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Revert "Reland D64327 [MC][ELF] Allow STT_SECTION referencing SHF_MER…
…GE on REL targets"

This reverts commit b497665.

Spent some time trying to reproduce this locally, reverting in a
desparate attempt to fix the sanitizer buildbot:
 - http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/28828

I don't know exactly why or how this patch breaks the bots, but it seems
pretty concrete that it's the culprit.
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hctim committed Aug 7, 2020
1 parent ac3e720 commit 382df1c
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Showing 7 changed files with 22 additions and 16 deletions.
9 changes: 2 additions & 7 deletions llvm/cmake/modules/AddLLVM.cmake
Expand Up @@ -222,13 +222,8 @@ function(add_link_opts target_name)
# Pass -O3 to the linker. This enabled different optimizations on different
# linkers.
if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin|SunOS|AIX" OR WIN32))
# 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()
set_property(TARGET ${target_name} APPEND_STRING PROPERTY
LINK_FLAGS " -Wl,-O3")
endif()

if(LLVM_LINKER_IS_GOLD)
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5 changes: 5 additions & 0 deletions llvm/lib/MC/ELFObjectWriter.cpp
Expand Up @@ -1393,6 +1393,11 @@ 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
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4 changes: 2 additions & 2 deletions llvm/test/MC/ELF/basic-elf-32.s
Expand Up @@ -46,9 +46,9 @@ main: # @main

// CHECK: Relocations [
// CHECK: Section {{.*}} .rel.text {
// CHECK: 0x6 R_386_32 .rodata.str1.1 0x0
// CHECK: 0x6 R_386_32 .L.str1
// CHECK: 0xB R_386_PC32 puts
// CHECK: 0x12 R_386_32 .rodata.str1.1 0x0
// CHECK: 0x12 R_386_32 .L.str2
// CHECK: 0x17 R_386_PC32 puts
// CHECK: }
// CHECK: ]
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4 changes: 2 additions & 2 deletions llvm/test/MC/ELF/compression.s
Expand Up @@ -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: .zdebug_str
// 386-SYMBOLS-GNU: Name: .Linfo_string0
// 386-SYMBOLS-GNU-NOT: }
// 386-SYMBOLS-GNU: Section: .zdebug_str

Expand Down Expand Up @@ -73,7 +73,7 @@
// ZLIB-STYLE-FLAGS32-NEXT: AddressAlignment: 4
// ZLIB-STYLE-FLAGS64-NEXT: AddressAlignment: 8

// 386-SYMBOLS-ZLIB: Name: .debug_str
// 386-SYMBOLS-ZLIB: Name: .Linfo_string0
// 386-SYMBOLS-ZLIB-NOT: }
// 386-SYMBOLS-ZLIB: Section: .debug_str

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2 changes: 1 addition & 1 deletion llvm/test/MC/ELF/relocation-386.s
Expand Up @@ -8,7 +8,7 @@
// I386: Format: elf32-i386
// CHECK: Relocations [
// CHECK-NEXT: Section {{.*}} .rel.text {
// CHECK-NEXT: 0x2 R_386_GOTOFF .rodata.str1.16 0x0
// CHECK-NEXT: 0x2 R_386_GOTOFF .Lfoo 0x0
// CHECK-NEXT: 0x{{[^ ]+}} R_386_PLT32 bar2 0x0
// CHECK-NEXT: 0x{{[^ ]+}} R_386_GOTPC _GLOBAL_OFFSET_TABLE_ 0x0
// Relocation 3 (bar3@GOTOFF) is done with symbol 7 (bss)
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10 changes: 8 additions & 2 deletions llvm/test/MC/Mips/elf-relsym.s
Expand Up @@ -4,10 +4,16 @@

// CHECK: Symbols [
// CHECK: Symbol {
// CHECK: Name: .rodata.cst8
// CHECK: Name: $.str
// CHECK: }
// CHECK: Symbol {
// CHECK: Name: .rodata.str1.1
// CHECK: Name: $.str1
// CHECK: }
// CHECK: Symbol {
// CHECK: Name: $CPI0_0
// CHECK: }
// CHECK: Symbol {
// CHECK: Name: $CPI0_1
// CHECK: }
// CHECK: ]

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4 changes: 2 additions & 2 deletions llvm/test/MC/Mips/xgot.s
Expand Up @@ -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 .rodata.str1.1 0x0
// CHECK: 0x38 R_MIPS_LO16 .rodata.str1.1 0x0
// CHECK: 0x2C R_MIPS_GOT16 $.str
// CHECK: 0x38 R_MIPS_LO16 $.str
// CHECK: ]

.text
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