* in %rdi, %rsi, %rdx.
 */
.globl EXT(crosscall1)
EXT(crosscall1):
	pushq %rbx
	pushq %rbp
	pushq %r12
	pushq %r13
	pushq %r14
	pushq %r15

#if defined(_WIN64)
	movq %r8, %rdi	/* arg of setg_gcc */
	call *%rdx	/* setg_gcc */
	call *%rcx	/* fn */
#else
	movq %rdi, %rbx
	movq %rdx, %rdi	/* arg of setg_gcc */
	call *%rsi	/* setg_gcc */
	call *%rbx	/* fn */

	c.r8 = c.rsp
	c.r9 = c.rip
}

func dumpregs(r *context) {
	print("rax     ", hex(r.rax), "\n")
	print("rbx     ", hex(r.rbx), "\n")
	print("rcx     ", hex(r.rcx), "\n")
	print("rdx     ", hex(r.rdx), "\n")
	print("rdi     ", hex(r.rdi), "\n")
	print("rsi     ", hex(r.rsi), "\n")
	print("rbp     ", hex(r.rbp), "\n")
	print("rsp     ", hex(r.rsp), "\n")
	print("r8      ", hex(r.r8), "\n")

}

func (c *sigctxt) rax() uint64 { return c.regs().rax }
func (c *sigctxt) rbx() uint64 { return c.regs().rbx }
func (c *sigctxt) rcx() uint64 { return c.regs().rcx }
func (c *sigctxt) rdx() uint64 { return c.regs().rdx }
func (c *sigctxt) rdi() uint64 { return c.regs().rdi }
func (c *sigctxt) rsi() uint64 { return c.regs().rsi }
func (c *sigctxt) rbp() uint64 { return c.regs().rbp }

	x := Mem{Base: Load(Param("x"), GP64())}
	y := Load(Param("y"), GP64())

	carry := GP64()
	XORQ(carry, carry) // zero out carry

	for i := 0; i < bits/64; i++ {
		Comment("Iteration " + strconv.Itoa(i))
		hi, lo := RDX, RAX // implicit MULQ inputs and outputs
		MOVQ(x.Offset(i*8), lo)
		MULQ(y)
		ADDQ(z.Offset(i*8), lo)
		ADCQ(Imm(0), hi)
		ADDQ(carry, lo)
		ADCQ(Imm(0), hi)
		MOVQ(hi, carry)
		MOVQ(lo, z.Offset(i*8))
	}

	"internal/abi"
	"internal/goarch"
	"unsafe"
)

func dumpregs(c *sigctxt) {
	print("rax    ", hex(c.rax()), "\n")
	print("rbx    ", hex(c.rbx()), "\n")
	print("rcx    ", hex(c.rcx()), "\n")
	print("rdx    ", hex(c.rdx()), "\n")
	print("rdi    ", hex(c.rdi()), "\n")
	print("rsi    ", hex(c.rsi()), "\n")
	print("rbp    ", hex(c.rbp()), "\n")
	print("rsp    ", hex(c.rsp()), "\n")
	print("r8     ", hex(c.r8()), "\n")

		Load(aX, RAX)
	case 2:
		Comment(fmt.Sprintf("%s = 2×%s×%s", r, aX, bX))
		Load(aX, RAX)
		SHLQ(Imm(1), RAX)
	default:
		panic("unsupported i value")
	}
	MULQ(mustAddr(bX)) // RDX, RAX = RAX * bX
	MOVQ(RAX, r.lo)
	MOVQ(RDX, r.hi)
}

// addMul64 sets r to r + i * aX * bX.
func addMul64(r uint128, i uint64, aX, bX namedComponent) {
	switch i {
	case 1:
		Comment(fmt.Sprintf("%s += %s×%s", r, aX, bX))

0x207f?zi
	sys·ifaces2i(31440, 0, 31480, ...)
	sys·ifaces2i(0x7ad0, 0x7af8, 0x0, ...)
0x136f?zi
	main·main(1, 0, 1606416424, ...)
	main·main(0x1, 0x7fff5fbff828, 0x0, ...)

rax     0x1
rbx     0x1
rcx     0x33b5
rdx     0x0
rdi     0x1
rsi     0x7684
rbp     0x7684
rsp     0xafb8
r8      0x0
r9      0x0
r10     0x1002
r11     0x206
r12     0x0
r13     0x0
r14     0x7c48
r15     0xa000
rip     0x1b7d

func (c *sigctxt) rax() uint64 { return c.regs().rax }
func (c *sigctxt) rbx() uint64 { return c.regs().rbx }
func (c *sigctxt) rcx() uint64 { return c.regs().rcx }
func (c *sigctxt) rdx() uint64 { return c.regs().rdx }
func (c *sigctxt) rdi() uint64 { return c.regs().rdi }
func (c *sigctxt) rsi() uint64 { return c.regs().rsi }
func (c *sigctxt) rbp() uint64 { return c.regs().rbp }

	R14      uint64
	R13      uint64
	R12      uint64
	Rbp      uint64
	Rbx      uint64
	R11      uint64
	R10      uint64
	R9       uint64
	R8       uint64
	Rax      uint64
	Rcx      uint64
	Rdx      uint64
	Rsi      uint64
	Rdi      uint64
	Orig_rax uint64
	Rip      uint64
	Cs       uint64
	Eflags   uint64
	Rsp      uint64
	Ss       uint64
	Fs_base  uint64
	Gs_base  uint64
	Ds       uint64

# x is rsi:rdi, y is rcx:rdx, return result is rdx:rax.
.globl __umodti3
__umodti3:
	# specialized to u128 % u64, so verify that
	test %rcx,%rcx
	jne 1f

	# save divisor
	movq %rdx, %r8

	# reduce top 64 bits mod divisor
	movq %rsi, %rax
	xorl %edx, %edx
	divq %r8

	# reduce full 128-bit mod divisor
	# quotient fits in 64 bits because top 64 bits have been reduced < divisor.