Golang RegCoder.TryAllocReg方法代码示例

// LoadOp makes sure that index gets zero-extended if it's a VarReg operand.
func (mach X86) LoadOp(code gen.RegCoder, oper uint16, index values.Operand, resultType types.T, offset uint32) (result values.Operand) {
	size := oper >> 8

	baseReg, indexReg, ownIndexReg, disp := mach.opMemoryAddress(code, size, index, offset)
	if ownIndexReg {
		defer code.FreeReg(types.I64, indexReg)
	}

	load := memoryLoads[uint8(oper)]

	targetReg, ok := code.TryAllocReg(resultType)
	if !ok {
		targetReg = regResult
	}

	result = values.TempRegOperand(resultType, targetReg, load.zeroExt)

	insnType := load.insnType
	if insnType == 0 {
		insnType = resultType
	}

	load.insn.opFromIndirect(code, insnType, targetReg, 0, indexReg, baseReg, disp)
	return
}

// OpGetGlobal must not update CPU's condition flags.
func (mach X86) OpGetGlobal(code gen.RegCoder, t types.T, offset int32) values.Operand {
	reg, ok := code.TryAllocReg(t)
	if !ok {
		reg = regResult
	}

	if t.Category() == types.Int {
		Mov.opFromIndirect(code, t, reg, 0, NoIndex, regMemoryBase, offset)
	} else {
		MovSSE.opFromIndirect(code, t, reg, 0, NoIndex, regMemoryBase, offset)
	}

	return values.TempRegOperand(t, reg, true)
}

func (mach X86) unaryIntOp(code gen.RegCoder, index uint8, x values.Operand) (result values.Operand) {
	if index == opers.IndexIntEqz {
		reg, _, own := mach.opBorrowMaybeScratchReg(code, x, false)
		if own {
			defer code.FreeReg(x.Type, reg)
		}

		Test.opFromReg(code, x.Type, reg, reg)
		return values.ConditionFlagsOperand(values.Eq)
	}

	var targetReg regs.R

	sourceReg, _, own := mach.opBorrowMaybeScratchReg(code, x, false)
	if own {
		targetReg = sourceReg
	} else {
		var ok bool

		targetReg, ok = code.TryAllocReg(x.Type)
		if !ok {
			targetReg = regResult
		}
	}

	result = values.TempRegOperand(x.Type, targetReg, true)

	insn := unaryIntInsns[index]

	switch index {
	case opers.IndexIntClz:
		insn.opFromReg(code, x.Type, regScratch, sourceReg)
		MovImm.opImm(code, x.Type, targetReg, -1)
		Cmove.opFromReg(code, x.Type, regScratch, targetReg)
		MovImm.opImm(code, x.Type, targetReg, (int32(x.Type.Size())<<3)-1)
		Sub.opFromReg(code, x.Type, targetReg, regScratch)

	case opers.IndexIntCtz:
		insn.opFromReg(code, x.Type, targetReg, sourceReg)
		MovImm.opImm(code, x.Type, regScratch, int32(x.Type.Size())<<3)
		Cmove.opFromReg(code, x.Type, targetReg, regScratch)

	case opers.IndexIntPopcnt:
		insn.opFromReg(code, x.Type, targetReg, sourceReg)
	}

	return
}

// opMaybeResultReg returns either the register of the given operand, or the
// reserved result register with the value of the operand.  The caller has
// exclusive ownership of the register.
func (mach X86) opMaybeResultReg(code gen.RegCoder, x values.Operand, preserveFlags bool) (reg regs.R, zeroExt bool) {
	if x.Storage == values.TempReg {
		reg = x.Reg()
		zeroExt = x.RegZeroExt()
	} else {
		var ok bool

		reg, ok = code.TryAllocReg(x.Type)
		if !ok {
			reg = regResult
		}

		if x.Storage != values.Nowhere {
			mach.OpMove(code, reg, x, preserveFlags)
			zeroExt = true
		}
	}
	return
}

func (mach X86) binaryDivmulOp(code gen.RegCoder, index uint8, a, b values.Operand) values.Operand {
	insn := binaryDivmulInsns[index]
	t := a.Type

	if b.Storage == values.Imm {
		value := b.ImmValue()

		switch {
		case value == -1:
			reg, _ := mach.opMaybeResultReg(code, a, false)
			Neg.opReg(code, t, reg)
			return values.TempRegOperand(t, reg, true)

		case insn.shiftImm.defined() && value > 0 && isPowerOfTwo(uint64(value)):
			reg, _ := mach.opMaybeResultReg(code, a, false)
			insn.shiftImm.op(code, t, reg, log2(uint64(value)))
			return values.TempRegOperand(t, reg, true)
		}
	}

	division := (index & opers.DivmulMul) == 0
	checkZero := true
	checkOverflow := true

	if b.Storage.IsReg() {
		if b.Reg() == regResult {
			newReg := regScratch

			if division {
				var ok bool

				// can't use scratch reg as divisor since it contains the dividend high bits
				newReg, ok = code.TryAllocReg(t)
				if !ok {
					// borrow a register which we don't need in this function
					MovMMX.opFromReg(code, types.I64, regScratchMMX, regTextBase)
					defer MovMMX.opToReg(code, types.I64, regTextBase, regScratchMMX)

					newReg = regTextBase
				}
			}

			Mov.opFromReg(code, t, newReg, regResult)
			b = values.RegOperand(true, t, newReg)
		}
	} else {
		if division && b.Storage == values.Imm {
			value := b.ImmValue()
			if value != 0 {
				checkZero = false
			}
			if value != -1 {
				checkOverflow = false
			}
		}

		reg, ok := code.TryAllocReg(t)
		if !ok {
			// borrow a register which we don't need in this function
			MovMMX.opFromReg(code, types.I64, regScratchMMX, regTextBase)
			defer MovMMX.opToReg(code, types.I64, regTextBase, regScratchMMX)

			reg = regTextBase
		}

		mach.OpMove(code, reg, b, true)
		b = values.RegOperand(true, t, reg)
	}

	mach.OpMove(code, regResult, a, false)

	remainder := (index & opers.DivmulRem) != 0

	var doNot links.L

	if division {
		if checkZero {
			mach.opCheckDivideByZero(code, t, b.Reg())
		}

		if a.Storage == values.Imm {
			value := a.ImmValue()
			if t.Size() == types.Size32 {
				if value != -0x80000000 {
					checkOverflow = false
				}
			} else {
				if value != -0x8000000000000000 {
					checkOverflow = false
				}
			}
		}

		signed := (index & opers.DivmulSign) != 0

		if signed && checkOverflow {
			var do links.L

			if remainder {
				Xor.opFromReg(code, types.I32, regScratch, regScratch) // moved to result at the end
//.........这里部分代码省略.........