[llvm] r340583 - DebugInfo: Improve debug location merging
Adrian Prantl via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 24 13:10:03 PDT 2018
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> 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
> 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
> ==============================================================================
> --- 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
> ==============================================================================
> --- 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
> ==============================================================================
> --- 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
> ==============================================================================
> --- 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
> ==============================================================================
> --- 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 = !{!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)
>
>
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