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[lld-macho] Add flag --keep-icf-stabs to LLD for MachO (#93137)

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This change adds the `--keep-icf-stabs` which, when specified, preserves
symbols that were folded by ICF in the binary's stabs entries.
This allows `dsymutil` to process debug information for the folded
symbols.
This commit is contained in:
alx32 2024-05-27 19:07:39 -07:00 committed by GitHub
parent 9ca2d60213
commit 5eea4f4425
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GPG Key ID: B5690EEEBB952194
5 changed files with 42 additions and 5 deletions
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1
lld/MachO/Config.h
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@ -193,6 +193,7 @@ struct Configuration {
UndefinedSymbolTreatment undefinedSymbolTreatment =
UndefinedSymbolTreatment::error;
ICFLevel icfLevel = ICFLevel::none;
bool keepICFStabs = false;
ObjCStubsMode objcStubsMode = ObjCStubsMode::fast;
llvm::MachO::HeaderFileType outputType;
std::vector<llvm::StringRef> systemLibraryRoots;

1
lld/MachO/Driver.cpp
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@ -1648,6 +1648,7 @@ bool link(ArrayRef<const char *> argsArr, llvm::raw_ostream &stdoutOS,
config->emitChainedFixups || args.hasArg(OPT_init_offsets);
config->emitRelativeMethodLists = shouldEmitRelativeMethodLists(args);
config->icfLevel = getICFLevel(args);
config->keepICFStabs = args.hasArg(OPT_keep_icf_stabs);
config->dedupStrings =
args.hasFlag(OPT_deduplicate_strings, OPT_no_deduplicate_strings, true);
config->deadStripDuplicates = args.hasArg(OPT_dead_strip_duplicates);

3
lld/MachO/Options.td
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@ -85,6 +85,9 @@ def icf_eq: Joined<["--"], "icf=">,
HelpText<"Set level for identical code folding (default: none)">,
MetaVarName<"[none,safe,all]">,
Group<grp_lld>;
def keep_icf_stabs: Joined<["--"], "keep-icf-stabs">,
HelpText<"Generate STABS entries for symbols folded by ICF. These entries can then be used by dsymutil to discover the address range where folded symbols are located.">,
Group<grp_lld>;
def lto_O: Joined<["--"], "lto-O">,
HelpText<"Set optimization level for LTO (default: 2)">,
MetaVarName<"<opt-level>">,

15
lld/MachO/SyntheticSections.cpp
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@ -1220,15 +1220,18 @@ void SymtabSection::emitStabs() {
continue;
// Constant-folded symbols go in the executable's symbol table, but don't
// get a stabs entry.
if (defined->wasIdenticalCodeFolded)
// get a stabs entry unless --keep-icf-stabs flag is specified
if (!config->keepICFStabs && defined->wasIdenticalCodeFolded)
continue;
ObjFile *file = defined->getObjectFile();
if (!file || !file->compileUnit)
continue;
symbolsNeedingStabs.emplace_back(defined, defined->isec()->getFile()->id);
// We use 'originalIsec' to get the file id of the symbol since 'isec()'
// might point to the merged ICF symbol's file
symbolsNeedingStabs.emplace_back(defined,
defined->originalIsec->getFile()->id);
}
}
@ -1243,7 +1246,9 @@ void SymtabSection::emitStabs() {
InputFile *lastFile = nullptr;
for (SortingPair &pair : symbolsNeedingStabs) {
Defined *defined = pair.first;
InputSection *isec = defined->isec();
// We use 'originalIsec' of the symbol since we care about the actual origin
// of the symbol, not the canonical location returned by `isec()`.
InputSection *isec = defined->originalIsec;
ObjFile *file = cast<ObjFile>(isec->getFile());
if (lastFile == nullptr || lastFile != file) {
@ -1256,7 +1261,7 @@ void SymtabSection::emitStabs() {
}
StabsEntry symStab;
symStab.sect = defined->isec()->parent->index;
symStab.sect = isec->parent->index;
symStab.strx = stringTableSection.addString(defined->getName());
symStab.value = defined->getVA();

27
lld/test/MachO/stabs-icf.s
View File

@ -4,6 +4,9 @@
# RUN: %lld -lSystem --icf=all %t.o -o %t
# RUN: dsymutil -s %t | FileCheck %s -DDIR=%t -DSRC_PATH=%t.o
# RUN: %lld -lSystem --icf=all %t.o -o %t_icf_stabs --keep-icf-stabs
# RUN: dsymutil -s %t_icf_stabs | FileCheck %s -DDIR=%t_icf_stabs -DSRC_PATH=%t.o --check-prefixes=ICF_STABS
## This should include no N_FUN entry for _baz (which is ICF'd into _bar),
## but it does include a SECT EXT entry.
## NOTE: We do not omit the N_FUN entry for _bar even though it is of size zero.
@ -27,6 +30,30 @@
# CHECK-DAG: ( {{.*}}) {{[0-9]+}} 0100 0000000000000000 'dyld_stub_binder'
# CHECK-EMPTY:
# ICF_STABS: (N_SO ) 00 0000 0000000000000000 '/tmp{{[/\\]}}test.cpp'
# ICF_STABS-NEXT: (N_OSO ) 03 0001 {{.*}} '[[SRC_PATH]]'
# ICF_STABS-NEXT: (N_FUN ) 01 0000 [[#%.16x,MAIN:]] '_main'
# ICF_STABS-NEXT: (N_FUN ) 00 0000 000000000000000b{{$}}
# ICF_STABS-NEXT: (N_FUN ) 01 0000 [[#%.16x,BAR:]] '_bar'
# ICF_STABS-NEXT: (N_FUN ) 00 0000 0000000000000000{{$}}
# ICF_STABS-NEXT: (N_FUN ) 01 0000 [[#BAR]] '_bar2'
# ICF_STABS-NEXT: (N_FUN ) 00 0000 0000000000000001{{$}}
# ICF_STABS-NEXT: (N_FUN ) 01 0000 [[#BAR]] '_baz'
# ICF_STABS-NEXT: (N_FUN ) 00 0000 0000000000000000{{$}}
# ICF_STABS-NEXT: (N_FUN ) 01 0000 [[#BAR]] '_baz2'
# ICF_STABS-NEXT: (N_FUN ) 00 0000 0000000000000001{{$}}
# ICF_STABS-NEXT: (N_SO ) 01 0000 0000000000000000{{$}}
# ICF_STABS-DAG: ( SECT EXT) 01 0000 [[#MAIN]] '_main'
# ICF_STABS-DAG: ( SECT EXT) 01 0000 [[#BAR]] '_bar'
# ICF_STABS-DAG: ( SECT EXT) 01 0000 [[#BAR]] '_bar2'
# ICF_STABS-DAG: ( SECT EXT) 01 0000 [[#BAR]] '_baz'
# ICF_STABS-DAG: ( SECT EXT) 01 0000 [[#BAR]] '_baz2'
# ICF_STABS-DAG: ( {{.*}}) {{[0-9]+}} 0010 {{[0-9a-f]+}} '__mh_execute_header'
# ICF_STABS-DAG: ( {{.*}}) {{[0-9]+}} 0100 0000000000000000 'dyld_stub_binder'
# ICF_STABS-EMPTY:
.text
.globl _bar, _bar2, _baz, _baz2, _main