[lld] r337429 - ELF: Implement --icf=safe using address-significance tables.
Peter Collingbourne via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 26 15:17:23 PDT 2018
Thanks for letting me know. I've sent https://reviews.llvm.org/D49877 with
a fix.
I wonder whether that bot should be renamed. Despite having "x86_64" in its
name, it actually builds 32-bit binaries. The fact that it was doing so was
the cause of the test failure.
Peter
On Thu, Jul 26, 2018 at 9:58 AM Galina Kistanova <gkistanova at gmail.com>
wrote:
> Hello Peter,
>
> This commit broke tests on one of our builders:
>
> http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-windows10pro-fast/builds/18560
>
> . . .
> Failing Tests (1):
> lld :: ELF/icf-safe.s
>
> Please have a look?
> The builder was already red and did not sent any notifications on this.
>
> Thanks
>
> Galina
>
> On Wed, Jul 18, 2018 at 3:49 PM, Peter Collingbourne via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: pcc
>> Date: Wed Jul 18 15:49:31 2018
>> New Revision: 337429
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=337429&view=rev
>> Log:
>> ELF: Implement --icf=safe using address-significance tables.
>>
>> Differential Revision: https://reviews.llvm.org/D48146
>>
>> Added:
>> lld/trunk/test/ELF/Inputs/icf-safe.s
>> lld/trunk/test/ELF/icf-safe.s
>> Modified:
>> lld/trunk/ELF/Config.h
>> lld/trunk/ELF/Driver.cpp
>> lld/trunk/ELF/ICF.cpp
>> lld/trunk/ELF/InputFiles.cpp
>> lld/trunk/ELF/InputFiles.h
>> lld/trunk/ELF/Options.td
>> lld/trunk/docs/ld.lld.1
>>
>> Modified: lld/trunk/ELF/Config.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Config.h?rev=337429&r1=337428&r2=337429&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/Config.h (original)
>> +++ lld/trunk/ELF/Config.h Wed Jul 18 15:49:31 2018
>> @@ -40,6 +40,9 @@ enum class BuildIdKind { None, Fast, Md5
>> // 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;
>>
>> Modified: lld/trunk/ELF/Driver.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Driver.cpp?rev=337429&r1=337428&r2=337429&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/Driver.cpp (original)
>> +++ lld/trunk/ELF/Driver.cpp Wed Jul 18 15:49:31 2018
>> @@ -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::InputArgLi
>> 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::I
>> 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::Inpu
>> 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 demote
>> }
>> }
>>
>> +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:
>> markLive<ELFT>();
>> demoteSymbols<ELFT>();
>> mergeSections();
>> - if (Config->ICF) {
>> - findKeepUniqueSections(Args);
>> + if (Config->ICF != ICFLevel::None) {
>> + findKeepUniqueSections<ELFT>(Args);
>> doIcf<ELFT>();
>> }
>>
>>
>> Modified: lld/trunk/ELF/ICF.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/ICF.cpp?rev=337429&r1=337428&r2=337429&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/ICF.cpp (original)
>> +++ lld/trunk/ELF/ICF.cpp Wed Jul 18 15:49:31 2018
>> @@ -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.
>>
>> Modified: lld/trunk/ELF/InputFiles.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=337429&r1=337428&r2=337429&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/InputFiles.cpp (original)
>> +++ lld/trunk/ELF/InputFiles.cpp Wed Jul 18 15:49:31 2018
>> @@ -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;
>> }
>>
>> Modified: lld/trunk/ELF/InputFiles.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.h?rev=337429&r1=337428&r2=337429&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/InputFiles.h (original)
>> +++ lld/trunk/ELF/InputFiles.h Wed Jul 18 15:49:31 2018
>> @@ -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);
>>
>> Modified: lld/trunk/ELF/Options.td
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Options.td?rev=337429&r1=337428&r2=337429&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/Options.td (original)
>> +++ lld/trunk/ELF/Options.td Wed Jul 18 15:49:31 2018
>> @@ -170,6 +170,8 @@ def help: F<"help">, HelpText<"Print opt
>>
>> 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">,
>>
>> Modified: lld/trunk/docs/ld.lld.1
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/docs/ld.lld.1?rev=337429&r1=337428&r2=337429&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/docs/ld.lld.1 (original)
>> +++ lld/trunk/docs/ld.lld.1 Wed Jul 18 15:49:31 2018
>> @@ -187,6 +187,8 @@ is the default.
>> Print a help message.
>> .It Fl -icf Ns = Ns Cm all
>> Enable identical code folding.
>> +.It Fl -icf Ns = Ns Cm safe
>> +Enable safe identical code folding.
>> .It Fl -icf Ns = Ns Cm none
>> Disable identical code folding.
