+
+ // Otherwise, emit the most general non-SIB encoding: [REG+disp32]
+ MCE.emitByte(ModRMByte(2, RegOpcodeField, BaseRegNo));
+ emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
+ return;
+ }
+
+ // Otherwise we need a SIB byte, so start by outputting the ModR/M byte first.
+ assert(IndexReg.getReg() != X86::ESP &&
+ IndexReg.getReg() != X86::RSP && "Cannot use ESP as index reg!");
+
+ bool ForceDisp32 = false;
+ bool ForceDisp8 = false;
+ if (BaseReg == 0) {
+ // If there is no base register, we emit the special case SIB byte with
+ // MOD=0, BASE=4, to JUST get the index, scale, and displacement.
+ MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
+ ForceDisp32 = true;
+ } else if (DispForReloc) {
+ // Emit the normal disp32 encoding.
+ MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
+ ForceDisp32 = true;
+ } else if (DispVal == 0 && BaseRegNo != N86::EBP) {
+ // Emit no displacement ModR/M byte
+ MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
+ } else if (isDisp8(DispVal)) {
+ // Emit the disp8 encoding...
+ MCE.emitByte(ModRMByte(1, RegOpcodeField, 4));
+ ForceDisp8 = true; // Make sure to force 8 bit disp if Base=EBP
+ } else {
+ // Emit the normal disp32 encoding...
+ MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
+ }
+
+ // Calculate what the SS field value should be...
+ static const unsigned SSTable[] = { ~0, 0, 1, ~0, 2, ~0, ~0, ~0, 3 };
+ unsigned SS = SSTable[Scale.getImm()];
+
+ if (BaseReg == 0) {
+ // Handle the SIB byte for the case where there is no base, see Intel
+ // Manual 2A, table 2-7. The displacement has already been output.
+ unsigned IndexRegNo;
+ if (IndexReg.getReg())
+ IndexRegNo = getX86RegNum(IndexReg.getReg());
+ else // Examples: [ESP+1*<noreg>+4] or [scaled idx]+disp32 (MOD=0,BASE=5)
+ IndexRegNo = 4;
+ emitSIBByte(SS, IndexRegNo, 5);
+ } else {
+ unsigned BaseRegNo = getX86RegNum(BaseReg);
+ unsigned IndexRegNo;
+ if (IndexReg.getReg())
+ IndexRegNo = getX86RegNum(IndexReg.getReg());
+ else
+ IndexRegNo = 4; // For example [ESP+1*<noreg>+4]
+ emitSIBByte(SS, IndexRegNo, BaseRegNo);
+ }
+
+ // Do we need to output a displacement?
+ if (ForceDisp8) {
+ emitConstant(DispVal, 1);
+ } else if (DispVal != 0 || ForceDisp32) {
+ emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);