[llvm] r340583 - DebugInfo: Improve debug location merging
Adrian Prantl via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 24 15:05:11 PDT 2018
Unfortunately I don't have a reduced testcase yet, but basically what happens is that
!1 = !DISubprogram(..., file: !0)
!2 = !DISubprogram(..., file: !0)
LocA = !DILocation(line: 1, scope: DISubprogram !1, inlinedAt: !3)
LocB = !DILocation(line: 2, scope: DISubprogram !2, inlinedAt: !3)
and getMergedLocation(LocA, LocB) returns !DILocation(line: 0, scope: !0, inlinedAt: !3), which is invalid.
Lacking a better testcase, I guess we could easily add a unit test for that scenario.
-- adrian
> On Aug 24, 2018, at 1:47 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
> No worries - always appreciate the follow-up! Happy to help if it turns out there's anything I can.
>
> On Fri, Aug 24, 2018 at 1:17 PM Adrian Prantl <aprantl at apple.com <mailto:aprantl at apple.com>> wrote:
> Yeah, the Verifier doesn't verify that the scope of a DILocation is a DILocalScope. I'll start there!
>
> sorry for the noise.
> -- adrian
>
> > On Aug 24, 2018, at 1:12 PM, Adrian Prantl <aprantl at apple.com <mailto:aprantl at apple.com>> wrote:
> >
> > There'a also a >50% chance that this just exposed a bug in the Swift frontend; all reproducers I've got so far are Swift code.
> >
> > -- adrian
> >
> >> On Aug 24, 2018, at 1:10 PM, Adrian Prantl <aprantl at apple.com <mailto:aprantl at apple.com>> wrote:
> >>
> >> I think this commit may be to cause for some failures we are seeing on our internal bots.
> >> They are hitting an assertion in llvm::DILocation::getMergedLocation(llvm::DILocation const*, llvm::DILocation const*) at
> >> DIScope *S = LocA->getScope()
> >> because the scope of LocA is a DIFile (which is not a valid DILocalScope).
> >>
> >> I'll post an update once I know more.
> >>
> >> -- adrian
> >>
> >>> On Aug 23, 2018, at 3:35 PM, David Blaikie via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
> >>>
> >>> Author: dblaikie
> >>> Date: Thu Aug 23 15:35:58 2018
> >>> New Revision: 340583
> >>>
> >>> URL: http://llvm.org/viewvc/llvm-project?rev=340583&view=rev <http://llvm.org/viewvc/llvm-project?rev=340583&view=rev>
> >>> Log:
> >>> DebugInfo: Improve debug location merging
> >>>
> >>> Fix a set of related bugs:
> >>>
> >>> * Considering two locations as equivalent when their lines are the same
> >>> but their scopes are different causes erroneous debug info that
> >>> attributes a commoned call to be attributed to one of the two calls it
> >>> was commoned from.
> >>>
> >>> * The previous code to compute a new location's scope was inaccurate and
> >>> would use the inlinedAt that was the /parent/ of the inlinedAt that is
> >>> the nearest common one, and also used that parent scope instead of the
> >>> nearest common scope.
> >>>
> >>> * Not generating new locations generally seemed like a lower quality
> >>> choice
> >>>
> >>> There was some risk that generating more new locations could hurt object
> >>> size by making more fine grained line table entries, but it looks like
> >>> that was offset by the decrease in line table (& address & ranges) size
> >>> caused by more accurately computing the scope - which likely lead to
> >>> fewer range entries (more contiguous ranges) & reduced size that way.
> >>>
> >>> All up with these changes I saw minor reductions (-1.21%, -1.77%) in
> >>> .rela.debug_ranges and .rela.debug_addr (in a fission, compressed debug
> >>> info build) as well as other minor size changes (generally reductinos)
> >>> across the board (-1.32% debug_info.dwo, -1.28% debug_loc.dwo). Measured
> >>> in an optimized (-O2) build of the clang binary.
