[patch] Adjust behavior of FDE cross-section relocs for targets that don't support abs-differences.
Modern versions of OSX/Darwin's ld (ld64 > 97.17) have an optimisation present that allows the back end to omit relocations (and replace them with an absolute difference) for FDE some text section refs.
This patch allows a backend to opt-in to this behaviour by setting "DwarfFDESymbolsUseAbsDiff". At present, this is only enabled for modern x86 OSX ports.
test changes by David Fang.
llvm-svn: 198744
diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index 479f445..12070f3 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -839,8 +839,9 @@
}
}
-static void EmitSymbol(MCStreamer &streamer, const MCSymbol &symbol,
- unsigned symbolEncoding, const char *comment = 0) {
+static void EmitFDESymbol(MCStreamer &streamer, const MCSymbol &symbol,
+ unsigned symbolEncoding, bool isEH,
+ const char *comment = 0) {
MCContext &context = streamer.getContext();
const MCAsmInfo *asmInfo = context.getAsmInfo();
const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
@@ -848,7 +849,10 @@
streamer);
unsigned size = getSizeForEncoding(streamer, symbolEncoding);
if (streamer.isVerboseAsm() && comment) streamer.AddComment(comment);
- streamer.EmitAbsValue(v, size);
+ if (asmInfo->doDwarfFDESymbolsUseAbsDiff() && isEH)
+ streamer.EmitAbsValue(v, size);
+ else
+ streamer.EmitValue(v, size);
}
static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
@@ -1347,7 +1351,7 @@
unsigned PCEncoding = IsEH ? MOFI->getFDEEncoding(UsingCFI)
: (unsigned)dwarf::DW_EH_PE_absptr;
unsigned PCSize = getSizeForEncoding(streamer, PCEncoding);
- EmitSymbol(streamer, *frame.Begin, PCEncoding, "FDE initial location");
+ EmitFDESymbol(streamer, *frame.Begin, PCEncoding, IsEH, "FDE initial location");
// PC Range
const MCExpr *Range = MakeStartMinusEndExpr(streamer, *frame.Begin,
@@ -1367,8 +1371,8 @@
// Augmentation Data
if (frame.Lsda)
- EmitSymbol(streamer, *frame.Lsda, frame.LsdaEncoding,
- "Language Specific Data Area");
+ EmitFDESymbol(streamer, *frame.Lsda, frame.LsdaEncoding, true,
+ "Language Specific Data Area");
}
// Call Frame Instructions