplifyCFG.
> >> > > +  %2 = load i32, i32* @f, align 4
> >> > > +
> >> > > +  ; GVN is supposed to replace the load of @f with a direct reference
> >> > > to %call.
> >> > > +  ; CHECK: %tobool2.i = icmp eq i32 %call, 0, !dbg
> >> > > +  %tobool2.i = icmp eq i32 %2, 0, !dbg !41
> >> > > +
> >> > > +  %or.cond = or i1 %tobool1.i, %tobool2.i, !dbg !41
> >> > > +  br i1 %or.cond, label %sample.exit, label %if.then.3.i, !dbg !41
> >> > > +
> >> > > +if.then.3.i:                                      ; preds = %if.end.i
> >> > > +  %call.i = tail call i32 bitcast (i32 (...)* @sample_internal to i32
> >> > > ()*)() #3, !dbg !44
> >> > > +  br label %sample.exit, !dbg !44
> >> > > +
> >> > > +sample.exit:                                      ; preds =
> >> > > %if.end.i, %if.then.3.i
> >> > > +  ret i32 undef, !dbg !45
> >> > > +}
> >> > > +
> >> > > +declare i32 @pid_for_task(i32) #1
> >> > > +
> >> > > +; Function Attrs: nounwind readnone
> >> > > +declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #2
> >> > > +
> >> > > +attributes #0 = { nounwind }
> >> > > +attributes #2 = { nounwind readnone }
> >> > > +attributes #3 = { nounwind }
> >> > > +
> >> > > +!llvm.dbg.cu = !{!0}
> >> > > +!llvm.module.flags = !{!22, !23}
> >> > > +!llvm.ident = !{!24}
> >> > > +
> >> > > +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1,
> >> > > producer: "clang version 3.8.0 (trunk 244473) (llvm/trunk 244644)",
> >> > > isOptimized: false, runtimeVersion: 0, emissionKind: 1, enums: !2,
> >> > > subprograms: !3, globals: !16)
> >> > > +!1 = !DIFile(filename: "test.c", directory: "/")
> >> > > +!2 = !{}
> >> > > +!3 = !{!4, !13}
> >> > > +!4 = !DISubprogram(name: "sample", scope: !5, file: !5, line: 6,
> >> > > type: !6, isLocal: false, isDefinition: true, scopeLine: 7, flags:
> >> > > DIFlagPrototyped, isOptimized: false, variables: !2)
> >> > > +!5 = !DIFile(filename: "test.i", directory: "/")
> >> > > +!6 = !DISubroutineType(types: !7)
> >> > > +!7 = !{!8, !9}
> >> > > +!8 = !DIBasicType(name: "int", size: 32, align: 32, encoding:
> >> > > DW_ATE_signed)
> >> > > +!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size:
> >> > > 64, align: 64)
> >> > > +!10 = !DICompositeType(tag: DW_TAG_structure_type, name: "context",
> >> > > file: !5, line: 1, size: 32, align: 32, elements: !11)
> >> > > +!11 = !{!12}
> >> > > +!12 = !DIDerivedType(tag: DW_TAG_member, name: "cur_pid", scope: !10,
> >> > > file: !5, line: 2, baseType: !8, size: 32, align: 32)
> >> > > +!13 = !DISubprogram(name: "callback", scope: !5, file: !5, line: 13,
> >> > > type: !14, isLocal: false, isDefinition: true, scopeLine: 13, isOptimized:
> >> > > false, function: i32 ()* @callback, variables: !2)
> >> > > +!14 = !DISubroutineType(types: !15)
> >> > > +!15 = !{!8}
> >> > > +!16 = !{!17, !18, !19, !20, !21}
> >> > > +!17 = !DIGlobalVariable(name: "a", scope: !0, file: !5, line: 4,
> >> > > type: !8, isLocal: false, isDefinition: true, variable: i32* @a)
> >> > > +!18 = !DIGlobalVariable(name: "b", scope: !0, file: !5, line: 4,
> >> > > type: !8, isLocal: false, isDefinition: true, variable: i32* @b)
> >> > > +!19 = !DIGlobalVariable(name: "c", scope: !0, file: !5, line: 4,
> >> > > type: !8, isLocal: false, isDefinition: true, variable: i32* @c)
> >> > > +!20 = !DIGlobalVariable(name: "f", scope: !0, file: !5, line: 4,
> >> > > type: !8, isLocal: false, isDefinition: true, variable: i32* @f)
> >> > > +!21 = !DIGlobalVariable(name: "d", scope: !0, file: !5, line: 4,
> >> > > type: !8, isLocal: false, isDefinition: true, variable: i32* @d)
> >> > > +!22 = !{i32 2, !"Dwarf Version", i32 2}
> >> > > +!23 = !{i32 2, !"Debug Info Version", i32 3}
> >> > > +!24 = !{!"clang version 3.8.0 (trunk 244473) (llvm/trunk 244644)"}
> >> > > +!25 = !DILocalVariable(name: "p1", arg: 1, scope: !4, file: !5, line:
> >> > > 6, type: !9)
> >> > > +!26 = !DIExpression()
> >> > > +!27 = !DILocation(line: 6, scope: !4)
> >> > > +!28 = !DILocation(line: 8, scope: !29)
> >> > > +!29 = distinct !DILexicalBlock(scope: !4, file: !5, line: 8)
> >> > > +!30 = !DILocation(line: 10, scope: !31)
> >> > > +!31 = distinct !DILexicalBlock(scope: !4, file: !5, line: 10)
> >> > > +!32 = !DILocation(line: 8, scope: !4)
> >> > > +!33 = !DILocation(line: 9, scope: !29)
> >> > > +!34 = !DILocation(line: 10, scope: !4)
> >> > > +!35 = !DILocation(line: 11, scope: !31)
> >> > > +!36 = !DILocation(line: 12, scope: !4)
> >> > > +!37 = !DILocation(line: 14, scope: !13)
> >> > > +!38 = !DILocation(line: 6, scope: !4, inlinedAt: !39)
> >> > > +!39 = distinct !DILocation(line: 15, scope: !13)
> >> > > +!40 = !DILocation(line: 8, scope: !29, inlinedAt: !39)
> >> > > +!41 = !DILocation(line: 10, scope: !31, inlinedAt: !39)
> >> > > +!42 = !DILocation(line: 8, scope: !4, inlinedAt: !39)
> >> > > +!43 = !DILocation(line: 9, scope: !29, inlinedAt: !39)
> >> > > +!44 = !DILocation(line: 11, scope: !31, inlinedAt: !39)
> >> > > +!45 = !DILocation(line: 16, scope: !13)
> >> > >
> >> > >

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