[llvm] b497665 - Reland D64327 [MC][ELF] Allow STT_SECTION referencing SHF_MERGE on REL targets
Fangrui Song via llvm-commits
llvm-commits at lists.llvm.org
Sun Aug 2 18:06:33 PDT 2020
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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