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

Tue Nov 17 07:27:15 PST 2015

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.

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)
>> > >
>> > >