> >>>
> >>> If you are investigating a size regression in an optimized debug builds,
> >>> this is certainly a patch to look into - and I'd be happy to look into
> >>> any major regressions found & see what we can do to address them.
> >>>
> >>> Added:
> >>> llvm/trunk/test/DebugInfo/X86/merge_inlined_loc.ll
> >>> Modified:
> >>> llvm/trunk/include/llvm/IR/DebugInfoMetadata.h
> >>> llvm/trunk/lib/IR/DebugInfo.cpp
> >>> llvm/trunk/lib/IR/DebugInfoMetadata.cpp
> >>> llvm/trunk/test/DebugInfo/COFF/local-variables.ll
> >>>
> >>> Modified: llvm/trunk/include/llvm/IR/DebugInfoMetadata.h
> >>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/DebugInfoMetadata.h?rev=340583&r1=340582&r2=340583&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/DebugInfoMetadata.h?rev=340583&r1=340582&r2=340583&view=diff>
> >>> ==============================================================================
> >>> --- llvm/trunk/include/llvm/IR/DebugInfoMetadata.h (original)
> >>> +++ llvm/trunk/include/llvm/IR/DebugInfoMetadata.h Thu Aug 23 15:35:58 2018
> >>> @@ -1479,19 +1479,6 @@ public:
> >>> return getScope();
> >>> }
> >>>
> >>> - /// Check whether this can be discriminated from another location.
> >>> - ///
> >>> - /// Check \c this can be discriminated from \c RHS in a linetable entry.
> >>> - /// Scope and inlined-at chains are not recorded in the linetable, so they
> >>> - /// cannot be used to distinguish basic blocks.
> >>> - bool canDiscriminate(const DILocation &RHS) const {
> >>> - return getLine() != RHS.getLine() ||
> >>> - getColumn() != RHS.getColumn() ||
> >>> - getDiscriminator() != RHS.getDiscriminator() ||
> >>> - getFilename() != RHS.getFilename() ||
> >>> - getDirectory() != RHS.getDirectory();
> >>> - }
> >>> -
> >>> /// Get the DWARF discriminator.
> >>> ///
> >>> /// DWARF discriminators distinguish identical file locations between
> >>> @@ -1539,8 +1526,6 @@ public:
> >>> /// discriminator.
> >>> inline const DILocation *cloneWithDuplicationFactor(unsigned DF) const;
> >>>
> >>> - enum { NoGeneratedLocation = false, WithGeneratedLocation = true };
> >>> -
> >>> /// When two instructions are combined into a single instruction we also
> >>> /// need to combine the original locations into a single location.
> >>> ///
> >>> @@ -1555,9 +1540,8 @@ public:
> >>> ///
> >>> /// \p GenerateLocation: Whether the merged location can be generated when
> >>> /// \p LocA and \p LocB differ.
> >>> - static const DILocation *
> >>> - getMergedLocation(const DILocation *LocA, const DILocation *LocB,
> >>> - bool GenerateLocation = NoGeneratedLocation);
> >>> + static const DILocation *getMergedLocation(const DILocation *LocA,
> >>> + const DILocation *LocB);
> >>>
> >>> /// Returns the base discriminator for a given encoded discriminator \p D.
