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[XRay][CodeGen] Use the current function symbol as the associated symbol for the instrumentation map

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Summary:
XRay had been assuming that the previous section is the "text" section
of the function when lowering the instrumentation map. Unfortunately
this is not a safe assumption, because we may be coming from lowering
debug type information for the function being lowered.

This fixes an issue with combining -gsplit-dwarf, -generate-type-units,
-debug-compile and -fxray-instrument for sole member functions. When the
split dwarf section is stripped, we're left with references from the
xray_instr_map to the debug section. The change now uses the function's
symbol instead of the previous section's start symbol.

We found the bug while attempting to strip the split debug sections off
an XRay-instrumented object file, which had a peculiar edge-case for
single-function classes where the single function is being lowered.
Because XRay had assocaited the instrumentation map for a function to
the debug types section instead of the function's section, the objcopy
call will fail due to the misplaced reference from the xray_instr_map
section.

Reviewers: pcc, dblaikie, echristo

Subscribers: llvm-commits, aprantl

Differential Revision: https://reviews.llvm.org/D37791

llvm-svn: 313233
This commit is contained in:
Dean Michael Berris 2017-09-14 07:08:23 +00:00
parent e4279bcb0a
commit 9bece8dc4b
5 changed files with 91 additions and 7 deletions
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2
lib/CodeGen/AsmPrinter/AsmPrinter.cpp
View File

@ -2785,7 +2785,7 @@ void AsmPrinter::emitXRayTable() {
MCSection *InstMap = nullptr;
MCSection *FnSledIndex = nullptr;
if (MF->getSubtarget().getTargetTriple().isOSBinFormatELF()) {
auto Associated = dyn_cast<MCSymbolELF>(PrevSection->getBeginSymbol());
auto Associated = dyn_cast<MCSymbolELF>(CurrentFnSym);
assert(Associated != nullptr);
auto Flags = ELF::SHF_WRITE | ELF::SHF_ALLOC | ELF::SHF_LINK_ORDER;
std::string GroupName;

4
test/CodeGen/Mips/xray-section-group.ll
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@ -14,7 +14,7 @@
define i32 @foo() nounwind noinline uwtable "function-instrument"="xray-always" {
; CHECK: .section .text.foo,"ax",@progbits
ret i32 0
; CHECK: .section xray_instr_map,"awo",@progbits,.text.foo,unique,1
; CHECK: .section xray_instr_map,"awo",@progbits,foo,unique,1
}
; CHECK-OBJ: Section {
@ -24,7 +24,7 @@ $bar = comdat any
define i32 @bar() nounwind noinline uwtable "function-instrument"="xray-always" comdat($bar) {
; CHECK: .section .text.bar,"axG",@progbits,bar,comdat
ret i32 1
; CHECK: .section xray_instr_map,"aGwo",@progbits,bar,comdat,.text.bar,unique,2
; CHECK: .section xray_instr_map,"aGwo",@progbits,bar,comdat,bar,unique,2
}
; CHECK-OBJ: Section {

4
test/CodeGen/PowerPC/xray-attribute-instrumentation.ll
View File

@ -22,7 +22,7 @@ define i32 @foo() nounwind noinline uwtable "function-instrument"="xray-always"
; CHECK-NEXT: nop
; CHECK-NEXT: mtlr 0
}
; CHECK-LABEL: xray_instr_map,"awo",@progbits,.text,unique,1
; CHECK-LABEL: xray_instr_map,"awo",@progbits,foo,unique,1
; CHECK: .Lxray_sleds_start0:
; CHECK-NEXT: .quad .Ltmp0
; CHECK-NEXT: .quad foo
@ -37,7 +37,7 @@ define i32 @foo() nounwind noinline uwtable "function-instrument"="xray-always"
; CHECK-NEXT: .byte 0x00
; CHECK-NEXT: .space 13
; CHECK-NEXT: .Lxray_sleds_end0:
; CHECK-LABEL: xray_fn_idx,"awo",@progbits,.text,unique,1
; CHECK-LABEL: xray_fn_idx,"awo",@progbits,foo,unique,1
; CHECK: .p2align 4
; CHECK-NEXT: .quad .Lxray_sleds_start0
; CHECK-NEXT: .quad .Lxray_sleds_end0

4
test/CodeGen/X86/xray-section-group.ll
View File

@ -5,14 +5,14 @@
define i32 @foo() nounwind noinline uwtable "function-instrument"="xray-always" {
; CHECK: .section .text.foo,"ax",@progbits
ret i32 0
; CHECK: .section xray_instr_map,"awo",@progbits,.text.foo,unique,1
; CHECK: .section xray_instr_map,"awo",@progbits,foo,unique,1
}
$bar = comdat any
define i32 @bar() nounwind noinline uwtable "function-instrument"="xray-always" comdat($bar) {
; CHECK: .section .text.bar,"axG",@progbits,bar,comdat
ret i32 1
; CHECK: .section xray_instr_map,"aGwo",@progbits,bar,comdat,.text.bar,unique,2
; CHECK: .section xray_instr_map,"aGwo",@progbits,bar,comdat,bar,unique,2
}
; CHECK-OBJ: section xray_instr_map:

