[llvm] b497665 - Reland D64327 [MC][ELF] Allow STT_SECTION referencing SHF_MERGE on REL targets
Vitaly Buka via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 5 04:05:48 PDT 2020
Probably also these as well
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-android/builds/34196
On Wed, 5 Aug 2020 at 04:04, Vitaly Buka <vitalybuka at google.com> wrote:
> It fails CFI tests
> http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/28828
>
>
> On Sun, 2 Aug 2020 at 18:06, Fangrui Song via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>>
>> Author: Fangrui Song
>> Date: 2020-08-02T18:05:17-07:00
>> New Revision: b497665d98ad5026b1d3d67d5793a28fefe27bea
>>
>> URL:
>> https://github.com/llvm/llvm-project/commit/b497665d98ad5026b1d3d67d5793a28fefe27bea
>> DIFF:
>> https://github.com/llvm/llvm-project/commit/b497665d98ad5026b1d3d67d5793a28fefe27bea.diff
>>
>> LOG: Reland D64327 [MC][ELF] Allow STT_SECTION referencing SHF_MERGE on
>> REL targets
>>
>> This drops a GNU gold workaround and reverts the revert commit rL366708.
>>
>> Before binutils 2.34, gold -O2 and above did not correctly handle
>> R_386_GOTOFF to
>> SHF_MERGE|SHF_STRINGS sections:
>> https://sourceware.org/bugzilla/show_bug.cgi?id=16794
>>
>> >From the original review:
>>
>> ... it reduced the size of a big ARM-32 debug image by 33%. It
>> contained ~68M
>> of relocations symbols out of total ~71M symbols (96% of symbols table
>> was
>> generated for relocations with symbol).
>>
>> -Wl,-O2 (and -Wl,-O3) is so rare that we should just lower the
>> optimization level for LLVM_LINKER_IS_GOLD rather than pessimizing all
>> users.
>>
>> Added:
>>
>>
>> Modified:
>> llvm/cmake/modules/AddLLVM.cmake
>> llvm/lib/MC/ELFObjectWriter.cpp
>> llvm/test/MC/ELF/basic-elf-32.s
>> llvm/test/MC/ELF/compression.s
>> llvm/test/MC/ELF/relocation-386.s
>> llvm/test/MC/Mips/elf-relsym.s
>> llvm/test/MC/Mips/xgot.s
>>
>> Removed:
>>
>>
>>
>>
>> ################################################################################
>> diff --git a/llvm/cmake/modules/AddLLVM.cmake
>> b/llvm/cmake/modules/AddLLVM.cmake
>> index 333167bfb6b0..a25f3e87af61 100644
>> --- a/llvm/cmake/modules/AddLLVM.cmake
>> +++ b/llvm/cmake/modules/AddLLVM.cmake
>> @@ -222,8 +222,13 @@ function(add_link_opts target_name)
>> # Pass -O3 to the linker. This enabled
>> diff erent optimizations on
>> diff erent
>> # linkers.
>> if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin|SunOS|AIX" OR WIN32))
>> - set_property(TARGET ${target_name} APPEND_STRING PROPERTY
>> - LINK_FLAGS " -Wl,-O3")
>> + # Before binutils 2.34, gold -O2 and above did not correctly
>> handle R_386_GOTOFF to
>> + # SHF_MERGE|SHF_STRINGS sections:
>> https://sourceware.org/bugzilla/show_bug.cgi?id=16794
>> + if(LLVM_LINKER_IS_GOLD)
>> + set_property(TARGET ${target_name} APPEND_STRING PROPERTY
>> LINK_FLAGS " -Wl,-O1")
>> + else()
>> + set_property(TARGET ${target_name} APPEND_STRING PROPERTY
>> LINK_FLAGS " -Wl,-O3")
>> + endif()
>> endif()
>>
>> if(LLVM_LINKER_IS_GOLD)
>>
>> diff --git a/llvm/lib/MC/ELFObjectWriter.cpp
>> b/llvm/lib/MC/ELFObjectWriter.cpp
>> index 1ca9d0fe1e18..5a5692c0cb63 100644
>> --- a/llvm/lib/MC/ELFObjectWriter.cpp
>> +++ b/llvm/lib/MC/ELFObjectWriter.cpp
>> @@ -1389,11 +1389,6 @@ bool
>> ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
>> if (Flags & ELF::SHF_MERGE) {
>> if (C != 0)
>> return true;
>> -
>> - // It looks like gold has a bug (http://sourceware.org/PR16794)
>> and can
>> - // only handle section relocations to mergeable sections if using
>> RELA.
