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* Fix one more bug in PIC codegen: extra load is needed for *all* 

non-statics.
* Introduce new option to output zero-initialized data to .bss section.
This can reduce size of binaries. Enable it by default for ELF &
Cygwin/Mingw targets. Probably, Darwin should be also added.

llvm-svn: 33299
This commit is contained in:
Anton Korobeynikov 2007-01-17 10:33:08 +00:00
parent 38ee6519b7
commit 3f6d52834b
8 changed files with 58 additions and 17 deletions
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7
llvm/include/llvm/Target/TargetAsmInfo.h
View File

@ -38,6 +38,10 @@ namespace llvm {
/// DataSection - Section directive for standard data.
///
const char *DataSection; // Defaults to ".data".
/// BSSSection - Section directive for uninitialized data.
///
const char *BSSSection; // Default to ".bss".
/// AddressSize - Size of addresses used in file.
///
@ -313,6 +317,9 @@ namespace llvm {
const char *getDataSection() const {
return DataSection;
}
const char *getBSSSection() const {
return BSSSection;
}
unsigned getAddressSize() const {
return AddressSize;
}

2
llvm/include/llvm/Target/TargetOptions.h
View File

@ -54,6 +54,8 @@ namespace llvm {
/// generate libcalls to the software floating point library instead of
/// target FP instructions.
extern bool UseSoftFloat;
extern bool NoZerosInBSS;
} // End llvm namespace
#endif

1
llvm/lib/Target/TargetAsmInfo.cpp
View File

@ -19,6 +19,7 @@ using namespace llvm;
TargetAsmInfo::TargetAsmInfo() :
TextSection(".text"),
DataSection(".data"),
BSSSection(".bss"),
AddressSize(4),
NeedsSet(false),
MaxInstLength(4),

6
llvm/lib/Target/TargetMachine.cpp
View File

@ -28,6 +28,7 @@ namespace llvm {
bool UnsafeFPMath;
bool FiniteOnlyFPMathOption;
bool UseSoftFloat;
bool NoZerosInBSS;
Reloc::Model RelocationModel;
CodeModel::Model CMModel;
}
@ -61,6 +62,11 @@ namespace {
cl::desc("Generate software floating point library calls"),
cl::location(UseSoftFloat),
cl::init(false));
cl::opt<bool, true>
DontPlaceZerosInBSS("nozero-initialized-in-bss",
cl::desc("Don't place zero-initialized symbols into bss section"),
cl::location(NoZerosInBSS),
cl::init(false));
cl::opt<llvm::Reloc::Model, true>
DefRelocationModel(

25
llvm/lib/Target/X86/X86ATTAsmPrinter.cpp
View File

@ -323,22 +323,19 @@ void X86ATTAsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNo,
O << Offset;
if (isMemOp) {
if (isExt) {
if (Subtarget->isPICStyleGOT()) {
if (Subtarget->isPICStyleGOT()) {
if (Subtarget->GVRequiresExtraLoad(GV, TM, false))
O << "@GOT";
} else if (Subtarget->isPICStyleRIPRel()) {
O << "@GOTPCREL(%rip)";
} else if (Subtarget->is64Bit() && !NotRIPRel)
// Use rip when possible to reduce code size, except when
// index or base register are also part of the address. e.g.
// foo(%rip)(%rcx,%rax,4) is not legal
O << "(%rip)";
} else {
if (Subtarget->is64Bit() && !NotRIPRel)
O << "(%rip)";
else if (Subtarget->isPICStyleGOT())
else
O << "@GOTOFF";
}
} else
if (isExt && Subtarget->isPICStyleRIPRel())
O << "@GOTPCREL(%rip)";
else if (Subtarget->is64Bit() && !NotRIPRel)
// Use rip when possible to reduce code size, except when
// index or base register are also part of the address. e.g.
// foo(%rip)(%rcx,%rax,4) is not legal
O << "(%rip)";
}
return;

11
llvm/lib/Target/X86/X86AsmPrinter.cpp
View File

@ -28,6 +28,7 @@
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
static X86FunctionInfo calculateFunctionInfo(const Function *F,
@ -149,7 +150,10 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
O << "\t.zerofill __DATA__, __common, " << name << ", "
<< Size << ", " << Align;
} else {
SwitchToDataSection(TAI->getDataSection(), I);
if (!NoZerosInBSS && TAI->getBSSSection())
SwitchToDataSection(TAI->getBSSSection(), I);
else
SwitchToDataSection(TAI->getDataSection(), I);
if (TAI->getLCOMMDirective() != NULL) {
if (I->hasInternalLinkage()) {
O << TAI->getLCOMMDirective() << name << "," << Size;
@ -224,7 +228,10 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
SwitchToDataSection(SectionName.c_str());
} else {
SwitchToDataSection(TAI->getDataSection(), I);
if (C->isNullValue() && !NoZerosInBSS && TAI->getBSSSection())
SwitchToDataSection(TAI->getBSSSection(), I);
else
SwitchToDataSection(TAI->getDataSection(), I);
}
break;

6
llvm/lib/Target/X86/X86Subtarget.cpp
View File

@ -36,10 +36,14 @@ bool X86Subtarget::GVRequiresExtraLoad(const GlobalValue* GV,
bool isDirectCall) const
{
if (TM.getRelocationModel() != Reloc::Static)
if (isTargetDarwin() || isPICStyleGOT()) {
if (isTargetDarwin()) {
return (!isDirectCall &&
(GV->hasWeakLinkage() || GV->hasLinkOnceLinkage() ||
(GV->isExternal() && !GV->hasNotBeenReadFromBytecode())));
} else if (isPICStyleGOT()) {
// Extra load is needed for all non-statics.
return (!isDirectCall &&
(GV->isExternal() || !GV->hasInternalLinkage()));
} else if (isTargetCygMing() || isTargetWindows()) {
return (GV->hasDLLImportLinkage());
}

17
llvm/test/CodeGen/X86/test-pic-6.ll Normal file
View File

@ -0,0 +1,17 @@
; RUN: llvm-as < %s | llc -mtriple=i686-pc-linux-gnu -relocation-model=pic &&
; RUN: llvm-as < %s | llc -mtriple=i686-pc-linux-gnu -relocation-model=pic | grep _GLOBAL_OFFSET_TABLE_ &&
; RUN: llvm-as < %s | llc -mtriple=i686-pc-linux-gnu -relocation-model=pic | grep piclabel | wc -l | grep 3 &&
; RUN: llvm-as < %s | llc -mtriple=i686-pc-linux-gnu -relocation-model=pic | grep GOT | wc -l | grep 3
%ptr = global i32* null
%dst = global i32 0
%src = global i32 0
define void %foo() {
entry:
store i32* %dst, i32** %ptr
%tmp.s = load i32* %src
store i32 %tmp.s, i32* %dst
ret void
}