84
test/DebugInfo/X86/xray-split-dwarf-interaction.ll Normal file
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@ -0,0 +1,84 @@
; RUN: %llc_dwarf -split-dwarf-file=input.dwo -O3 \
; RUN: -function-sections -data-sections \
; RUN: -relocation-model=pic -filetype=asm \
; RUN: -generate-type-units -debug-compile -o - %s | \
; RUN: FileCheck %s --check-prefix=CHECK-ASM
; RUN: %llc_dwarf -split-dwarf-file=input.dwo -O3 \
; RUN: -function-sections -data-sections \
; RUN: -relocation-model=pic -filetype=obj \
; RUN: -generate-type-units -debug-compile -o - %s | \
; RUN: llvm-readelf -sections | \
; RUN: FileCheck %s --check-prefix=CHECK-ELF
; Created from `clang++ -fxray-instrument -gsplit-dwarf -fdebug-types-section
; -ffunction-sections -fdata-sections -emit-llvm -S input.cc`:
; input.cc:
;
; class a {
; int b();
; };
; int a::b() {
; for (;;)
; ;
; }
;
; In this test we want to make sure that the xray_instr_map section for
; `a::b()` is actually associated with the function's symbol instead of the
; .debug_types.dwo section.
;
; CHECK-ASM: xray_fn_idx,"awo",@progbits,_ZN1a1bEv,unique,1
;
; CHECK-ELF-DAG: [[FSECT:[0-9]+]]] .text._ZN1a1bEv PROGBITS
; CHECK-ELF-DAG: [{{.*}}] .debug_types.dwo PROGBITS
; CHECK-ELF-DAG: [{{.*}}] xray_instr_map PROGBITS {{.*}} {{.*}} {{.*}} {{.*}} WAL [[FSECT]]
target triple = "x86_64-pc-linux"
%class.a = type { i8 }
; Function Attrs: nounwind readnone uwtable
define i32 @_ZN1a1bEv(%class.a* nocapture readnone) local_unnamed_addr #0 align 2 !dbg !8 {
tail call void @llvm.dbg.value(metadata %class.a* %0, metadata !17, metadata !DIExpression()), !dbg !19
br label %2, !dbg !20
; <label>:2: ; preds = %2, %1
br label %2, !dbg !21, !llvm.loop !25
}
; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
attributes #0 = { nounwind readnone uwtable "xray-instruction-threshold"="200" }
attributes #1 = { nounwind readnone speculatable }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5, !6}
!llvm.ident = !{!7}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version trunk (trunk r312634)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, debugInfoForProfiling: true)
!1 = !DIFile(filename: "input.cc", directory: "/usr/local/google/home/dberris/tmp")
!2 = !{}
!3 = !{i32 2, !"Debug Info Version", i32 3}
!4 = !{i32 1, !"wchar_size", i32 4}
!5 = !{i32 7, !"PIC Level", i32 2}
!6 = !{i32 7, !"PIE Level", i32 2}
!7 = !{!"clang version trunk (trunk r312634)"}
!8 = distinct !DISubprogram(name: "b", linkageName: "_ZN1a1bEv", scope: !9, file: !1, line: 4, type: !12, isLocal: false, isDefinition: true, scopeLine: 4, flags: DIFlagPrototyped, isOptimized: true, unit: !0, declaration: !11, variables: !16)
!9 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "a", file: !1, line: 1, size: 8, elements: !10, identifier: "_ZTS1a")
!10 = !{!11}
!11 = !DISubprogram(name: "b", linkageName: "_ZN1a1bEv", scope: !9, file: !1, line: 2, type: !12, isLocal: false, isDefinition: false, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true)
!12 = !DISubroutineType(types: !13)
!13 = !{!14, !15}
!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
!16 = !{!17}
!17 = !DILocalVariable(name: "this", arg: 1, scope: !8, type: !18, flags: DIFlagArtificial | DIFlagObjectPointer)
!18 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
!19 = !DILocation(line: 0, scope: !8)
!20 = !DILocation(line: 5, column: 3, scope: !8)
!21 = !DILocation(line: 5, column: 3, scope: !22)
!22 = !DILexicalBlockFile(scope: !23, file: !1, discriminator: 2)
!23 = distinct !DILexicalBlock(scope: !24, file: !1, line: 5, column: 3)
!24 = distinct !DILexicalBlock(scope: !8, file: !1, line: 5, column: 3)
!25 = distinct !{!25, !26, !27}
!26 = !DILocation(line: 5, column: 3, scope: !24)
!27 = !DILocation(line: 6, column: 5, scope: !24)