[XRay][CodeGen] Use PIC-friendly code in XRay sleds and remove synthetic references in .text
Summary:
This is a re-roll of D36615 which uses PLT relocations in the back-end
to the call to __xray_CustomEvent() when building in -fPIC and
-fxray-instrument mode.
Reviewers: pcc, djasper, bkramer
Subscribers: sdardis, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D37373
llvm-svn: 312466
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 5e002e7..8739935 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2767,10 +2767,13 @@
Out->EmitSymbolValue(Sled, Bytes);
Out->EmitSymbolValue(CurrentFnSym, Bytes);
auto Kind8 = static_cast<uint8_t>(Kind);
- Out->EmitBytes(StringRef(reinterpret_cast<const char *>(&Kind8), 1));
- Out->EmitBytes(
+ Out->EmitBinaryData(StringRef(reinterpret_cast<const char *>(&Kind8), 1));
+ Out->EmitBinaryData(
StringRef(reinterpret_cast<const char *>(&AlwaysInstrument), 1));
- Out->EmitZeros(2 * Bytes - 2); // Pad the previous two entries
+ Out->EmitBinaryData(StringRef(reinterpret_cast<const char *>(&Version), 1));
+ auto Padding = (4 * Bytes) - ((2 * Bytes) + 3);
+ assert(Padding >= 0 && "Instrumentation map entry > 4 * Word Size");
+ Out->EmitZeros(Padding);
}
void AsmPrinter::emitXRayTable() {
@@ -2782,19 +2785,22 @@
MCSection *InstMap = nullptr;
MCSection *FnSledIndex = nullptr;
if (MF->getSubtarget().getTargetTriple().isOSBinFormatELF()) {
+ auto Associated = dyn_cast<MCSymbolELF>(PrevSection->getBeginSymbol());
+ assert(Associated != nullptr);
+ auto Flags = ELF::SHF_WRITE | ELF::SHF_ALLOC | ELF::SHF_LINK_ORDER;
+ std::string GroupName;
if (Fn->hasComdat()) {
- InstMap = OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS,
- ELF::SHF_ALLOC | ELF::SHF_GROUP, 0,
- Fn->getComdat()->getName());
- FnSledIndex = OutContext.getELFSection("xray_fn_idx", ELF::SHT_PROGBITS,
- ELF::SHF_ALLOC | ELF::SHF_GROUP, 0,
- Fn->getComdat()->getName());
- } else {
- InstMap = OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS,
- ELF::SHF_ALLOC);
- FnSledIndex = OutContext.getELFSection("xray_fn_idx", ELF::SHT_PROGBITS,
- ELF::SHF_ALLOC);
+ Flags |= ELF::SHF_GROUP;
+ GroupName = Fn->getComdat()->getName();
}
+
+ auto UniqueID = ++XRayFnUniqueID;
+ InstMap =
+ OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS, Flags, 0,
+ GroupName, UniqueID, Associated);
+ FnSledIndex =
+ OutContext.getELFSection("xray_fn_idx", ELF::SHT_PROGBITS, Flags, 0,
+ GroupName, UniqueID, Associated);
} else if (MF->getSubtarget().getTargetTriple().isOSBinFormatMachO()) {
InstMap = OutContext.getMachOSection("__DATA", "xray_instr_map", 0,
SectionKind::getReadOnlyWithRel());
@@ -2804,15 +2810,7 @@
llvm_unreachable("Unsupported target");
}
- // Before we switch over, we force a reference to a label inside the
- // xray_fn_idx sections. This makes sure that the xray_fn_idx section is kept
- // live by the linker if the function is not garbage-collected. Since this
- // function is always called just before the function's end, we assume that
- // this is happening after the last return instruction.
auto WordSizeBytes = MAI->getCodePointerSize();
- MCSymbol *IdxRef = OutContext.createTempSymbol("xray_fn_idx_synth_", true);
- OutStreamer->EmitCodeAlignment(16);
- OutStreamer->EmitSymbolValue(IdxRef, WordSizeBytes, false);
// Now we switch to the instrumentation map section. Because this is done
// per-function, we are able to create an index entry that will represent the
@@ -2831,15 +2829,14 @@
// pointers. This should work for both 32-bit and 64-bit platforms.
OutStreamer->SwitchSection(FnSledIndex);
OutStreamer->EmitCodeAlignment(2 * WordSizeBytes);
- OutStreamer->EmitLabel(IdxRef);
- OutStreamer->EmitSymbolValue(SledsStart, WordSizeBytes);
- OutStreamer->EmitSymbolValue(SledsEnd, WordSizeBytes);
+ OutStreamer->EmitSymbolValue(SledsStart, WordSizeBytes, false);
+ OutStreamer->EmitSymbolValue(SledsEnd, WordSizeBytes, false);
OutStreamer->SwitchSection(PrevSection);
Sleds.clear();
}
void AsmPrinter::recordSled(MCSymbol *Sled, const MachineInstr &MI,
- SledKind Kind) {
+ SledKind Kind, uint8_t Version) {
auto Fn = MI.getParent()->getParent()->getFunction();
auto Attr = Fn->getFnAttribute("function-instrument");
bool LogArgs = Fn->hasFnAttribute("xray-log-args");
@@ -2847,8 +2844,8 @@
Attr.isStringAttribute() && Attr.getValueAsString() == "xray-always";
if (Kind == SledKind::FUNCTION_ENTER && LogArgs)
Kind = SledKind::LOG_ARGS_ENTER;
- Sleds.emplace_back(
- XRayFunctionEntry{ Sled, CurrentFnSym, Kind, AlwaysInstrument, Fn });
+ Sleds.emplace_back(XRayFunctionEntry{Sled, CurrentFnSym, Kind,
+ AlwaysInstrument, Fn, Version});
}
uint16_t AsmPrinter::getDwarfVersion() const {