Speculatively revert commit 127478 (jsjodin) in an attempt to fix the

llvm-gcc-i386-linux-selfhost and llvm-x86_64-linux-checks buildbots.
The original log entry:
Remove optimization emitting a reference insted of label difference, since
it can create more relocations. Removed isBaseAddressKnownZero method,
because it is no longer used.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127540 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2011-03-12 13:07:37 +00:00
parent c5c03f9024
commit ba9934648f
3 changed files with 21 additions and 0 deletions

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@ -52,6 +52,14 @@ namespace llvm {
virtual void PrintSwitchToSection(const MCAsmInfo &MAI, virtual void PrintSwitchToSection(const MCAsmInfo &MAI,
raw_ostream &OS) const = 0; raw_ostream &OS) const = 0;
/// isBaseAddressKnownZero - Return true if we know that this section will
/// get a base address of zero. In cases where we know that this is true we
/// can emit section offsets as direct references to avoid a subtraction
/// from the base of the section, saving a relocation.
virtual bool isBaseAddressKnownZero() const {
return false;
}
// UseCodeAlign - Return true if a .align directive should use // UseCodeAlign - Return true if a .align directive should use
// "optimized nops" to fill instead of 0s. // "optimized nops" to fill instead of 0s.
virtual bool UseCodeAlign() const = 0; virtual bool UseCodeAlign() const = 0;

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@ -66,6 +66,12 @@ public:
virtual bool UseCodeAlign() const; virtual bool UseCodeAlign() const;
virtual bool isVirtualSection() const; virtual bool isVirtualSection() const;
/// isBaseAddressKnownZero - We know that non-allocatable sections (like
/// debug info) have a base of zero.
virtual bool isBaseAddressKnownZero() const {
return (getFlags() & ELF::SHF_ALLOC) == 0;
}
static bool classof(const MCSection *S) { static bool classof(const MCSection *S) {
return S->getVariant() == SV_ELF; return S->getVariant() == SV_ELF;
} }

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@ -191,6 +191,13 @@ void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
assert((!Label->isInSection() || &Label->getSection() == &Section) && assert((!Label->isInSection() || &Label->getSection() == &Section) &&
"Section offset using wrong section base for label"); "Section offset using wrong section base for label");
// If the section in question will end up with an address of 0 anyway, we can
// just emit an absolute reference to save a relocation.
if (Section.isBaseAddressKnownZero()) {
OutStreamer.EmitSymbolValue(Label, 4, 0/*AddrSpace*/);
return;
}
// Otherwise, emit it as a label difference from the start of the section. // Otherwise, emit it as a label difference from the start of the section.
EmitLabelDifference(Label, SectionLabel, 4); EmitLabelDifference(Label, SectionLabel, 4);
} }