>> .It Fl -image-base Ns = Ns Ar value
>>
>> Added: lld/trunk/test/ELF/Inputs/icf-safe.s
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/Inputs/icf-safe.s?rev=337429&view=auto
>>
>> ==============================================================================
>> --- lld/trunk/test/ELF/Inputs/icf-safe.s (added)
>> +++ lld/trunk/test/ELF/Inputs/icf-safe.s Wed Jul 18 15:49:31 2018
>> @@ -0,0 +1,9 @@
>> +.section .text.non_addrsig1,"ax", at progbits
>> +.globl non_addrsig1
>> +non_addrsig1:
>> +ret
>> +
>> +.section .text.non_addrsig2,"ax", at progbits
>> +.globl non_addrsig2
>> +non_addrsig2:
>> +ret
>>
>> Added: lld/trunk/test/ELF/icf-safe.s
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/icf-safe.s?rev=337429&view=auto
>>
>> ==============================================================================
>> --- lld/trunk/test/ELF/icf-safe.s (added)
>> +++ lld/trunk/test/ELF/icf-safe.s Wed Jul 18 15:49:31 2018
>> @@ -0,0 +1,137 @@
>> +# REQUIRES: x86
>> +
>> +# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
>> +# RUN: llvm-objcopy %t1.o %t1copy.o
>> +# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux
>> %S/Inputs/icf-safe.s -o %t2.o
>> +# RUN: ld.lld %t1.o %t2.o -o %t2 --icf=safe --print-icf-sections |
>> FileCheck %s
>> +# RUN: ld.lld %t1.o %t2.o -o %t3 --icf=safe --print-icf-sections -shared
>> | FileCheck --check-prefix=EXPORT %s
>> +# RUN: ld.lld %t1.o %t2.o -o %t3 --icf=safe --print-icf-sections
>> --export-dynamic | FileCheck --check-prefix=EXPORT %s
>> +# RUN: ld.lld %t1copy.o -o %t4 --icf=safe 2>&1 | FileCheck
>> --check-prefix=OBJCOPY %s
>> +
>> +# CHECK-NOT: selected section {{.*}}:(.rodata.l1)
>> +# CHECK: selected section {{.*}}:(.rodata.l3)
>> +# CHECK: removing identical section {{.*}}:(.rodata.l4)
>> +
>> +# CHECK-NOT: selected section {{.*}}:(.text.f1)
>> +# CHECK: selected section {{.*}}:(.text.f3)
>> +# CHECK: removing identical section {{.*}}:(.text.f4)
>> +
>> +# CHECK-NOT: selected section {{.*}}:(.rodata.h1)
>> +# CHECK: selected section {{.*}}:(.rodata.h3)
>> +# CHECK: removing identical section {{.*}}:(.rodata.h4)
>> +
>> +# CHECK-NOT: selected section {{.*}}:(.rodata.g1)
>> +# CHECK: selected section {{.*}}:(.rodata.g3)
>> +# CHECK: removing identical section {{.*}}:(.rodata.g4)
>> +
>> +# CHECK-NOT: selected section {{.*}}:(.text.non_addrsig{{.}})
>> +
>> +# llvm-mc normally emits an empty .text section into every object file.
>> Since
>> +# nothing actually refers to it via a relocation, it doesn't have any
>> associated
>> +# symbols (thus nor can anything refer to it via a relocation, making it
>> safe to
>> +# merge with the empty section in the other input file). Here we check
>> that the
>> +# only two sections merged are the two empty sections and the sections
>> with only
>> +# STB_LOCAL or STV_HIDDEN symbols. The dynsym entries should have
>> prevented
>> +# anything else from being merged.
>> +# EXPORT-NOT: selected section
>> +# EXPORT: selected section {{.*}}:(.rodata.l3)
>> +# EXPORT: removing identical section {{.*}}:(.rodata.l4)
>> +# EXPORT-NOT: selected section
>> +# EXPORT: selected section {{.*}}:(.rodata.h3)
>> +# EXPORT: removing identical section {{.*}}:(.rodata.h4)
>> +# EXPORT-NOT: selected section
>> +# EXPORT: selected section {{.*}}:(.text)
>> +# EXPORT: removing identical section {{.*}}:(.text)
>> +# EXPORT-NOT: selected section
>> +
>> +# OBJCOPY: --icf=safe is incompatible with object files created using
>> objcopy or ld -r
>> +
>> +.section .text.f1,"ax", at progbits
>> +.globl f1
>> +f1:
>> +ret
>> +
>> +.section .text.f2,"ax", at progbits
>> +.globl f2
>> +f2:
>> +ret
>> +
>> +.section .text.f3,"ax", at progbits
>> +.globl f3
>> +f3:
>> +ud2
>> +
>> +.section .text.f4,"ax", at progbits
>> +.globl f4
>> +f4:
>> +ud2
>> +
>> +.section .rodata.g1,"a", at progbits
>> +.globl g1
>> +g1:
>> +.byte 1
>> +
>> +.section .rodata.g2,"a", at progbits
>> +.globl g2
>> +g2:
>> +.byte 1
>> +
>> +.section .rodata.g3,"a", at progbits
>> +.globl g3
>> +g3:
>> +.byte 2
>> +
>> +.section .rodata.g4,"a", at progbits
>> +.globl g4
>> +g4:
>> +.byte 2
>> +
>> +.section .rodata.l1,"a", at progbits
>> +l1:
>> +.byte 3
>> +
>> +.section .rodata.l2,"a", at progbits
>> +l2:
>> +.byte 3
>> +
>> +.section .rodata.l3,"a", at progbits
>> +l3:
>> +.byte 4
>> +
>> +.section .rodata.l4,"a", at progbits
>> +l4:
>> +.byte 4
>> +
>> +.section .rodata.h1,"a", at progbits
>> +.globl h1
>> +.hidden h1
>> +h1:
>> +.byte 5
>> +
>> +.section .rodata.h2,"a", at progbits
>> +.globl h2
>> +.hidden h2
>> +h2:
>> +.byte 5
>> +
>> +.section .rodata.h3,"a", at progbits
>> +.globl h3
>> +.hidden h3
>> +h3:
>> +.byte 6
>> +
>> +.section .rodata.h4,"a", at progbits
>> +.globl h4
>> +.hidden h4
>> +h4:
>> +.byte 6
>> +
>> +.addrsig
>> +.addrsig_sym f1
>> +.addrsig_sym f2
>> +.addrsig_sym g1
>> +.addrsig_sym g2
>> +.addrsig_sym l1
>> +.addrsig_sym l2
>> +.addrsig_sym h1
>> +.addrsig_sym h2
>>
>>
>> _______________________________________________
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>> llvm-commits at lists.llvm.org
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>>
>
>
--
--
Peter
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