[PATCH] D48756: Add option for section ordering

[Bill Wendling via Phabricator via llvm-commits]

void created this revision.
void added a reviewer: tejohnson.
Herald added subscribers: llvm-commits, dexonsmith, mehdi_amini.

Not all programs want section ordering when compiled with LTO.
In particular, the Linux kernel is very sensitive when it comes to linking, and
doesn't boot when each function is placed in its own sections.


Repository:
  rL LLVM

https://reviews.llvm.org/D48756

Files:
  test/tools/gold/X86/multiple-data.s
  test/tools/gold/X86/multiple-sections.ll
  tools/gold/gold-plugin.cpp


Index: tools/gold/gold-plugin.cpp
===================================================================
--- tools/gold/gold-plugin.cpp
+++ tools/gold/gold-plugin.cpp
@@ -203,6 +203,8 @@
   static std::string dwo_dir;
   /// Statistics output filename.
   static std::string stats_file;
+  // Section ordering.
+  static bool section_ordering;
 
   // Optimization remarks filename and hotness options
   static std::string OptRemarksFilename;
@@ -278,6 +280,8 @@
       OptRemarksWithHotness = true;
     } else if (opt.startswith("stats-file=")) {
       stats_file = opt.substr(strlen("stats-file="));
+    } else if (opt == "section-ordering") {
+      section_ordering = true;
     } else {
       // Save this option to pass to the code generator.
       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
@@ -834,9 +838,8 @@
   // FIXME: Check the gold version or add a new option to enable them.
   Conf.Options.RelaxELFRelocations = false;
 
-  // Enable function/data sections by default.
-  Conf.Options.FunctionSections = true;
-  Conf.Options.DataSections = true;
+  Conf.Options.FunctionSections = options::section_ordering;
+  Conf.Options.DataSections = options::section_ordering;
 
   Conf.MAttrs = MAttrs;
   Conf.RelocModel = RelocationModel;
Index: test/tools/gold/X86/multiple-sections.ll
===================================================================
--- test/tools/gold/X86/multiple-sections.ll
+++ test/tools/gold/X86/multiple-sections.ll
@@ -3,6 +3,7 @@
 ; RUN: echo ".text.pat" >> %t_order_lto.txt
 ; RUN: llvm-as %s -o %t.o
 ; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext \
+; RUN:     -plugin-option=section-ordering \
 ; RUN:     -m elf_x86_64 -o %t.exe %t.o \
 ; RUN:     --section-ordering-file=%t_order_lto.txt
 ; RUN: llvm-readobj -elf-output-style=GNU -t %t.exe | FileCheck %s
Index: test/tools/gold/X86/multiple-data.s
===================================================================
--- test/tools/gold/X86/multiple-data.s
+++ test/tools/gold/X86/multiple-data.s
@@ -5,6 +5,7 @@
 # RUN: llvm-mc %s -o %t.o -filetype=obj -triple=x86_64-unknown-linux-gnu
 # RUN: llvm-as %p/Inputs/multiple-data.ll -o %t2.o
 # RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext \
+# RUN:     -plugin-opt=section-ordering \
 # RUN:     -m elf_x86_64 -o %t.exe %t2.o %t.o  \
 # RUN:     --section-ordering-file=%t_order_lto.txt
 # RUN: llvm-readobj -elf-output-style=GNU -t %t.exe | FileCheck %s


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