> >>> static unsigned getBaseDiscriminatorFromDiscriminator(unsigned D) {
> >>>
> >>> Modified: llvm/trunk/lib/IR/DebugInfo.cpp
> >>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DebugInfo.cpp?rev=340583&r1=340582&r2=340583&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DebugInfo.cpp?rev=340583&r1=340582&r2=340583&view=diff>
> >>> ==============================================================================
> >>> --- llvm/trunk/lib/IR/DebugInfo.cpp (original)
> >>> +++ llvm/trunk/lib/IR/DebugInfo.cpp Thu Aug 23 15:35:58 2018
> >>> @@ -690,8 +690,7 @@ unsigned llvm::getDebugMetadataVersionFr
> >>>
> >>> void Instruction::applyMergedLocation(const DILocation *LocA,
> >>> const DILocation *LocB) {
> >>> - setDebugLoc(DILocation::getMergedLocation(LocA, LocB,
> >>> - DILocation::WithGeneratedLocation));
> >>> + setDebugLoc(DILocation::getMergedLocation(LocA, LocB));
> >>> }
> >>>
> >>> //===----------------------------------------------------------------------===//
> >>>
> >>> Modified: llvm/trunk/lib/IR/DebugInfoMetadata.cpp
> >>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DebugInfoMetadata.cpp?rev=340583&r1=340582&r2=340583&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DebugInfoMetadata.cpp?rev=340583&r1=340582&r2=340583&view=diff>
> >>> ==============================================================================
> >>> --- llvm/trunk/lib/IR/DebugInfoMetadata.cpp (original)
> >>> +++ llvm/trunk/lib/IR/DebugInfoMetadata.cpp Thu Aug 23 15:35:58 2018
> >>> @@ -14,7 +14,7 @@
> >>> #include "llvm/IR/DebugInfoMetadata.h"
> >>> #include "LLVMContextImpl.h"
> >>> #include "MetadataImpl.h"
> >>> -#include "llvm/ADT/SmallPtrSet.h"
> >>> +#include "llvm/ADT/SmallSet.h"
> >>> #include "llvm/ADT/StringSwitch.h"
> >>> #include "llvm/IR/DIBuilder.h"
> >>> #include "llvm/IR/Function.h"
> >>> @@ -69,28 +69,40 @@ DILocation *DILocation::getImpl(LLVMCont
> >>> }
> >>>
> >>> const DILocation *DILocation::getMergedLocation(const DILocation *LocA,
> >>> - const DILocation *LocB,
> >>> - bool GenerateLocation) {
> >>> + const DILocation *LocB) {
> >>> if (!LocA || !LocB)
> >>> return nullptr;
> >>>
> >>> - if (LocA == LocB || !LocA->canDiscriminate(*LocB))
> >>> + if (LocA == LocB)
> >>> return LocA;
> >>>
> >>> - if (!GenerateLocation)
> >>> - return nullptr;
> >>> -
> >>> SmallPtrSet<DILocation *, 5> InlinedLocationsA;
> >>> for (DILocation *L = LocA->getInlinedAt(); L; L = L->getInlinedAt())
> >>> InlinedLocationsA.insert(L);
> >>> + SmallSet<std::pair<DIScope *, DILocation *>, 5> Locations;
> >>> + DIScope *S = LocA->getScope();
> >>> + DILocation *L = LocA->getInlinedAt();
> >>> + while (S) {
> >>> + Locations.insert(std::make_pair(S, L));
> >>> + S = S->getScope().resolve();
> >>> + if (!S && L) {
> >>> + S = L->getScope();
> >>> + L = L->getInlinedAt();
> >>> + }
> >>> + }
> >>> const DILocation *Result = LocB;
> >>> - for (DILocation *L = LocB->getInlinedAt(); L; L = L->getInlinedAt()) {
> >>> - Result = L;
> >>> - if (InlinedLocationsA.count(L))
> >>> + S = LocB->getScope();
> >>> + L = LocB->getInlinedAt();
> >>> + while (S) {
> >>> + if (Locations.count(std::make_pair(S, L)))
> >>> break;
> >>> + S = S->getScope().resolve();
> >>> + if (!S && L) {
> >>> + S = L->getScope();
> >>> + L = L->getInlinedAt();
> >>> + }
> >>> }
