+/// EmitFunctionBodyStart - Emit a global entry point prefix for ELFv2.
+void PPCLinuxAsmPrinter::EmitFunctionBodyStart() {
+ // In the ELFv2 ABI, in functions that use the TOC register, we need to
+ // provide two entry points. The ABI guarantees that when calling the
+ // local entry point, r2 is set up by the caller to contain the TOC base
+ // for this function, and when calling the global entry point, r12 is set
+ // up by the caller to hold the address of the global entry point. We
+ // thus emit a prefix sequence along the following lines:
+ //
+ // func:
+ // # global entry point
+ // addis r2,r12,(.TOC.-func)@ha
+ // addi r2,r2,(.TOC.-func)@l
+ // .localentry func, .-func
+ // # local entry point, followed by function body
+ //
+ // This ensures we have r2 set up correctly while executing the function
+ // body, no matter which entry point is called.
+ if (Subtarget.isELFv2ABI()
+ // Only do all that if the function uses r2 in the first place.
+ && !MF->getRegInfo().use_empty(PPC::X2)) {
+
+ MCSymbol *GlobalEntryLabel = OutContext.CreateTempSymbol();
+ OutStreamer.EmitLabel(GlobalEntryLabel);
+ const MCSymbolRefExpr *GlobalEntryLabelExp =
+ MCSymbolRefExpr::Create(GlobalEntryLabel, OutContext);
+
+ MCSymbol *TOCSymbol = OutContext.GetOrCreateSymbol(StringRef(".TOC."));
+ const MCExpr *TOCDeltaExpr =
+ MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create(TOCSymbol, OutContext),
+ GlobalEntryLabelExp, OutContext);
+
+ const MCExpr *TOCDeltaHi =
+ PPCMCExpr::CreateHa(TOCDeltaExpr, false, OutContext);
+ EmitToStreamer(OutStreamer, MCInstBuilder(PPC::ADDIS)
+ .addReg(PPC::X2)
+ .addReg(PPC::X12)
+ .addExpr(TOCDeltaHi));
+
+ const MCExpr *TOCDeltaLo =
+ PPCMCExpr::CreateLo(TOCDeltaExpr, false, OutContext);
+ EmitToStreamer(OutStreamer, MCInstBuilder(PPC::ADDI)
+ .addReg(PPC::X2)
+ .addReg(PPC::X2)
+ .addExpr(TOCDeltaLo));
+
+ MCSymbol *LocalEntryLabel = OutContext.CreateTempSymbol();
+ OutStreamer.EmitLabel(LocalEntryLabel);
+ const MCSymbolRefExpr *LocalEntryLabelExp =
+ MCSymbolRefExpr::Create(LocalEntryLabel, OutContext);
+ const MCExpr *LocalOffsetExp =
+ MCBinaryExpr::CreateSub(LocalEntryLabelExp,
+ GlobalEntryLabelExp, OutContext);
+
+ PPCTargetStreamer *TS =
+ static_cast<PPCTargetStreamer *>(OutStreamer.getTargetStreamer());
+
+ if (TS)
+ TS->emitLocalEntry(CurrentFnSym, LocalOffsetExp);
+ }
+}
+