Reland r298901 with modifications (reverted in r298932)
Dont emit Mapping symbols for sections that contain only data.
Summary:
Dont emit mapping symbols for sections that contain only data.
Reviewers: rengolin, weimingz, kparzysz, t.p.northover, peter.smith
Reviewed By: t.p.northover
Patched by Shankar Easwaran <shankare@codeaurora.org>
Subscribers: alekseyshl, t.p.northover, llvm-commits
Differential Revision: https://reviews.llvm.org/D30724
llvm-svn: 299392
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
index f7bdda4..774a0b3 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
@@ -464,13 +464,14 @@
void emitUnwindRaw(int64_t Offset, const SmallVectorImpl<uint8_t> &Opcodes);
void ChangeSection(MCSection *Section, const MCExpr *Subsection) override {
- // We have to keep track of the mapping symbol state of any sections we
- // use. Each one should start off as EMS_None, which is provided as the
- // default constructor by DenseMap::lookup.
- LastMappingSymbols[getPreviousSection().first] = LastEMS;
- LastEMS = LastMappingSymbols.lookup(Section);
-
+ LastMappingSymbols[getPreviousSection().first] = std::move(LastEMSInfo);
MCELFStreamer::ChangeSection(Section, Subsection);
+ auto LastMappingSymbol = LastMappingSymbols.find(Section);
+ if (LastMappingSymbol != LastMappingSymbols.end()) {
+ LastEMSInfo = std::move(LastMappingSymbol->second);
+ return;
+ }
+ LastEMSInfo.reset(new ElfMappingSymbolInfo(SMLoc(), nullptr, 0));
}
/// This function is the one used to emit instruction data into the ELF
@@ -532,15 +533,25 @@
MCELFStreamer::EmitBytes(Data);
}
+ void FlushPendingMappingSymbol() {
+ if (!LastEMSInfo->hasInfo())
+ return;
+ ElfMappingSymbolInfo *EMS = LastEMSInfo.get();
+ EmitMappingSymbol("$d", EMS->Loc, EMS->F, EMS->Offset);
+ EMS->resetInfo();
+ }
+
/// This is one of the functions used to emit data into an ELF section, so the
/// ARM streamer overrides it to add the appropriate mapping symbol ($d) if
/// necessary.
void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override {
- if (const MCSymbolRefExpr *SRE = dyn_cast_or_null<MCSymbolRefExpr>(Value))
+ if (const MCSymbolRefExpr *SRE = dyn_cast_or_null<MCSymbolRefExpr>(Value)) {
if (SRE->getKind() == MCSymbolRefExpr::VK_ARM_SBREL && !(Size == 4)) {
getContext().reportError(Loc, "relocated expression must be 32-bit");
return;
}
+ getOrCreateDataFragment();
+ }
EmitDataMappingSymbol();
MCELFStreamer::EmitValueImpl(Value, Size, Loc);
@@ -573,22 +584,54 @@
EMS_Data
};
+ struct ElfMappingSymbolInfo {
+ explicit ElfMappingSymbolInfo(SMLoc Loc, MCFragment *F, uint64_t O)
+ : Loc(Loc), F(F), Offset(O), State(EMS_None) {}
+ void resetInfo() {
+ F = nullptr;
+ Offset = 0;
+ }
+ bool hasInfo() { return F != nullptr; }
+ SMLoc Loc;
+ MCFragment *F;
+ uint64_t Offset;
+ ElfMappingSymbol State;
+ };
+
void EmitDataMappingSymbol() {
- if (LastEMS == EMS_Data) return;
+ if (LastEMSInfo->State == EMS_Data)
+ return;
+ else if (LastEMSInfo->State == EMS_None) {
+ // This is a tentative symbol, it won't really be emitted until it's
+ // actually needed.
+ ElfMappingSymbolInfo *EMS = LastEMSInfo.get();
+ auto *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
+ if (!DF)
+ return;
+ EMS->Loc = SMLoc();
+ EMS->F = getCurrentFragment();
+ EMS->Offset = DF->getContents().size();
+ LastEMSInfo->State = EMS_Data;
+ return;
+ }
EmitMappingSymbol("$d");
- LastEMS = EMS_Data;
+ LastEMSInfo->State = EMS_Data;
}
void EmitThumbMappingSymbol() {
- if (LastEMS == EMS_Thumb) return;
+ if (LastEMSInfo->State == EMS_Thumb)
+ return;
+ FlushPendingMappingSymbol();
EmitMappingSymbol("$t");
- LastEMS = EMS_Thumb;
+ LastEMSInfo->State = EMS_Thumb;
}
void EmitARMMappingSymbol() {
- if (LastEMS == EMS_ARM) return;
+ if (LastEMSInfo->State == EMS_ARM)
+ return;
+ FlushPendingMappingSymbol();
EmitMappingSymbol("$a");
- LastEMS = EMS_ARM;
+ LastEMSInfo->State = EMS_ARM;
}
void EmitMappingSymbol(StringRef Name) {
@@ -601,6 +644,17 @@
Symbol->setExternal(false);
}
+ void EmitMappingSymbol(StringRef Name, SMLoc Loc, MCFragment *F,
+ uint64_t Offset) {
+ auto *Symbol = cast<MCSymbolELF>(getContext().getOrCreateSymbol(
+ Name + "." + Twine(MappingSymbolCounter++)));
+ EmitLabel(Symbol, Loc, F);
+ Symbol->setType(ELF::STT_NOTYPE);
+ Symbol->setBinding(ELF::STB_LOCAL);
+ Symbol->setExternal(false);
+ Symbol->setOffset(Offset);
+ }
+
void EmitThumbFunc(MCSymbol *Func) override {
getAssembler().setIsThumbFunc(Func);
EmitSymbolAttribute(Func, MCSA_ELF_TypeFunction);
@@ -626,8 +680,10 @@
bool IsThumb;
int64_t MappingSymbolCounter = 0;
- DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols;
- ElfMappingSymbol LastEMS = EMS_None;
+ DenseMap<const MCSection *, std::unique_ptr<ElfMappingSymbolInfo>>
+ LastMappingSymbols;
+
+ std::unique_ptr<ElfMappingSymbolInfo> LastEMSInfo;
// ARM Exception Handling Frame Information
MCSymbol *ExTab;