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139 строки
5.3 KiB
Diff
139 строки
5.3 KiB
Diff
From 8482662676a4b6ef79a718c8c09943cb15241664 Mon Sep 17 00:00:00 2001
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From: Tom Stellard <tstellar@redhat.com>
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Date: Tue, 21 Jun 2022 22:22:11 -0700
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Subject: [PATCH] [gold] Ignore bitcode from sections inside object files
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-fembed-bitcode will put bitcode into special sections within object
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files, but this is not meant to be used by LTO, so the gold plugin
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should ignore it.
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https://github.com/llvm/llvm-project/issues/47216
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Reviewed By: tejohnson, MaskRay
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Differential Revision: https://reviews.llvm.org/D116995
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---
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llvm/docs/BitCodeFormat.rst | 3 ++-
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llvm/docs/GoldPlugin.rst | 4 ++++
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.../tools/gold/X86/Inputs/bcsection-lib.ll | 6 +++++
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llvm/test/tools/gold/X86/Inputs/bcsection.s | 5 ++++
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llvm/test/tools/gold/X86/bcsection.ll | 23 +++++++++++++++----
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llvm/tools/gold/gold-plugin.cpp | 8 +++++++
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6 files changed, 43 insertions(+), 6 deletions(-)
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create mode 100644 llvm/test/tools/gold/X86/Inputs/bcsection-lib.ll
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diff --git a/llvm/docs/BitCodeFormat.rst b/llvm/docs/BitCodeFormat.rst
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index 8e81a7daa459..df1f6915d7d5 100644
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--- a/llvm/docs/BitCodeFormat.rst
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+++ b/llvm/docs/BitCodeFormat.rst
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@@ -475,7 +475,8 @@ formats. This wrapper format is useful for accommodating LTO in compilation
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pipelines where intermediate objects must be native object files which contain
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metadata in other sections.
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-Not all tools support this format.
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+Not all tools support this format. For example, lld and the gold plugin will
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+ignore these sections when linking object files.
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.. _encoding of LLVM IR:
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diff --git a/llvm/docs/GoldPlugin.rst b/llvm/docs/GoldPlugin.rst
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index ce310bc2cf3c..07d2fc203eba 100644
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--- a/llvm/docs/GoldPlugin.rst
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+++ b/llvm/docs/GoldPlugin.rst
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@@ -17,6 +17,10 @@ and above also supports LTO via plugins. However, usage of the LLVM
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gold plugin with ld.bfd is not tested and therefore not officially
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supported or recommended.
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+As of LLVM 15, the gold plugin will ignore bitcode from the ``.llvmbc``
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+section inside of ELF object files. However, LTO with bitcode files
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+is still supported.
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+
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.. _`gold linker`: http://sourceware.org/binutils
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.. _`GCC LTO`: http://gcc.gnu.org/wiki/LinkTimeOptimization
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.. _`gold plugin interface`: http://gcc.gnu.org/wiki/whopr/driver
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diff --git a/llvm/test/tools/gold/X86/Inputs/bcsection-lib.ll b/llvm/test/tools/gold/X86/Inputs/bcsection-lib.ll
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new file mode 100644
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index 000000000000..ef3557c19cdc
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--- /dev/null
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+++ b/llvm/test/tools/gold/X86/Inputs/bcsection-lib.ll
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@@ -0,0 +1,6 @@
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+declare void @elf_func()
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+
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+define i32 @lib_func() {
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+ call void @elf_func()
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+ ret i32 0
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+}
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diff --git a/llvm/test/tools/gold/X86/Inputs/bcsection.s b/llvm/test/tools/gold/X86/Inputs/bcsection.s
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index ede1e5c532dd..c523612563b4 100644
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--- a/llvm/test/tools/gold/X86/Inputs/bcsection.s
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+++ b/llvm/test/tools/gold/X86/Inputs/bcsection.s
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@@ -1,2 +1,7 @@
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+.global elf_func
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+
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+elf_func:
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+ ret
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+
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.section .llvmbc
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.incbin "bcsection.bc"
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diff --git a/llvm/test/tools/gold/X86/bcsection.ll b/llvm/test/tools/gold/X86/bcsection.ll
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index 6d3481f8f966..09882d83fe91 100644
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--- a/llvm/test/tools/gold/X86/bcsection.ll
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+++ b/llvm/test/tools/gold/X86/bcsection.ll
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@@ -2,16 +2,29 @@
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; RUN: llvm-as -o %t/bcsection.bc %s
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; RUN: llvm-mc -I=%t -filetype=obj -triple=x86_64-unknown-unknown -o %t/bcsection.bco %p/Inputs/bcsection.s
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-; RUN: llvm-nm --no-llvm-bc %t/bcsection.bco 2>&1 | FileCheck %s -check-prefix=NO-SYMBOLS
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-; NO-SYMBOLS: no symbols
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+; RUN: llc -filetype=obj -mtriple=x86_64-unknown-unknown -o %t/bcsection-lib.o %p/Inputs/bcsection-lib.ll
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-; RUN: %gold -r -o %t/bcsection.o -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold%shlibext %t/bcsection.bco
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-; RUN: llvm-nm --no-llvm-bc %t/bcsection.o | FileCheck %s
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+; RUN: %gold -shared --no-undefined -o %t/bcsection.so -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold%shlibext %t/bcsection.bco %t/bcsection-lib.o
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+
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+; This test checks that the gold plugin does not attempt to use the bitcode
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+; in the .llvmbc section for LTO. bcsection-lib.o calls a function that is
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+; present the symbol table of bcsection.bco, but not included in the embedded
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+; bitcode. If the linker were to use the bitcode, then the symbols in the
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+; symbol table of bcsection.bco will be ignored and the link will fail.
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+;
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+; bcsection.bco:
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+; .text:
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+; elf_func
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+; .llvmbc:
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+; bitcode_func
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+;
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+; bcsection-lib.o:
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+; calls elf_func()
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-unknown"
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; CHECK: main
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-define i32 @main() {
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+define i32 @bitcode_func() {
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ret i32 0
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}
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diff --git a/llvm/tools/gold/gold-plugin.cpp b/llvm/tools/gold/gold-plugin.cpp
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index 180c181368e3..294c7a3d6178 100644
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--- a/llvm/tools/gold/gold-plugin.cpp
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+++ b/llvm/tools/gold/gold-plugin.cpp
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@@ -540,6 +540,14 @@ static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
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BufferRef = Buffer->getMemBufferRef();
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}
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+ // Only use bitcode files for LTO. InputFile::create() will load bitcode
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+ // from the .llvmbc section within a binary object, this bitcode is typically
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+ // generated by -fembed-bitcode and is not to be used by LLVMgold.so for LTO.
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+ if (identify_magic(BufferRef.getBuffer()) != file_magic::bitcode) {
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+ *claimed = 0;
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+ return LDPS_OK;
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+ }
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+
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*claimed = 1;
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Expected<std::unique_ptr<InputFile>> ObjOrErr = InputFile::create(BufferRef);
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--
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2.37.1.1.g659da70093
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