> >>> - return DILocation::get(Result->getContext(), 0, 0, Result->getScope(),
> >>> - Result->getInlinedAt());
> >>> + return DILocation::get(Result->getContext(), 0, 0, S, L);
> >>> }
> >>>
> >>> DINode::DIFlags DINode::getFlag(StringRef Flag) {
> >>>
> >>> Modified: llvm/trunk/test/DebugInfo/COFF/local-variables.ll
> >>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/COFF/local-variables.ll?rev=340583&r1=340582&r2=340583&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/COFF/local-variables.ll?rev=340583&r1=340582&r2=340583&view=diff>
> >>> ==============================================================================
> >>> --- llvm/trunk/test/DebugInfo/COFF/local-variables.ll (original)
> >>> +++ llvm/trunk/test/DebugInfo/COFF/local-variables.ll Thu Aug 23 15:35:58 2018
> >>> @@ -60,7 +60,7 @@
> >>> ; ASM: leaq 36(%rsp), %rcx
> >>> ; ASM: [[else_end:\.Ltmp.*]]:
> >>> ; ASM: .LBB0_3: # %if.end
> >>> -; ASM: .cv_loc 0 1 17 1 # t.cpp:17:1
> >>> +; ASM: .cv_loc 0 1 0 0 # t.cpp:0:0
> >>> ; ASM: callq capture
> >>> ; ASM: nop
> >>> ; ASM: addq $56, %rsp
> >>>
> >>> Added: llvm/trunk/test/DebugInfo/X86/merge_inlined_loc.ll
> >>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/merge_inlined_loc.ll?rev=340583&view=auto <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/merge_inlined_loc.ll?rev=340583&view=auto>
> >>> ==============================================================================
> >>> --- llvm/trunk/test/DebugInfo/X86/merge_inlined_loc.ll (added)
> >>> +++ llvm/trunk/test/DebugInfo/X86/merge_inlined_loc.ll Thu Aug 23 15:35:58 2018
> >>> @@ -0,0 +1,100 @@
> >>> +; RUN: llc %s -mtriple=x86_64-unknown-unknown -o - | FileCheck %s
> >>> +
> >>> +; Generated with "clang -g -c -emit-llvm -S -O3"
> >>> +
> >>> +; This will test several features of merging debug locations. Importantly,
> >>> +; locations with the same source line but different scopes should be merged to
> >>> +; a line zero location at the nearest common scope and inlining. The location
> >>> +; of the single call to "common" (the two calls are collapsed together by
> >>> +; BranchFolding) should be attributed to line zero inside the wrapper2 inlined
> >>> +; scope within f1.
> >>> +
> >>> +; void common();
> >>> +; inline void wrapper() { common(); }
> >>> +; extern bool b;
> >>> +; void sink();
> >>> +; inline void wrapper2() {
> >>> +; if (b) {
> >>> +; sink();
> >>> +; wrapper();
> >>> +; } else
> >>> +; wrapper();
> >>> +; }
> >>> +; void f1() { wrapper2(); }
> >>> +
> >>> +; Ensure there is only one inlined_subroutine (for wrapper2, none for wrapper)
> >>> +; & that its address range includes the call to 'common'.
> >>> +
> >>> +; CHECK: jmp _Z6commonv
> >>> +; CHECK-NEXT: [[LABEL:.*]]:
> >>> +
> >>> +; CHECK: .section .debug_info
> >>> +; CHECK: DW_TAG_subprogram
> >>> +; CHECK: DW_TAG_subprogram
> >>> +; CHECK-NOT: {{DW_TAG\|End Of Children}}
> >>> +; CHECK: DW_TAG_inlined_subroutine
> >>> +; CHECK-NOT: {{DW_TAG\|End Of Children}}
> >>> +; CHECK: [[LABEL]]-{{.*}} DW_AT_high_pc
> >>> +; CHECK-NOT: DW_TAG
> >>> +
> >>> +
> >>> +
> >>> + at b = external dso_local local_unnamed_addr global i8, align 1
> >>> +
> >>> +; Function Attrs: uwtable
> >>> +define dso_local void @_Z2f1v() local_unnamed_addr !dbg !7 {
> >>> +entry:
> >>> + %0 = load i8, i8* @b, align 1, !dbg !10, !tbaa !14, !range !18
