plan9asm/arm_flags.go at main · goplus/plan9asm · GitHub

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package plan9asm

import (
	"fmt"
	"strings"
)

func (c *armCtx) storeFlag(slot string, v string) {
	fmt.Fprintf(c.b, "  store i1 %s, ptr %s\n", v, slot)
}

func (c *armCtx) storeFlagCond(cond, slot, v string) error {
	if cond == "" || strings.EqualFold(cond, "AL") {
		c.storeFlag(slot, v)
		return nil
	}
	cv, err := c.condValue(cond)
	if err != nil {
		return err
	}
	oldV := c.newTmp()
	sel := c.newTmp()
	fmt.Fprintf(c.b, "  %%%s = load i1, ptr %s\n", oldV, slot)
	fmt.Fprintf(c.b, "  %%%s = select i1 %s, i1 %s, i1 %%%s\n", sel, cv, v, oldV)
	c.storeFlag(slot, "%"+sel)
	return nil
}

func (c *armCtx) setFlagsSub(cond, dst, src, res string) error {
	c.flagsWritten = true
	z := c.newTmp()
	n := c.newTmp()
	carry := c.newTmp()
	fmt.Fprintf(c.b, "  %%%s = icmp eq i32 %s, 0\n", z, res)
	fmt.Fprintf(c.b, "  %%%s = icmp slt i32 %s, 0\n", n, res)
	fmt.Fprintf(c.b, "  %%%s = icmp uge i32 %s, %s\n", carry, dst, src)
	x1 := c.newTmp()
	x2 := c.newTmp()
	x3 := c.newTmp()
	ov := c.newTmp()
	fmt.Fprintf(c.b, "  %%%s = xor i32 %s, %s\n", x1, dst, src)
	fmt.Fprintf(c.b, "  %%%s = xor i32 %s, %s\n", x2, dst, res)
	fmt.Fprintf(c.b, "  %%%s = and i32 %%%s, %%%s\n", x3, x1, x2)
	fmt.Fprintf(c.b, "  %%%s = icmp slt i32 %%%s, 0\n", ov, x3)
	if err := c.storeFlagCond(cond, c.flagsZSlot, "%"+z); err != nil {
		return err
	}
	if err := c.storeFlagCond(cond, c.flagsNSlot, "%"+n); err != nil {
		return err
	}
	if err := c.storeFlagCond(cond, c.flagsCSlot, "%"+carry); err != nil {
		return err
	}
	return c.storeFlagCond(cond, c.flagsVSlot, "%"+ov)
}

func (c *armCtx) setFlagsAdd(cond, dst, src, res string) error {
	c.flagsWritten = true
	z := c.newTmp()
	n := c.newTmp()
	carry := c.newTmp()
	fmt.Fprintf(c.b, "  %%%s = icmp eq i32 %s, 0\n", z, res)
	fmt.Fprintf(c.b, "  %%%s = icmp slt i32 %s, 0\n", n, res)
	fmt.Fprintf(c.b, "  %%%s = icmp ult i32 %s, %s\n", carry, res, dst)
	x1 := c.newTmp()
	nx1 := c.newTmp()
	x2 := c.newTmp()
	x3 := c.newTmp()
	ov := c.newTmp()
	fmt.Fprintf(c.b, "  %%%s = xor i32 %s, %s\n", x1, dst, src)
	fmt.Fprintf(c.b, "  %%%s = xor i32 %%%s, -1\n", nx1, x1)
	fmt.Fprintf(c.b, "  %%%s = xor i32 %s, %s\n", x2, dst, res)
	fmt.Fprintf(c.b, "  %%%s = and i32 %%%s, %%%s\n", x3, nx1, x2)
	fmt.Fprintf(c.b, "  %%%s = icmp slt i32 %%%s, 0\n", ov, x3)
	if err := c.storeFlagCond(cond, c.flagsZSlot, "%"+z); err != nil {
		return err
	}
	if err := c.storeFlagCond(cond, c.flagsNSlot, "%"+n); err != nil {
		return err
	}
	if err := c.storeFlagCond(cond, c.flagsCSlot, "%"+carry); err != nil {
		return err
	}
	return c.storeFlagCond(cond, c.flagsVSlot, "%"+ov)
}

func (c *armCtx) setFlagsLogic(cond, res string) error {
	c.flagsWritten = true
	z := c.newTmp()
	n := c.newTmp()
	fmt.Fprintf(c.b, "  %%%s = icmp eq i32 %s, 0\n", z, res)
	fmt.Fprintf(c.b, "  %%%s = icmp slt i32 %s, 0\n", n, res)
	if err := c.storeFlagCond(cond, c.flagsZSlot, "%"+z); err != nil {
		return err
	}
	return c.storeFlagCond(cond, c.flagsNSlot, "%"+n)
}

func (c *armCtx) condValue(cond string) (string, error) {
	if !c.flagsWritten {
		return "", fmt.Errorf("arm: condition %s without any prior flags write", cond)
	}
	ldN := c.newTmp()
	ldZ := c.newTmp()
	ldC := c.newTmp()
	ldV := c.newTmp()
	fmt.Fprintf(c.b, "  %%%s = load i1, ptr %s\n", ldN, c.flagsNSlot)
	fmt.Fprintf(c.b, "  %%%s = load i1, ptr %s\n", ldZ, c.flagsZSlot)
	fmt.Fprintf(c.b, "  %%%s = load i1, ptr %s\n", ldC, c.flagsCSlot)
	fmt.Fprintf(c.b, "  %%%s = load i1, ptr %s\n", ldV, c.flagsVSlot)
	n := "%" + ldN
	z := "%" + ldZ
	carry := "%" + ldC
	v := "%" + ldV
	not := func(x string) string {
		t := c.newTmp()
		fmt.Fprintf(c.b, "  %%%s = xor i1 %s, true\n", t, x)
		return "%" + t
	}
	and := func(a, b string) string {
		t := c.newTmp()
		fmt.Fprintf(c.b, "  %%%s = and i1 %s, %s\n", t, a, b)
		return "%" + t
	}
	or := func(a, b string) string {
		t := c.newTmp()
		fmt.Fprintf(c.b, "  %%%s = or i1 %s, %s\n", t, a, b)
		return "%" + t
	}
	xor := func(a, b string) string {
		t := c.newTmp()
		fmt.Fprintf(c.b, "  %%%s = xor i1 %s, %s\n", t, a, b)
		return "%" + t
	}
	eq := func(a, b string) string {
		t := c.newTmp()
		fmt.Fprintf(c.b, "  %%%s = icmp eq i1 %s, %s\n", t, a, b)
		return "%" + t
	}
	switch strings.ToUpper(cond) {
	case "EQ":
		return z, nil
	case "NE":
		return not(z), nil
	case "CS", "HS":
		return carry, nil
	case "CC", "LO":
		return not(carry), nil
	case "HI":
		return and(carry, not(z)), nil
	case "LS":
		return or(not(carry), z), nil
	case "LT":
		return xor(n, v), nil
	case "GE":
		return eq(n, v), nil
	case "GT":
		return and(not(z), eq(n, v)), nil
	case "LE":
		return or(z, xor(n, v)), nil
	case "MI":
		return n, nil
	case "PL":
		return not(n), nil
	case "VS":
		return v, nil
	case "VC":
		return not(v), nil
	case "AL":
		return "true", nil
	default:
		return "", fmt.Errorf("arm: unsupported condition %q", cond)
	}
}