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-rw-r--r--lld/ELF/Config.h5
-rw-r--r--lld/ELF/Driver.cpp70
-rw-r--r--lld/ELF/ICF.cpp5
-rw-r--r--lld/ELF/InputFiles.cpp11
-rw-r--r--lld/ELF/InputFiles.h3
-rw-r--r--lld/ELF/Options.td2
6 files changed, 85 insertions, 11 deletions
diff --git a/lld/ELF/Config.h b/lld/ELF/Config.h
index ced3cbaacb4..ec804c5296b 100644
--- a/lld/ELF/Config.h
+++ b/lld/ELF/Config.h
@@ -40,6 +40,9 @@ enum class BuildIdKind { None, Fast, Md5, Sha1, Hexstring, Uuid };
// For --discard-{all,locals,none}.
enum class DiscardPolicy { Default, All, Locals, None };
+// For --icf={none,safe,all}.
+enum class ICFLevel { None, Safe, All };
+
// For --strip-{all,debug}.
enum class StripPolicy { None, All, Debug };
@@ -138,7 +141,6 @@ struct Configuration {
bool GnuUnique;
bool HasDynamicList = false;
bool HasDynSymTab;
- bool ICF;
bool IgnoreDataAddressEquality;
bool IgnoreFunctionAddressEquality;
bool LTODebugPassManager;
@@ -187,6 +189,7 @@ struct Configuration {
bool ZRetpolineplt;
bool ZWxneeded;
DiscardPolicy Discard;
+ ICFLevel ICF;
OrphanHandlingPolicy OrphanHandling;
SortSectionPolicy SortSection;
StripPolicy Strip;
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 342e70953fb..98650a74b4e 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -51,6 +51,7 @@
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compression.h"
+#include "llvm/Support/LEB128.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/TarWriter.h"
#include "llvm/Support/TargetSelect.h"
@@ -296,7 +297,7 @@ static void checkOptions(opt::InputArgList &Args) {
error("-r and --gc-sections may not be used together");
if (Config->GdbIndex)
error("-r and --gdb-index may not be used together");
- if (Config->ICF)
+ if (Config->ICF != ICFLevel::None)
error("-r and --icf may not be used together");
if (Config->Pie)
error("-r and -pie may not be used together");
@@ -519,6 +520,15 @@ static StringRef getDynamicLinker(opt::InputArgList &Args) {
return Arg->getValue();
}
+static ICFLevel getICF(opt::InputArgList &Args) {
+ auto *Arg = Args.getLastArg(OPT_icf_none, OPT_icf_safe, OPT_icf_all);
+ if (!Arg || Arg->getOption().getID() == OPT_icf_none)
+ return ICFLevel::None;
+ if (Arg->getOption().getID() == OPT_icf_safe)
+ return ICFLevel::Safe;
+ return ICFLevel::All;
+}
+
static StripPolicy getStrip(opt::InputArgList &Args) {
if (Args.hasArg(OPT_relocatable))
return StripPolicy::None;
@@ -745,7 +755,7 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
Config->GcSections = Args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, false);
Config->GnuUnique = Args.hasFlag(OPT_gnu_unique, OPT_no_gnu_unique, true);
Config->GdbIndex = Args.hasFlag(OPT_gdb_index, OPT_no_gdb_index, false);
- Config->ICF = Args.hasFlag(OPT_icf_all, OPT_icf_none, false);
+ Config->ICF = getICF(Args);
Config->IgnoreDataAddressEquality =
Args.hasArg(OPT_ignore_data_address_equality);
Config->IgnoreFunctionAddressEquality =
@@ -1225,16 +1235,60 @@ template <class ELFT> static void demoteSymbols() {
}
}
+static bool keepUnique(Symbol *S) {
+ if (auto *D = dyn_cast_or_null<Defined>(S)) {
+ if (D->Section) {
+ D->Section->KeepUnique = true;
+ return true;
+ }
+ }
+ return false;
+}
+
// Record sections that define symbols mentioned in --keep-unique <symbol>
-// these sections are inelligible for ICF.
+// and symbols referred to by address-significance tables. These sections are
+// ineligible for ICF.
+template <class ELFT>
static void findKeepUniqueSections(opt::InputArgList &Args) {
for (auto *Arg : Args.filtered(OPT_keep_unique)) {
StringRef Name = Arg->getValue();
- if (auto *Sym = dyn_cast_or_null<Defined>(Symtab->find(Name)))
- Sym->Section->KeepUnique = true;
- else
+ if (!keepUnique(Symtab->find(Name)))
warn("could not find symbol " + Name + " to keep unique");
}
+
+ if (Config->ICF == ICFLevel::Safe) {
+ // Symbols in the dynsym could be address-significant in other executables
+ // or DSOs, so we conservatively mark them as address-significant.
