diff --git a/llvm/docs/BitCodeFormat.rst b/llvm/docs/BitCodeFormat.rst --- a/llvm/docs/BitCodeFormat.rst +++ b/llvm/docs/BitCodeFormat.rst @@ -470,13 +470,18 @@ Bitcode files for LLVM IR may also be wrapped in a native object file (i.e. ELF, COFF, Mach-O). The bitcode must be stored in a section of the object -file named ``__LLVM,__bitcode`` for MachO and ``.llvmbc`` for the other object -formats. This wrapper format is useful for accommodating LTO in compilation -pipelines where intermediate objects must be native object files which contain -metadata in other sections. +file named ``__LLVM,__bitcode`` for MachO or ``.llvmbc`` for the other object +formats. ELF objects additionally support a ``.llvm.lto`` section for +:doc:`FatLTO`, which contains bitcode suitable for LTO compilation (i.e. bitcode +that has gone through a pre-link LTO pipeline). The ``.llvmbc`` section +predates FatLTO support in LLVM, and may not always contain bitcode that is +suitable for LTO (i.e. from ``-fembed-bitcode``). The wrapper format is useful +for accommodating LTO in compilation pipelines where intermediate objects must +be native object files which contain metadata in other sections. Not all tools support this format. For example, lld and the gold plugin will -ignore these sections when linking object files. +ignore the ``.llvmbc`` section when linking object files, but can use +``.llvm.lto`` sections when passed the correct command line options. .. _encoding of LLVM IR: diff --git a/llvm/lib/Object/ObjectFile.cpp b/llvm/lib/Object/ObjectFile.cpp --- a/llvm/lib/Object/ObjectFile.cpp +++ b/llvm/lib/Object/ObjectFile.cpp @@ -79,7 +79,7 @@ bool ObjectFile::isSectionBitcode(DataRefImpl Sec) const { Expected NameOrErr = getSectionName(Sec); if (NameOrErr) - return *NameOrErr == ".llvmbc" || *NameOrErr == ".llvm.lto"; + return *NameOrErr == ".llvm.lto"; consumeError(NameOrErr.takeError()); return false; } diff --git a/llvm/test/LTO/X86/Inputs/bcsection.macho.s b/llvm/test/LTO/X86/Inputs/bcsection.macho.s --- a/llvm/test/LTO/X86/Inputs/bcsection.macho.s +++ b/llvm/test/LTO/X86/Inputs/bcsection.macho.s @@ -2,4 +2,4 @@ .asciz "Wrong Section" .section __LLVM,__bitcode -.incbin "bcsection.bc" +.incbin "llvm.lto.section.bc" diff --git a/llvm/test/LTO/X86/Inputs/llvm.lto.section.s b/llvm/test/LTO/X86/Inputs/llvm.lto.section.s new file mode 100644 --- /dev/null +++ b/llvm/test/LTO/X86/Inputs/llvm.lto.section.s @@ -0,0 +1,2 @@ +.section .llvm.lto +.incbin "llvm.lto.section.bc" diff --git a/llvm/test/LTO/X86/bcsection.ll b/llvm/test/LTO/X86/bcsection.ll --- a/llvm/test/LTO/X86/bcsection.ll +++ b/llvm/test/LTO/X86/bcsection.ll @@ -2,23 +2,17 @@ ; RUN: llvm-as -o %t/bcsection.bc %s ; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-pc-win32 -o %t/bcsection.coff.bco %p/Inputs/bcsection.s -; RUN: llvm-nm %t/bcsection.coff.bco | FileCheck %s -; RUN: llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/bcsection.coff.o %t/bcsection.coff.bco -; RUN: llvm-nm %t/bcsection.coff.o | FileCheck %s +; RUN: llvm-nm %t/bcsection.coff.bco | FileCheck %s --allow-empty +; RUN: not llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/bcsection.coff.o %t/bcsection.coff.bco ; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-unknown-linux-gnu -o %t/bcsection.elf.bco %p/Inputs/bcsection.s -; RUN: llvm-nm %t/bcsection.elf.bco | FileCheck %s -; RUN: llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/bcsection.elf.o %t/bcsection.elf.bco -; RUN: llvm-nm %t/bcsection.elf.o | FileCheck %s - -; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-apple-darwin11 -o %t/bcsection.macho.bco %p/Inputs/bcsection.macho.s -; RUN: llvm-nm %t/bcsection.macho.bco | FileCheck %s -; RUN: llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/bcsection.macho.o %t/bcsection.macho.bco -; RUN: llvm-nm %t/bcsection.macho.o | FileCheck %s +; RUN: llvm-nm %t/bcsection.elf.bco | FileCheck %s --allow-empty +; RUN: not llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/bcsection.elf.o %t/bcsection.elf.bco target triple = "x86_64-unknown-linux-gnu" -; CHECK: main +;; The .llvmbc section is not intended for use with LTO, so there should be nothing here +; CHECK-NOT: main define i32 @main() { ret i32 0 } diff --git a/llvm/test/LTO/X86/bcsection.ll b/llvm/test/LTO/X86/llvm.lto.section.ll copy from llvm/test/LTO/X86/bcsection.ll copy to llvm/test/LTO/X86/llvm.lto.section.ll --- a/llvm/test/LTO/X86/bcsection.ll +++ b/llvm/test/LTO/X86/llvm.lto.section.ll @@ -1,15 +1,16 @@ ; RUN: rm -rf %t && mkdir -p %t -; RUN: llvm-as -o %t/bcsection.bc %s +; RUN: llvm-as -o %t/llvm.lto.section.bc %s -; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-pc-win32 -o %t/bcsection.coff.bco %p/Inputs/bcsection.s -; RUN: llvm-nm %t/bcsection.coff.bco | FileCheck %s -; RUN: llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/bcsection.coff.o %t/bcsection.coff.bco -; RUN: llvm-nm %t/bcsection.coff.o | FileCheck %s +; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-pc-win32 -o %t/llvm.lto.section.coff.bco %p/Inputs/llvm.lto.section.s +; RUN: llvm-nm %t/llvm.lto.section.coff.bco | FileCheck %s +; RUN: llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/llvm.lto.section.coff.o %t/llvm.lto.section.coff.bco +; RUN: llvm-nm %t/llvm.lto.section.coff.o | FileCheck %s + +; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-unknown-linux-gnu -o %t/llvm.lto.section.elf.bco %p/Inputs/llvm.lto.section.s +; RUN: llvm-nm %t/llvm.lto.section.elf.bco | FileCheck %s +; RUN: llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/llvm.lto.section.elf.o %t/llvm.lto.section.elf.bco +; RUN: llvm-nm %t/llvm.lto.section.elf.o | FileCheck %s -; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-unknown-linux-gnu -o %t/bcsection.elf.bco %p/Inputs/bcsection.s -; RUN: llvm-nm %t/bcsection.elf.bco | FileCheck %s -; RUN: llvm-lto -exported-symbol=main -exported-symbol=_main -o %t/bcsection.elf.o %t/bcsection.elf.bco -; RUN: llvm-nm %t/bcsection.elf.o | FileCheck %s ; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-apple-darwin11 -o %t/bcsection.macho.bco %p/Inputs/bcsection.macho.s ; RUN: llvm-nm %t/bcsection.macho.bco | FileCheck %s diff --git a/llvm/test/tools/gold/X86/fatlto/fatlto.invalid.s b/llvm/test/tools/gold/X86/fatlto/fatlto.invalid.s new file mode 100644 --- /dev/null +++ b/llvm/test/tools/gold/X86/fatlto/fatlto.invalid.s @@ -0,0 +1,11 @@ +# REQUIRES: x86_64-linux + +# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t +# RUN: not %gold -plugin %llvmshlibdir/LLVMgold%shlibext %t -o /dev/null 2>&1 | FileCheck %s + +# CHECK: error:{{.*}} Invalid bitcode signature + +.section .llvm.lto,"e",@progbits +.Lllvm.embedded.object: + .asciz "BC\300\3365\000" + .size .Lllvm.embedded.object, 12 diff --git a/llvm/test/tools/gold/X86/fatlto/fatlto.test b/llvm/test/tools/gold/X86/fatlto/fatlto.test new file mode 100644 --- /dev/null +++ b/llvm/test/tools/gold/X86/fatlto/fatlto.test @@ -0,0 +1,109 @@ +;; Basic FatLTO tests. +; REQUIRES: x86_64-linux + +; RUN: rm -rf %t && split-file %s %t + +;; Ensure that input files contain .llvm.lto section +; RUN: llc %t/a-LTO.ll --filetype=obj -o %t/a-fatLTO.o +; RUN: opt --module-summary %t/a-LTO.ll -o %t/a-fatLTO.bc +; RUN: llvm-objcopy --add-section=.llvm.lto=%t/a-fatLTO.bc %t/a-fatLTO.o +; RUN: llvm-objcopy --set-section-flags=.llvm.lto=readonly,exclude %t/a-fatLTO.o +; RUN: llvm-readobj -S %t/a-fatLTO.o | FileCheck --check-prefix=CHECK-A %s + +; CHECK-A: Name: .llvm.lto + +; RUN: llc %t/main-LTO.ll --filetype=obj -o %t/main-fatLTO.o +; RUN: opt --module-summary %t/main-LTO.ll -o %t/main-fatLTO.bc +; RUN: llvm-objcopy --add-section=.llvm.lto=%t/main-fatLTO.bc %t/main-fatLTO.o +; RUN: llvm-objcopy --set-section-flags=.llvm.lto=readonly,exclude %t/main-fatLTO.o +; RUN: llvm-readobj -S %t/main-fatLTO.o | FileCheck --check-prefix=CHECK-MAIN %s + +; CHECK-MAIN: Name: .llvm.lto + +;; Final executable should not have .llvm.lto section no matter what the target is +; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext -o %t/foo-fatLTO %t/a-fatLTO.o %t/main-fatLTO.o +; RUN: llvm-readobj -S %t/foo-fatLTO | FileCheck --check-prefix=CHECK-LTO-TARGET %s + +;; Check that fat objects work w/ s=--start-lib +; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext -o %t/foo-fatLTO.start_lib --start-lib %t/a-fatLTO.o %t/main-fatLTO.o --end-lib +; RUN: llvm-readobj -S %t/foo-fatLTO.start_lib | FileCheck --check-prefix=CHECK-LTO-TARGET %s + +;; Check if .llvm.lto section gets aggregated in LTO target +; CHECK-LTO-TARGET-NOT: Name: .llvm.lto + +;; Final executable should not have .llvm.lto section no matter what the target is +; RUN: %gold -o %t/foo-fatNoLTO %t/a-fatLTO.o %/t/main-fatLTO.o +; RUN: llvm-readobj -S %t/foo-fatNoLTO | FileCheck --check-prefix=CHECK-NON-LTO-TARGET %s + +;; Check if .llvm.lto section gets aggregated in non-LTO target +; CHECK-NON-LTO-TARGET-NOT: Name: .llvm.lto + +;; Check if the LTO target executable produced from FatLTO object file is +;; identical to the one produced from LTO modules +; RUN: opt --module-summary %t/a-LTO.ll -o %t/a-LTO.bc +; RUN: opt --module-summary %t/main-LTO.ll -o %t/main-LTO.bc +; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext -o %t/foo-LTO %t/a-LTO.bc %t/main-LTO.bc +; RUN: cmp %t/foo-fatLTO %t/foo-LTO + +;; Check if the no-LTO target executable produced from FatLTO object file is +;; identical to the one produced from regular object files + +; RUN: llc %t/a-LTO.ll --filetype=obj -o %t/a.o +; RUN: llc %t/main-LTO.ll --filetype=obj -o %t/main.o + +; RUN: %gold -o %t/foo-noLTO %t/a.o %t/main.o +; RUN: cmp %t/foo-fatNoLTO %t/foo-noLTO + +;; Check archive support +; RUN: llvm-ar rcs %t/a.a %t/a-fatLTO.o +; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext -o %t/foo-fatLTO.archive %t/main-LTO.bc %t/a.a +; RUN: cmp %t/foo-fatLTO.archive %t/foo-LTO + +;--- a-LTO.ll +target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +; Function Attrs: noinline nounwind uwtable +define dso_local i32 @_start() #0 { +entry: + ret i32 0 +} + +attributes #0 = { noinline nounwind uwtable } + +!llvm.module.flags = !{!0, !1, !2, !3, !4, !5, !6} + +!0 = !{i32 1, !"wchar_size", i32 4} +!1 = !{i32 7, !"PIC Level", i32 2} +!2 = !{i32 7, !"PIE Level", i32 2} +!3 = !{i32 7, !"uwtable", i32 2} +!4 = !{i32 7, !"frame-pointer", i32 2} +!5 = !{i32 1, !"ThinLTO", i32 0} +!6 = !{i32 1, !"EnableSplitLTOUnit", i32 1} + +;--- main-LTO.ll +target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +; Function Attrs: noinline nounwind uwtable +define dso_local i32 @main() #0 { +entry: + %retval = alloca i32, align 4 + store i32 0, ptr %retval, align 4 + %call = call i32 (...) @_start() + ret i32 %call +} + +declare i32 @_start(...) + +attributes #0 = { noinline nounwind uwtable } + +!llvm.module.flags = !{!0, !1, !2, !3, !4, !5, !6} + +!0 = !{i32 1, !"wchar_size", i32 4} +!1 = !{i32 7, !"PIC Level", i32 2} +!2 = !{i32 7, !"PIE Level", i32 2} +!3 = !{i32 7, !"uwtable", i32 2} +!4 = !{i32 7, !"frame-pointer", i32 2} +!5 = !{i32 1, !"ThinLTO", i32 0} +!6 = !{i32 1, !"EnableSplitLTOUnit", i32 1} diff --git a/llvm/tools/gold/gold-plugin.cpp b/llvm/tools/gold/gold-plugin.cpp --- a/llvm/tools/gold/gold-plugin.cpp +++ b/llvm/tools/gold/gold-plugin.cpp @@ -538,14 +538,6 @@ BufferRef = Buffer->getMemBufferRef(); } - // Only use bitcode files for LTO. InputFile::create() will load bitcode - // from the .llvmbc section within a binary object, this bitcode is typically - // generated by -fembed-bitcode and is not to be used by LLVMgold.so for LTO. - if (identify_magic(BufferRef.getBuffer()) != file_magic::bitcode) { - *claimed = 0; - return LDPS_OK; - } - *claimed = 1; Expected> ObjOrErr = InputFile::create(BufferRef);