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Put each jump table in an independent section if the function is too.

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This allows the linker to GC both, fixing pr22557.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228937 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2015-02-12 17:16:46 +00:00
parent a858be4291
commit 8eeedf74d3
7 changed files with 100 additions and 6 deletions
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4
include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
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@ -56,6 +56,10 @@ public:
SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const override;
const MCSection *
getSectionForJumpTable(const Function &F, Mangler &Mang,
const TargetMachine &TM) const override;
/// Return an MCExpr to use for a reference to the specified type info global
/// variable from exception handling information.
const MCExpr *

4
include/llvm/Target/TargetLoweringObjectFile.h
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@ -94,6 +94,10 @@ public:
return SectionForGlobal(GV, getKindForGlobal(GV, TM), Mang, TM);
}
virtual const MCSection *
getSectionForJumpTable(const Function &F, Mangler &Mang,
const TargetMachine &TM) const;
/// Targets should implement this method to assign a section to globals with
/// an explicit section specfied. The implementation of this method can
/// assume that GV->hasSection() is true.

7
lib/CodeGen/AsmPrinter/AsmPrinter.cpp
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@ -1177,6 +1177,7 @@ void AsmPrinter::EmitJumpTableInfo() {
// Pick the directive to use to print the jump table entries, and switch to
// the appropriate section.
const Function *F = MF->getFunction();
const TargetLoweringObjectFile &TLOF = getObjFileLowering();
bool JTInDiffSection = false;
if (// In PIC mode, we need to emit the jump table to the same section as the
// function body itself, otherwise the label differences won't make sense.
@ -1187,13 +1188,11 @@ void AsmPrinter::EmitJumpTableInfo() {
// FIXME: this isn't the right predicate, should be based on the MCSection
// for the function.
F->isWeakForLinker()) {
OutStreamer.SwitchSection(
getObjFileLowering().SectionForGlobal(F, *Mang, TM));
OutStreamer.SwitchSection(TLOF.SectionForGlobal(F, *Mang, TM));
} else {
// Otherwise, drop it in the readonly section.
const MCSection *ReadOnlySection =
getObjFileLowering().getSectionForConstant(SectionKind::getReadOnly(),
/*C=*/nullptr);
TLOF.getSectionForJumpTable(*F, *Mang, TM);
OutStreamer.SwitchSection(ReadOnlySection);
JTInDiffSection = true;
}

22
lib/CodeGen/TargetLoweringObjectFileImpl.cpp
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@ -334,6 +334,28 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
return DataRelROSection;
}
const MCSection *TargetLoweringObjectFileELF::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;
SmallString<128> Name(".rodata.");
TM.getNameWithPrefix(Name, &F, Mang, true);
unsigned Flags = ELF::SHF_ALLOC;
StringRef Group = "";
if (C) {
Flags |= ELF::SHF_GROUP;
Group = C->getName();
}
return getContext().getELFSection(Name, ELF::SHT_PROGBITS, Flags, 0, Group);
}
/// getSectionForConstant - Given a mergeable constant with the
/// specified size and relocation information, return a section that it
/// should be placed in.

5
lib/Target/TargetLoweringObjectFile.cpp
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@ -270,6 +270,11 @@ SectionForGlobal(const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
return SelectSectionForGlobal(GV, Kind, Mang, TM);
}
const MCSection *TargetLoweringObjectFile::getSectionForJumpTable(
const Function &F, Mangler &Mang, const TargetMachine &TM) const {
return getSectionForConstant(SectionKind::getReadOnly(), /*C=*/nullptr);
}
/// getSectionForConstant - Given a mergable constant with the
/// specified size and relocation information, return a section that it
/// should be placed in.

33
test/CodeGen/X86/global-sections-comdat.ll
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@ -1,5 +1,36 @@
; RUN: llc < %s -mtriple=i386-unknown-linux | FileCheck %s -check-prefix=LINUX
; RUN: llc < %s -mtriple=i386-unknown-linux -data-sections | FileCheck %s -check-prefix=LINUX-SECTIONS
; RUN: llc < %s -mtriple=i386-unknown-linux -data-sections -function-sections | FileCheck %s -check-prefix=LINUX-SECTIONS
$F1 = comdat any
define void @F1(i32 %y) comdat {
bb0:
switch i32 %y, label %bb5 [
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 4, label %bb4
]
bb1:
ret void
bb2:
ret void
bb3:
ret void
bb4:
ret void
bb5:
ret void
}
; LINUX: .section .text.F1,"axG",@progbits,F1,comdat
; LINUX: .size F1,
; LINUX-NEXT: .cfi_endproc
; LINUX-NEXT: .section .rodata.F1,"aG",@progbits,F1,comdat
; LINUX-SECTIONS: .section .text.F1,"axG",@progbits,F1,comdat
; LINUX-SECTIONS: .size F1,
; LINUX-SECTIONS-NEXT: .cfi_endproc
; LINUX-SECTIONS-NEXT: .section .rodata.F1,"aG",@progbits,F1,comdat
$G16 = comdat any
@G16 = unnamed_addr constant i32 42, comdat

31
test/CodeGen/X86/global-sections.ll
View File

@ -2,7 +2,7 @@
; RUN: llc < %s -mtriple=i386-apple-darwin9.7 | FileCheck %s -check-prefix=DARWIN
; RUN: llc < %s -mtriple=i386-apple-darwin10 -relocation-model=static | FileCheck %s -check-prefix=DARWIN-STATIC
; RUN: llc < %s -mtriple=x86_64-apple-darwin10 | FileCheck %s -check-prefix=DARWIN64
; RUN: llc < %s -mtriple=i386-unknown-linux-gnu -data-sections | FileCheck %s -check-prefix=LINUX-SECTIONS
; RUN: llc < %s -mtriple=i386-unknown-linux-gnu -data-sections -function-sections | FileCheck %s -check-prefix=LINUX-SECTIONS
; RUN: llc < %s -mtriple=i686-pc-win32 -data-sections -function-sections | FileCheck %s -check-prefix=WIN32-SECTIONS
define void @F1() {
@ -12,6 +12,35 @@ define void @F1() {
; WIN32-SECTIONS: .section .text,"xr",one_only,_F1
; WIN32-SECTIONS: .globl _F1
define void @F2(i32 %y) {
bb0:
switch i32 %y, label %bb5 [
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 4, label %bb4
]
bb1:
ret void
bb2:
ret void
bb3:
ret void
bb4:
ret void
bb5:
ret void
}
; LINUX: .size F2,
; LINUX-NEX: .cfi_endproc
; LINUX-NEX: .section .rodata,"a",@progbits
; LINUX-SECTIONS: .section .text.F2,"ax",@progbits
; LINUX-SECTIONS: .size F2,
; LINUX-SECTIONS-NEXT: .cfi_endproc
; LINUX-SECTIONS-NEXT: .section .rodata.F2,"a",@progbits
; int G1;
@G1 = common global i32 0