>> - if (!hasRelocationAddend())
>> - return true;
>> }
>>
>> // Most TLS relocations use a got, so they need the symbol. Even
>> those that
>>
>> diff --git a/llvm/test/MC/ELF/basic-elf-32.s
>> b/llvm/test/MC/ELF/basic-elf-32.s
>> index effc363d1c6c..1a923106036a 100644
>> --- a/llvm/test/MC/ELF/basic-elf-32.s
>> +++ b/llvm/test/MC/ELF/basic-elf-32.s
>> @@ -46,9 +46,9 @@ main: # @main
>>
>> // CHECK: Relocations [
>> // CHECK: Section {{.*}} .rel.text {
>> -// CHECK: 0x6 R_386_32 .L.str1
>> +// CHECK: 0x6 R_386_32 .rodata.str1.1 0x0
>> // CHECK: 0xB R_386_PC32 puts
>> -// CHECK: 0x12 R_386_32 .L.str2
>> +// CHECK: 0x12 R_386_32 .rodata.str1.1 0x0
>> // CHECK: 0x17 R_386_PC32 puts
>> // CHECK: }
>> // CHECK: ]
>>
>> diff --git a/llvm/test/MC/ELF/compression.s
>> b/llvm/test/MC/ELF/compression.s
>> index 93a77b3fcbdb..9bc5c0ecc699 100644
>> --- a/llvm/test/MC/ELF/compression.s
>> +++ b/llvm/test/MC/ELF/compression.s
>> @@ -38,7 +38,7 @@
>>
>> // In x86 32 bit named symbols are used for temporary symbols in merge
>> // sections, so make sure we handle symbols inside compressed sections
>> -// 386-SYMBOLS-GNU: Name: .Linfo_string0
>> +// 386-SYMBOLS-GNU: Name: .zdebug_str
>> // 386-SYMBOLS-GNU-NOT: }
>> // 386-SYMBOLS-GNU: Section: .zdebug_str
>>
>> @@ -73,7 +73,7 @@
>> // ZLIB-STYLE-FLAGS32-NEXT: AddressAlignment: 4
>> // ZLIB-STYLE-FLAGS64-NEXT: AddressAlignment: 8
>>
>> -// 386-SYMBOLS-ZLIB: Name: .Linfo_string0
>> +// 386-SYMBOLS-ZLIB: Name: .debug_str
>> // 386-SYMBOLS-ZLIB-NOT: }
>> // 386-SYMBOLS-ZLIB: Section: .debug_str
>>
>>
>> diff --git a/llvm/test/MC/ELF/relocation-386.s
>> b/llvm/test/MC/ELF/relocation-386.s
>> index 4273750a4192..b9bf9b6a00c1 100644
>> --- a/llvm/test/MC/ELF/relocation-386.s
>> +++ b/llvm/test/MC/ELF/relocation-386.s
>> @@ -8,7 +8,7 @@
>> // I386: Format: elf32-i386
>> // CHECK: Relocations [
>> // CHECK-NEXT: Section {{.*}} .rel.text {
>> -// CHECK-NEXT: 0x2 R_386_GOTOFF .Lfoo 0x0
>> +// CHECK-NEXT: 0x2 R_386_GOTOFF .rodata.str1.16 0x0
>> // CHECK-NEXT: 0x{{[^ ]+}} R_386_PLT32 bar2 0x0
>> // CHECK-NEXT: 0x{{[^ ]+}} R_386_GOTPC _GLOBAL_OFFSET_TABLE_
>> 0x0
>> // Relocation 3 (bar3 at GOTOFF) is done with symbol 7 (bss)
>>
>> diff --git a/llvm/test/MC/Mips/elf-relsym.s
>> b/llvm/test/MC/Mips/elf-relsym.s
>> index b8c2f89e82e6..d19b4e3c4820 100644
>> --- a/llvm/test/MC/Mips/elf-relsym.s
>> +++ b/llvm/test/MC/Mips/elf-relsym.s
>> @@ -4,16 +4,10 @@
>>
>> // CHECK: Symbols [
>> // CHECK: Symbol {
>> -// CHECK: Name: $.str
>> +// CHECK: Name: .rodata.cst8
>> // CHECK: }
>> // CHECK: Symbol {
>> -// CHECK: Name: $.str1
>> -// CHECK: }
>> -// CHECK: Symbol {
>> -// CHECK: Name: $CPI0_0
>> -// CHECK: }
>> -// CHECK: Symbol {
>> -// CHECK: Name: $CPI0_1
>> +// CHECK: Name: .rodata.str1.1
>> // CHECK: }
>> // CHECK: ]
>>
>>
>> diff --git a/llvm/test/MC/Mips/xgot.s b/llvm/test/MC/Mips/xgot.s
>> index 100d25e67223..76490f0dec93 100644
>> --- a/llvm/test/MC/Mips/xgot.s
>> +++ b/llvm/test/MC/Mips/xgot.s
>> @@ -10,8 +10,8 @@
>> // CHECK: 0x1C R_MIPS_GOT_LO16 ext_1
>> // CHECK: 0x24 R_MIPS_CALL_HI16 printf
>> // CHECK: 0x30 R_MIPS_CALL_LO16 printf
>> -// CHECK: 0x2C R_MIPS_GOT16 $.str
>> -// CHECK: 0x38 R_MIPS_LO16 $.str
>> +// CHECK: 0x2C R_MIPS_GOT16 .rodata.str1.1 0x0
>> +// CHECK: 0x38 R_MIPS_LO16 .rodata.str1.1 0x0
>> // CHECK: ]
>>
>> .text
>>
>>
>>
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