> >>> + %tobool.i = icmp eq i8 %0, 0, !dbg !10
> >>> + br i1 %tobool.i, label %if.else.i, label %if.then.i, !dbg !19
> >>> +
> >>> +if.then.i: ; preds = %entry
> >>> + tail call void @_Z4sinkv(), !dbg !20
> >>> + tail call void @_Z6commonv(), !dbg !22
> >>> + br label %_Z8wrapper2v.exit, !dbg !25
> >>> +
> >>> +if.else.i: ; preds = %entry
> >>> + tail call void @_Z6commonv(), !dbg !26
> >>> + br label %_Z8wrapper2v.exit
> >>> +
> >>> +_Z8wrapper2v.exit: ; preds = %if.then.i, %if.else.i
> >>> + ret void, !dbg !28
> >>> +}
> >>> +
> >>> +declare dso_local void @_Z4sinkv() local_unnamed_addr
> >>> +
> >>> +declare dso_local void @_Z6commonv() local_unnamed_addr
> >>> +
> >>> +!llvm.dbg.cu <http://llvm.dbg.cu/> = !{!0}
> >>> +!llvm.module.flags = !{!3, !4, !5}
> >>> +!llvm.ident = !{!6}
> >>> +
> >>> +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 8.0.0 (trunk 340559) (llvm/trunk 340572)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
> >>> +!1 = !DIFile(filename: "merge_loc.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
> >>> +!2 = !{}
> >>> +!3 = !{i32 2, !"Dwarf Version", i32 4}
> >>> +!4 = !{i32 2, !"Debug Info Version", i32 3}
> >>> +!5 = !{i32 1, !"wchar_size", i32 4}
> >>> +!6 = !{!"clang version 8.0.0 (trunk 340559) (llvm/trunk 340572)"}
> >>> +!7 = distinct !DISubprogram(name: "f1", linkageName: "_Z2f1v", scope: !1, file: !1, line: 12, type: !8, isLocal: false, isDefinition: true, scopeLine: 12, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !2)
> >>> +!8 = !DISubroutineType(types: !9)
> >>> +!9 = !{null}
> >>> +!10 = !DILocation(line: 6, column: 7, scope: !11, inlinedAt: !13)
> >>> +!11 = distinct !DILexicalBlock(scope: !12, file: !1, line: 6, column: 7)
> >>> +!12 = distinct !DISubprogram(name: "wrapper2", linkageName: "_Z8wrapper2v", scope: !1, file: !1, line: 5, type: !8, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !2)
> >>> +!13 = distinct !DILocation(line: 13, column: 3, scope: !7)
> >>> +!14 = !{!15, !15, i64 0}
> >>> +!15 = !{!"bool", !16, i64 0}
> >>> +!16 = !{!"omnipotent char", !17, i64 0}
> >>> +!17 = !{!"Simple C++ TBAA"}
> >>> +!18 = !{i8 0, i8 2}
> >>> +!19 = !DILocation(line: 6, column: 7, scope: !12, inlinedAt: !13)
> >>> +!20 = !DILocation(line: 7, column: 5, scope: !21, inlinedAt: !13)
> >>> +!21 = distinct !DILexicalBlock(scope: !11, file: !1, line: 6, column: 10)
> >>> +!22 = !DILocation(line: 2, column: 25, scope: !23, inlinedAt: !24)
> >>> +!23 = distinct !DISubprogram(name: "wrapper", linkageName: "_Z7wrapperv", scope: !1, file: !1, line: 2, type: !8, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !2)
> >>> +!24 = distinct !DILocation(line: 8, column: 5, scope: !21, inlinedAt: !13)
> >>> +!25 = !DILocation(line: 9, column: 3, scope: !21, inlinedAt: !13)
> >>> +!26 = !DILocation(line: 2, column: 25, scope: !23, inlinedAt: !27)
> >>> +!27 = distinct !DILocation(line: 10, column: 5, scope: !11, inlinedAt: !13)
> >>> +!28 = !DILocation(line: 14, column: 1, scope: !7)
> >>>
> >>>
> >>> _______________________________________________
> >>> llvm-commits mailing list
> >>> llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>
> >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits>
> >>
> >
>
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