+ for (Symbol *S : Symtab->getSymbols())
+ if (S->includeInDynsym())
+ keepUnique(S);
+
+ // Visit the address-significance table in each object file and mark each
+ // referenced symbol as address-significant.
+ for (InputFile *F : ObjectFiles) {
+ auto *Obj = cast<ObjFile<ELFT>>(F);
+ ArrayRef<Symbol *> Syms = Obj->getSymbols();
+ if (Obj->AddrsigSec) {
+ ArrayRef<uint8_t> Contents =
+ check(Obj->getObj().getSectionContents(Obj->AddrsigSec));
+ const uint8_t *Cur = Contents.begin();
+ while (Cur != Contents.end()) {
+ unsigned Size;
+ const char *Err;
+ uint64_t SymIndex = decodeULEB128(Cur, &Size, Contents.end(), &Err);
+ if (Err)
+ fatal(toString(F) + ": could not decode addrsig section: " + Err);
+ keepUnique(Syms[SymIndex]);
+ Cur += Size;
+ }
+ } else {
+ // If an object file does not have an address-significance table,
+ // conservatively mark all of its symbols as address-significant.
+ for (Symbol *S : Syms)
+ keepUnique(S);
+ }
+ }
+ }
}
// Do actual linking. Note that when this function is called,
@@ -1409,8 +1463,8 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
markLive<ELFT>();
demoteSymbols<ELFT>();
mergeSections();
- if (Config->ICF) {
- findKeepUniqueSections(Args);
+ if (Config->ICF != ICFLevel::None) {
+ findKeepUniqueSections<ELFT>(Args);
doIcf<ELFT>();
}
diff --git a/lld/ELF/ICF.cpp b/lld/ELF/ICF.cpp
index 9ede87733d2..f13a5049e01 100644
--- a/lld/ELF/ICF.cpp
+++ b/lld/ELF/ICF.cpp
@@ -173,8 +173,9 @@ static bool isEligible(InputSection *S) {
return false;
// Don't merge read only data sections unless
- // --ignore-data-address-equality was passed.
- if (!(S->Flags & SHF_EXECINSTR) && !Config->IgnoreDataAddressEquality)
+ // --ignore-data-address-equality or --icf=safe was passed.
+ if (!(S->Flags & SHF_EXECINSTR) &&
+ !(Config->IgnoreDataAddressEquality || Config->ICF == ICFLevel::Safe))
return false;
// Don't merge synthetic sections as their Data member is not valid and empty.
diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index e68c3bdf8d4..6da722f6f30 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -420,6 +420,17 @@ void ObjFile<ELFT>::initializeSections(
// if -r is given, we'll let the final link discard such sections.
// This is compatible with GNU.
if ((Sec.sh_flags & SHF_EXCLUDE) && !Config->Relocatable) {
+ if (Sec.sh_type == SHT_LLVM_ADDRSIG) {
+ // We ignore the address-significance table if we know that the object
+ // file was created by objcopy or ld -r. This is because these tools
+ // will reorder the symbols in the symbol table, invalidating the data
+ // in the address-significance table, which refers to symbols by index.
+ if (Sec.sh_link != 0)
+ this->AddrsigSec = &Sec;
+ else if (Config->ICF == ICFLevel::Safe)
+ warn(toString(this) + ": --icf=safe is incompatible with object "
+ "files created using objcopy or ld -r");
+ }
this->Sections[I] = &InputSection::Discarded;
continue;
}
diff --git a/lld/ELF/InputFiles.h b/lld/ELF/InputFiles.h
index f6c9d94e881..0db3203b0ba 100644
--- a/lld/ELF/InputFiles.h
+++ b/lld/ELF/InputFiles.h
@@ -215,6 +215,9 @@ public:
// but had one or more functions with the no_split_stack attribute.
bool SomeNoSplitStack = false;
+ // Pointer to this input file's .llvm_addrsig section, if it has one.
+ const Elf_Shdr *AddrsigSec = nullptr;
+
private:
void
initializeSections(llvm::DenseSet<llvm::CachedHashStringRef> &ComdatGroups);
diff --git a/lld/ELF/Options.td b/lld/ELF/Options.td
index acccb795486..73457db8332 100644
--- a/lld/ELF/Options.td
+++ b/lld/ELF/Options.td
@@ -170,6 +170,8 @@ def help: F<"help">, HelpText<"Print option help">;
def icf_all: F<"icf=all">, HelpText<"Enable identical code folding">;
+def icf_safe: F<"icf=safe">, HelpText<"Enable safe identical code folding">;
+
def icf_none: F<"icf=none">, HelpText<"Disable identical code folding (default)">;
def ignore_function_address_equality: F<"ignore-function-address-equality">,
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