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[LTO] Prevent asm references to be dropped from the output. 

Differential Revision:  https://reviews.llvm.org/D24617

llvm-svn: 281741
This commit is contained in:
Davide Italiano 2016-09-16 16:05:25 +00:00
parent 20d031948e
commit dc8e07b98e
2 changed files with 46 additions and 0 deletions
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18
llvm/lib/LTO/LTOBackend.cpp
View File

@ -25,6 +25,7 @@
#include "llvm/IR/PassManager.h"
#include "llvm/IR/Verifier.h"
#include "llvm/LTO/LTO.h"
#include "llvm/LTO/legacy/UpdateCompilerUsed.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Passes/PassBuilder.h"
#include "llvm/Support/Error.h"
@ -275,6 +276,19 @@ Expected<const Target *> initAndLookupTarget(Config &C, Module &Mod) {
}
static void handleAsmUndefinedRefs(Module &Mod, TargetMachine &TM) {
// Collect the list of undefined symbols used in asm and update
// llvm.compiler.used to prevent optimization to drop these from the output.
StringSet<> AsmUndefinedRefs;
object::IRObjectFile::CollectAsmUndefinedRefs(
Triple(Mod.getTargetTriple()), Mod.getModuleInlineAsm(),
[&AsmUndefinedRefs](StringRef Name, object::BasicSymbolRef::Flags Flags) {
if (Flags & object::BasicSymbolRef::SF_Undefined)
AsmUndefinedRefs.insert(Name);
});
updateCompilerUsed(Mod, TM, AsmUndefinedRefs);
}
Error lto::backend(Config &C, AddOutputFn AddOutput,
unsigned ParallelCodeGenParallelismLevel,
std::unique_ptr<Module> Mod) {
@ -285,6 +299,8 @@ Error lto::backend(Config &C, AddOutputFn AddOutput,
std::unique_ptr<TargetMachine> TM =
createTargetMachine(C, Mod->getTargetTriple(), *TOrErr);
handleAsmUndefinedRefs(*Mod, *TM);
if (!C.CodeGenOnly)
if (!opt(C, TM.get(), 0, *Mod, /*IsThinLto=*/false))
return Error();
@ -310,6 +326,8 @@ Error lto::thinBackend(Config &Conf, unsigned Task, AddOutputFn AddOutput,
std::unique_ptr<TargetMachine> TM =
createTargetMachine(Conf, Mod.getTargetTriple(), *TOrErr);
handleAsmUndefinedRefs(Mod, *TM);
if (Conf.CodeGenOnly) {
codegen(Conf, TM.get(), AddOutput, Task, Mod);
return Error();

28
llvm/test/tools/gold/X86/asm_undefined2.ll Normal file
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@ -0,0 +1,28 @@
; RegularLTO testcase
; RUN: llvm-as %s -o %t.o
; RUN: %gold -shared -m elf_x86_64 -o %t2 -plugin %llvmshlibdir/LLVMgold.so \
; RUN: %t.o --plugin-opt=save-temps -upatatino
; RUN: llvm-dis < %t2.0.5.precodegen.bc | FileCheck %s
; ThinLTO testcase
; RUN: opt -module-summary %s -o %t.o
; RUN: %gold -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold.so \
; RUN: --plugin-opt=save-temps \
; RUN: --plugin-opt=thinlto -o %t2 %t.o
; RUN: llvm-dis < %t.o.5.precodegen.bc | FileCheck %s
; Check that foo is properly appended to llvm.compiler.used
; CHECK: @llvm.compiler.used = appending global [1 x i8*] [i8* bitcast (void ()* @foo to i8*)], section "llvm.metadata"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
module asm ".global patatino"
module asm ".equ patatino, foo"
declare void @patatino()
define void @foo() {
call void @patatino()
ret void
}