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Remove incredibly confusing isBaseAddressKnownZero.

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When referring to a symbol in a dwarf section on ELF we should use

.long foo

instead of

.long foo - .debug_something

because ELF is unaware of the content of the sections and therefore needs
relocations. This has nothing to do with optimizing a -0.

llvm-svn: 231751
This commit is contained in:
Rafael Espindola 2015-03-10 04:11:52 +00:00
parent 9f3b858c2b
commit b021663a47
4 changed files with 2 additions and 18 deletions
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8
include/llvm/MC/MCSection.h
View File

@ -52,14 +52,6 @@ namespace llvm {
raw_ostream &OS,
const MCExpr *Subsection) 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
// "optimized nops" to fill instead of 0s.
virtual bool UseCodeAlign() const = 0;

6
include/llvm/MC/MCSectionELF.h
View File

@ -75,12 +75,6 @@ public:
bool UseCodeAlign() const override;
bool isVirtualSection() const override;
/// isBaseAddressKnownZero - We know that non-allocatable sections (like
/// debug info) have a base of zero.
bool isBaseAddressKnownZero() const override {
return (getFlags() & ELF::SHF_ALLOC) == 0;
}
static bool classof(const MCSection *S) {
return S->getVariant() == SV_ELF;
}

5
lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
View File

@ -179,9 +179,8 @@ void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
assert((!Label->isInSection() || &Label->getSection() == &Section) &&
"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()) {
// If the format uses relocations with dwarf, refer to the symbol directly.
if (MAI->doesDwarfUseRelocationsAcrossSections()) {
OutStreamer.EmitSymbolValue(Label, 4);
return;
}

1
lib/Target/NVPTX/NVPTXSection.h
View File

@ -36,7 +36,6 @@ public:
const MCExpr *Subsection) const override {}
/// Base address of PTX sections is zero.
bool isBaseAddressKnownZero() const override { return true; }
bool UseCodeAlign() const override { return false; }
bool isVirtualSection() const override { return false; }
};