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COFF: When generating code for LTO, use static reloc model on 32-bit x86.

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Fixes PR34306.

This is because it usually results in more compact code, and because
there are also known code generation bugs when using the PIC model
(see bug).

Based on a patch by Carlo Kok.

Differential Revision: https://reviews.llvm.org/D38769

llvm-svn: 315400
This commit is contained in:
Peter Collingbourne 2017-10-11 00:46:58 +00:00
parent 85b1da1dc4
commit 8a40a7b15c
2 changed files with 26 additions and 1 deletions
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8
lld/COFF/LTO.cpp
View File

@ -64,7 +64,13 @@ static void saveBuffer(StringRef Buffer, const Twine &Path) {
static std::unique_ptr<lto::LTO> createLTO() {
lto::Config Conf;
Conf.Options = InitTargetOptionsFromCodeGenFlags();
Conf.RelocModel = Reloc::PIC_;
// Use static reloc model on 32-bit x86 because it usually results in more
// compact code, and because there are also known code generation bugs when
// using the PIC model (see PR34306).
if (Config->Machine == COFF::IMAGE_FILE_MACHINE_I386)
Conf.RelocModel = Reloc::Static;
else
Conf.RelocModel = Reloc::PIC_;
Conf.DisableVerify = true;
Conf.DiagHandler = diagnosticHandler;
Conf.OptLevel = Config->LTOOptLevel;

19
lld/test/COFF/lto-reloc-model.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: llvm-as -o %t %s
; RUN: lld-link /entry:main /subsystem:console /out:%t.exe %t
; RUN: llvm-objdump -d %t.exe | FileCheck %s
target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
target triple = "i686-pc-windows-msvc"
@foo = thread_local global i8 0
module asm "__tls_index = 1"
module asm "__tls_array = 2"
define i8* @main() {
; CHECK: movl 1, %eax
; CHECK: movl %fs:2, %ecx
; CHECK: movl (%ecx,%eax,4), %eax
; CHECK: leal (%eax), %eax
ret i8* @foo
}