[mips] Expand JAL instructions when PIC is enabled.

[oota-llvm.git] / lib / Target / Mips / AsmParser / MipsAsmParser.cpp

diff --git a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index 54649fa7080d4f0d7494442ea7556fdd4476bbc0..45115ee0e1b89e22726ad956238f5f19af9ff7fe 100644 (file)
--- a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -1318,6 +1318,44 @@ static bool hasShortDelaySlot(unsigned Opcode) {
   }
 }
 
+static const MCSymbol *getSingleMCSymbol(const MCExpr *Expr) {
+  if (const MCSymbolRefExpr *SRExpr = dyn_cast<MCSymbolRefExpr>(Expr)) {
+    return &SRExpr->getSymbol();
+  }
+
+  if (const MCBinaryExpr *BExpr = dyn_cast<MCBinaryExpr>(Expr)) {
+    const MCSymbol *LHSSym = getSingleMCSymbol(BExpr->getLHS());
+    const MCSymbol *RHSSym = getSingleMCSymbol(BExpr->getRHS());
+
+    if (LHSSym)
+      return LHSSym;
+
+    if (RHSSym)
+      return RHSSym;
+
+    return nullptr;
+  }
+
+  if (const MCUnaryExpr *UExpr = dyn_cast<MCUnaryExpr>(Expr))
+    return getSingleMCSymbol(UExpr->getSubExpr());
+
+  return nullptr;
+}
+
+static unsigned countMCSymbolRefExpr(const MCExpr *Expr) {
+  if (isa<MCSymbolRefExpr>(Expr))
+    return 1;
+
+  if (const MCBinaryExpr *BExpr = dyn_cast<MCBinaryExpr>(Expr))
+    return countMCSymbolRefExpr(BExpr->getLHS()) +
+           countMCSymbolRefExpr(BExpr->getRHS());
+
+  if (const MCUnaryExpr *UExpr = dyn_cast<MCUnaryExpr>(Expr))
+    return countMCSymbolRefExpr(UExpr->getSubExpr());
+
+  return 0;
+}
+
 bool MipsAsmParser::processInstruction(MCInst &Inst, SMLoc IDLoc,
                                        SmallVectorImpl<MCInst> &Instructions) {
   const MCInstrDesc &MCID = getInstDesc(Inst.getOpcode());
@@ -1468,6 +1506,94 @@ bool MipsAsmParser::processInstruction(MCInst &Inst, SMLoc IDLoc,
     }
   }
 
+  // This expansion is not in a function called by expandInstruction() because
+  // the pseudo-instruction doesn't have a distinct opcode.
+  if ((Inst.getOpcode() == Mips::JAL || Inst.getOpcode() == Mips::JAL_MM) &&
+      inPicMode()) {
+    warnIfNoMacro(IDLoc);
+
+    const MCExpr *JalExpr = Inst.getOperand(0).getExpr();
+
+    // We can do this expansion if there's only 1 symbol in the argument
+    // expression.
+    if (countMCSymbolRefExpr(JalExpr) > 1)
+      return Error(IDLoc, "jal doesn't support multiple symbols in PIC mode");
+
+    // FIXME: This is checking the expression can be handled by the later stages
+    //        of the assembler. We ought to leave it to those later stages but
+    //        we can't do that until we stop evaluateRelocExpr() rewriting the
+    //        expressions into non-equivalent forms.
+    const MCSymbol *JalSym = getSingleMCSymbol(JalExpr);
+
+    // FIXME: Add support for label+offset operands (currently causes an error).
+    // FIXME: Add support for forward-declared local symbols.
+    // FIXME: Add expansion for when the LargeGOT option is enabled.
+    if (JalSym->isInSection() || JalSym->isTemporary()) {
+      if (isABI_O32()) {
+        // If it's a local symbol and the O32 ABI is being used, we expand to:
+        //  lw    $25, 0($gp)
+        //    R_(MICRO)MIPS_GOT16  label
+        //  addiu $25, $25, 0
+        //    R_(MICRO)MIPS_LO16   label
+        //  jalr  $25
+        const MCExpr *Got16RelocExpr = evaluateRelocExpr(JalExpr, "got");
+        const MCExpr *Lo16RelocExpr = evaluateRelocExpr(JalExpr, "lo");
+
+        MCInst LwInst;
+        LwInst.setOpcode(Mips::LW);
+        LwInst.addOperand(MCOperand::createReg(Mips::T9));
+        LwInst.addOperand(MCOperand::createReg(Mips::GP));
+        LwInst.addOperand(MCOperand::createExpr(Got16RelocExpr));
+        Instructions.push_back(LwInst);
+
+        MCInst AddiuInst;
+        AddiuInst.setOpcode(Mips::ADDiu);
+        AddiuInst.addOperand(MCOperand::createReg(Mips::T9));
+        AddiuInst.addOperand(MCOperand::createReg(Mips::T9));
+        AddiuInst.addOperand(MCOperand::createExpr(Lo16RelocExpr));
+        Instructions.push_back(AddiuInst);
+      } else if (isABI_N32() || isABI_N64()) {
+        // If it's a local symbol and the N32/N64 ABIs are being used,
+        // we expand to:
+        //  lw/ld    $25, 0($gp)
+        //    R_(MICRO)MIPS_GOT_DISP  label
+        //  jalr  $25
+        const MCExpr *GotDispRelocExpr = evaluateRelocExpr(JalExpr, "got_disp");
+
+        MCInst LoadInst;
+        LoadInst.setOpcode(ABI.ArePtrs64bit() ? Mips::LD : Mips::LW);
+        LoadInst.addOperand(MCOperand::createReg(Mips::T9));
+        LoadInst.addOperand(MCOperand::createReg(Mips::GP));
+        LoadInst.addOperand(MCOperand::createExpr(GotDispRelocExpr));
+        Instructions.push_back(LoadInst);
+      }
+    } else {
+      // If it's an external/weak symbol, we expand to:
+      //  lw/ld    $25, 0($gp)
+      //    R_(MICRO)MIPS_CALL16  label
+      //  jalr  $25
+      const MCExpr *Call16RelocExpr = evaluateRelocExpr(JalExpr, "call16");
+
+      MCInst LoadInst;
+      LoadInst.setOpcode(ABI.ArePtrs64bit() ? Mips::LD : Mips::LW);
+      LoadInst.addOperand(MCOperand::createReg(Mips::T9));
+      LoadInst.addOperand(MCOperand::createReg(Mips::GP));
+      LoadInst.addOperand(MCOperand::createExpr(Call16RelocExpr));
+      Instructions.push_back(LoadInst);
+    }
+
+    MCInst JalrInst;
+    JalrInst.setOpcode(inMicroMipsMode() ? Mips::JALR_MM : Mips::JALR);
+    JalrInst.addOperand(MCOperand::createReg(Mips::RA));
+    JalrInst.addOperand(MCOperand::createReg(Mips::T9));
+
+    // FIXME: Add an R_(MICRO)MIPS_JALR relocation after the JALR.
+    // This relocation is supposed to be an optimization hint for the linker
+    // and is not necessary for correctness.
+
+    Inst = JalrInst;
+  }
+
   if (MCID.mayLoad() || MCID.mayStore()) {
     // Check the offset of memory operand, if it is a symbol
     // reference or immediate we may have to expand instructions.