[llvm] r245588 - Fix a debug location handling bug in GVN.
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 20 12:16:16 PDT 2015
On Thu, Aug 20, 2015 at 11:42 AM, Adrian Prantl <aprantl at apple.com> wrote:
>
> On Aug 20, 2015, at 11:36 AM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
>
> On Thu, Aug 20, 2015 at 11:28 AM, Adrian Prantl via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>>
>> > On Aug 20, 2015, at 11:23 AM, Adrian Prantl via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>> >
>> > Author: adrian
>> > Date: Thu Aug 20 13:23:56 2015
>> > New Revision: 245588
>> >
>> > URL:
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D245588-26view-3Drev&d=BQIGaQ&c=eEvniauFctOgLOKGJOplqw&r=cTx6f1tAfqPeajYunFWp7_8ot79RnHyNteqzig4fXmA&m=1OMFcIVXCQ-3a2cHjkzeoWw-2B9l6GXi6522rq-fXRo&s=UsPyOZjvOF75FKD4kBH1X1gMSZIq-pFRDC8kvWBS2w0&e=
>> > 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:
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_llvm_trunk_lib_Transforms_Scalar_GVN.cpp-3Frev-3D245588-26r1-3D245587-26r2-3D245588-26view-3Ddiff&d=BQIGaQ&c=eEvniauFctOgLOKGJOplqw&r=cTx6f1tAfqPeajYunFWp7_8ot79RnHyNteqzig4fXmA&m=1OMFcIVXCQ-3a2cHjkzeoWw-2B9l6GXi6522rq-fXRo&s=qxyWSdB0E7E3fhM6zkYTzydfTcgVPfVFpm85bvbqaw0&e=
>> >
>> ==============================================================================
>> > --- 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:
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_llvm_trunk_test_DebugInfo_gvn.ll-3Frev-3D245588-26view-3Dauto&d=BQIGaQ&c=eEvniauFctOgLOKGJOplqw&r=cTx6f1tAfqPeajYunFWp7_8ot79RnHyNteqzig4fXmA&m=1OMFcIVXCQ-3a2cHjkzeoWw-2B9l6GXi6522rq-fXRo&s=Zg7ORbK0TOC9ZrZ1W5nHutgFgc5wAHA6RlagiMt6NAc&e=
>> >
>> ==============================================================================
>> > --- 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.
>>
>> ... which has been fixed in r245589.
>>
>
> Ideally we'd have a reproduction that was from IR that wasn't produced by
> a bug in another pass - but if that's not easy to come by, this is still
> legit, for sure (we shouldn't crash on any IR input, really - which does
> sort of make that assertion a bit dodgy,
>
>
> Not really, Duncan (I think?) added a verifier check to the same effect as
> the assertion recently, so it is no longer legal to have wrong debug
> locations. “No debug locations” is more of a gray area of course.
>
Right, the constraint here is somewhat unverifiable (not entirely, but it's
involved). I tried to make stronger constraints but there were use cases in
the way:
1) it's not every call in a debug-having function without a debug location,
we produce some calls that are never inline candidates and have no logical
location (I seem to recall... but I forget what they are - you'd think
everything would have a location?)
2) It's not every call /to/ a debug-having function without a debug
location - debug-having functions may be called from non-debug having
functions just fine (& even inlined across that boundary - so long as if
the caller is inlined into its caller, if that caller has debug info then
the call must have a location, etc... - which could be many levels removed
through multiple non-debug functions)
So it's specifically only when inlining is possible and there is a chain of
inlinable calls that leads to some debug-having instructions (even when the
intermediate calls may not have debug info themselves) from a debug-having
function... then it's a problem.
>
> but at least it expresses a relatively limited constraint which this IR
> file satisfies, even with this missing location)
>
>
>>
>> > + %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
>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.dbg.cu&d=BQMFaQ&c=eEvniauFctOgLOKGJOplqw&r=cTx6f1tAfqPeajYunFWp7_8ot79RnHyNteqzig4fXmA&m=tCvabjHLRgtE8pYEwk_4rnKJHHe7ViXrRrU8PtnORI0&s=lRfYUH6akjutgNevAQG4U-M5kYf6yT8W4Lb1_BbJlyw&e=>
>> = !{!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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