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[ELF] - Do not collect SHT_REL[A] sections unconditionally when --gc-sections and --emit-relocs used together. 

This is "Bug 34836 - --gc-sections remove relocations from --emit-relocs",

When --emit-relocs is used, LLD currently always drops SHT_REL[A] sections from
output if --gc-sections is present. Patch fixes the issue.

Differential revision: https://reviews.llvm.org/D38724

llvm-svn: 316418
This commit is contained in:
George Rimar 2017-10-24 08:26:32 +00:00
parent efd5177d5e
commit f4ca4a6fa1
3 changed files with 19 additions and 13 deletions
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4
lld/ELF/InputSection.h
View File

@ -237,8 +237,8 @@ public:
// Mark the piece at a given offset live. Used by GC.
void markLiveAt(uint64_t Offset) {
assert(this->Flags & llvm::ELF::SHF_ALLOC);
LiveOffsets.insert(Offset);
if (this->Flags & llvm::ELF::SHF_ALLOC)
LiveOffsets.insert(Offset);
}
// Translate an offset in the input section to an offset

12
lld/ELF/MarkLive.cpp
View File

@ -162,9 +162,9 @@ scanEhFrameSection(EhInputSection &EH,
scanEhFrameSection<ELFT>(EH, EH.template rels<ELFT>(), Fn);
}
// We do not garbage-collect two types of sections:
// 1) Sections used by the loader (.init, .fini, .ctors, .dtors or .jcr)
// 2) Non-allocatable sections which typically contain debugging information
// Some sections are used directly by the loader, so they should never be
// garbage-collected. This function returns true if a given section is such
// section.
template <class ELFT> static bool isReserved(InputSectionBase *Sec) {
switch (Sec->Type) {
case SHT_FINI_ARRAY:
@ -173,9 +173,6 @@ template <class ELFT> static bool isReserved(InputSectionBase *Sec) {
case SHT_PREINIT_ARRAY:
return true;
default:
if (!(Sec->Flags & SHF_ALLOC))
return true;
StringRef S = Sec->Name;
return S.startswith(".ctors") || S.startswith(".dtors") ||
S.startswith(".init") || S.startswith(".fini") ||
@ -198,9 +195,6 @@ template <class ELFT> static void doGcSections() {
if (Sec == &InputSection::Discarded)
return;
// We don't gc non alloc sections.
if (!(Sec->Flags & SHF_ALLOC))
return;
// Usually, a whole section is marked as live or dead, but in mergeable
// (splittable) sections, each piece of data has independent liveness bit.

16
lld/test/ELF/emit-relocs-gc.s
View File

@ -1,18 +1,30 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
## Show that we emit .rela.bar when GC is disabled.
## Show that we emit .rela.bar and .rela.text when GC is disabled.
# RUN: ld.lld --emit-relocs %t.o -o %t
# RUN: llvm-objdump %t -section-headers | FileCheck %s --check-prefix=NOGC
# NOGC: .rela.text
# NOGC: .rela.bar
## GC collects .bar section and we exclude .rela.bar from output.
## GC collects .bar section and we exclude .rela.bar from output. We keep
## .rela.text because we keep .text.
# RUN: ld.lld --gc-sections --emit-relocs --print-gc-sections %t.o -o %t \
# RUN: | FileCheck --check-prefix=MSG %s
# MSG: removing unused section from '.bar' in file
# MSG: removing unused section from '.rela.bar' in file
# RUN: llvm-objdump %t -section-headers | FileCheck %s --check-prefix=GC
# GC-NOT: rela.bar
# GC: rela.text
# GC-NOT: rela.bar
.section .bar,"a"
.quad .bar
.text
relocs:
.quad _start
.global _start
_start:
nop