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Put jump tables in unique sections on COFF.

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If a function is going in an unique section (because of -ffunction-sections
for example), putting a jump table in .rodata will keep .rodata alive and
that will keep alive any other function that also has a jump table.

Instead, put the jump table in a unique section that is associated with the
function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231961 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2015-03-11 19:58:37 +00:00
parent 52f83a9ab3
commit 0c78583bf6
3 changed files with 35 additions and 0 deletions
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4
include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
View File

@ -147,6 +147,10 @@ public:
SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const override;
const MCSection *
getSectionForJumpTable(const Function &F, Mangler &Mang,
const TargetMachine &TM) const override;
/// Extract the dependent library name from a linker option string. Returns
/// StringRef() if the option does not specify a library.
StringRef getDepLibFromLinkerOpt(StringRef LinkerOption) const override;

25
lib/CodeGen/TargetLoweringObjectFileImpl.cpp
View File

@ -948,6 +948,31 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
return DataSection;
}
const MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
const Function &F, Mangler &Mang, const TargetMachine &TM) const {
// If the function can be removed, produce a unique section so that
// the table doesn't prevent the removal.
const Comdat *C = F.getComdat();
bool EmitUniqueSection = TM.getFunctionSections() || C;
if (!EmitUniqueSection)
return ReadOnlySection;
// FIXME: we should produce a symbol for F instead.
if (F.hasPrivateLinkage())
return ReadOnlySection;
MCSymbol *Sym = TM.getSymbol(&F, Mang);
StringRef COMDATSymName = Sym->getName();
SectionKind Kind = SectionKind::getReadOnly();
const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
unsigned Characteristics = getCOFFSectionFlags(Kind);
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
}
StringRef TargetLoweringObjectFileCOFF::
getDepLibFromLinkerOpt(StringRef LinkerOption) const {
const char *LibCmd = "/DEFAULTLIB:";

6
test/CodeGen/X86/global-sections.ll
View File

@ -6,6 +6,7 @@
; RUN: llc < %s -mtriple=i386-unknown-linux-gnu -function-sections | FileCheck %s -check-prefix=LINUX-FUNC-SECTIONS
; RUN: llc < %s -mtriple=x86_64-pc-linux -data-sections -function-sections -relocation-model=pic | FileCheck %s -check-prefix=LINUX-SECTIONS-PIC
; RUN: llc < %s -mtriple=i686-pc-win32 -data-sections -function-sections | FileCheck %s -check-prefix=WIN32-SECTIONS
; RUN: llc < %s -mtriple=i686-pc-win32 -function-sections | FileCheck %s -check-prefix=WIN32-FUNC-SECTIONS
define void @F1() {
ret void
@ -48,6 +49,11 @@ bb5:
; LINUX-FUNC-SECTIONS-NEXT: .cfi_endproc
; LINUX-FUNC-SECTIONS-NEXT: .section .rodata.F2,"a",@progbits
; WIN32-FUNC-SECTIONS: .section .text,"xr",one_only,_F2
; WIN32-FUNC-SECTIONS-NOT: .section
; WIN32-FUNC-SECTIONS: .section .rdata,"dr",associative,_F2
; LINUX-SECTIONS-PIC: .section .text.F2,"ax",@progbits
; LINUX-SECTIONS-PIC: .size F2,
; LINUX-SECTIONS-PIC-NEXT: .cfi_endproc