MachO: allow each section to have a linker-private symbol
The upcoming ARM64 backend doesn't have section-relative relocations,
so we give each section its own symbol to provide this functionality.
Of course, it doesn't need to appear in the final executable, so
linker-private is the best kind for this purpose.
llvm-svn: 205081
diff --git a/llvm/lib/MC/MCAsmInfo.cpp b/llvm/lib/MC/MCAsmInfo.cpp
index c78d3d5..9667145 100644
--- a/llvm/lib/MC/MCAsmInfo.cpp
+++ b/llvm/lib/MC/MCAsmInfo.cpp
@@ -41,6 +41,7 @@
LabelSuffix = ":";
DebugLabelSuffix = ":";
PrivateGlobalPrefix = "L";
+ LinkerPrivateGlobalPrefix = "";
InlineAsmStart = "APP";
InlineAsmEnd = "NO_APP";
Code16Directive = ".code16";
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index fdedec1..73ffdc0 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -153,6 +153,13 @@
return GetOrCreateSymbol(Name.toStringRef(NameSV));
}
+MCSymbol *MCContext::CreateLinkerPrivateTempSymbol() {
+ SmallString<128> NameSV;
+ raw_svector_ostream(NameSV)
+ << MAI->getLinkerPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
+ return CreateSymbol(NameSV);
+}
+
MCSymbol *MCContext::CreateTempSymbol() {
SmallString<128> NameSV;
raw_svector_ostream(NameSV)
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index c932c3c..742f784 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -8,6 +8,8 @@
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCStreamer.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
@@ -31,18 +33,31 @@
class MCMachOStreamer : public MCObjectStreamer {
private:
+ /// LabelSections - true if each section change should emit a linker local
+ /// label for use in relocations for assembler local references. Obviates the
+ /// need for local relocations. False by default.
+ bool LabelSections;
+
+ /// HasSectionLabel - map of which sections have already had a non-local
+ /// label emitted to them. Used so we don't emit extraneous linker local
+ /// labels in the middle of the section.
+ DenseMap<const MCSection*, bool> HasSectionLabel;
+
void EmitInstToData(const MCInst &Inst, const MCSubtargetInfo &STI) override;
void EmitDataRegion(DataRegionData::KindTy Kind);
void EmitDataRegionEnd();
+
public:
MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB, raw_ostream &OS,
- MCCodeEmitter *Emitter)
- : MCObjectStreamer(Context, MAB, OS, Emitter) {}
+ MCCodeEmitter *Emitter, bool label)
+ : MCObjectStreamer(Context, MAB, OS, Emitter),
+ LabelSections(label) {}
/// @name MCStreamer Interface
/// @{
+ void ChangeSection(const MCSection *Sect, const MCExpr *Subsect) override;
void EmitLabel(MCSymbol *Symbol) override;
void EmitDebugLabel(MCSymbol *Symbol) override;
void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
@@ -94,6 +109,19 @@
} // end anonymous namespace.
+void MCMachOStreamer::ChangeSection(const MCSection *Section,
+ const MCExpr *Subsection) {
+ // Change the section normally.
+ MCObjectStreamer::ChangeSection(Section, Subsection);
+ // Output a linker-local symbol so we don't need section-relative local
+ // relocations. The linker hates us when we do that.
+ if (LabelSections && !HasSectionLabel[Section]) {
+ MCSymbol *Label = getContext().CreateLinkerPrivateTempSymbol();
+ EmitLabel(Label);
+ HasSectionLabel[Section] = true;
+ }
+}
+
void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
MCSymbol *EHSymbol) {
MCSymbolData &SD =
@@ -425,8 +453,9 @@
MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
raw_ostream &OS, MCCodeEmitter *CE,
- bool RelaxAll) {
- MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE);
+ bool RelaxAll,
+ bool LabelSections) {
+ MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE, LabelSections);
if (RelaxAll)
S->getAssembler().setRelaxAll(true);
return S;