github.com/reiver/go@v0.0.0-20150109200633-1d0c7792f172/src/runtime/sys_windows_amd64.s

// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"

// maxargs should be divisible by 2, as Windows stack
// must be kept 16-byte aligned on syscall entry.
#define maxargs 16

// void runtime·asmstdcall(void *c);
TEXT runtime·asmstdcall(SB),NOSPLIT,$0
	// asmcgocall will put first argument into CX.
	PUSHQ	CX			// save for later
	MOVQ	libcall_fn(CX), AX
	MOVQ	libcall_args(CX), SI
	MOVQ	libcall_n(CX), CX

	// SetLastError(0).
	MOVQ	0x30(GS), DI
	MOVL	$0, 0x68(DI)

	SUBQ	$(maxargs*8), SP	// room for args

	// Fast version, do not store args on the stack.
	CMPL	CX, $4
	JLE	loadregs

	// Check we have enough room for args.
	CMPL	CX, $maxargs
	JLE	2(PC)
	INT	$3			// not enough room -> crash

	// Copy args to the stack.
	MOVQ	SP, DI
	CLD
	REP; MOVSQ
	MOVQ	SP, SI

loadregs:
	// Load first 4 args into correspondent registers.
	MOVQ	0(SI), CX
	MOVQ	8(SI), DX
	MOVQ	16(SI), R8
	MOVQ	24(SI), R9

	// Call stdcall function.
	CALL	AX

	ADDQ	$(maxargs*8), SP

	// Return result.
	POPQ	CX
	MOVQ	AX, libcall_r1(CX)

	// GetLastError().
	MOVQ	0x30(GS), DI
	MOVL	0x68(DI), AX
	MOVQ	AX, libcall_err(CX)

	RET

TEXT runtime·badsignal2(SB),NOSPLIT,$48
	// stderr
	MOVQ	$-12, CX // stderr
	MOVQ	CX, 0(SP)
	MOVQ	runtime·_GetStdHandle(SB), AX
	CALL	AX

	MOVQ	AX, CX	// handle
	MOVQ	CX, 0(SP)
	MOVQ	$runtime·badsignalmsg(SB), DX // pointer
	MOVQ	DX, 8(SP)
	MOVL	$runtime·badsignallen(SB), R8 // count
	MOVQ	R8, 16(SP)
	LEAQ	40(SP), R9  // written count
	MOVQ	$0, 0(R9)
	MOVQ	R9, 24(SP)
	MOVQ	$0, 32(SP)	// overlapped
	MOVQ	runtime·_WriteFile(SB), AX
	CALL	AX
	
	RET

// faster get/set last error
TEXT runtime·getlasterror(SB),NOSPLIT,$0
	MOVQ	0x30(GS), AX
	MOVL	0x68(AX), AX
	MOVL	AX, ret+0(FP)
	RET

TEXT runtime·setlasterror(SB),NOSPLIT,$0
	MOVL	err+0(FP), AX
	MOVQ	0x30(GS),	CX
	MOVL	AX, 0x68(CX)
	RET

// Called by Windows as a Vectored Exception Handler (VEH).
// First argument is pointer to struct containing
// exception record and context pointers.
// Handler function is stored in AX.
// Return 0 for 'not handled', -1 for handled.
TEXT runtime·sigtramp(SB),NOSPLIT,$0-0
	// CX: PEXCEPTION_POINTERS ExceptionInfo

	// DI SI BP BX R12 R13 R14 R15 registers and DF flag are preserved
	// as required by windows callback convention.
	PUSHFQ
	SUBQ	$112, SP
	MOVQ	DI, 80(SP)
	MOVQ	SI, 72(SP)
	MOVQ	BP, 64(SP)
	MOVQ	BX, 56(SP)
	MOVQ	R12, 48(SP)
	MOVQ	R13, 40(SP)
	MOVQ	R14, 32(SP)
	MOVQ	R15, 88(SP)

	MOVQ	AX, R15	// save handler address

	// find g
	get_tls(DX)
	CMPQ	DX, $0
	JNE	3(PC)
	MOVQ	$0, AX // continue
	JMP	done
	MOVQ	g(DX), DX
	CMPQ	DX, $0
	JNE	2(PC)
	CALL	runtime·badsignal2(SB)

	// save g and SP in case of stack switch
	MOVQ	DX, 96(SP) // g
	MOVQ	SP, 104(SP)

	// do we need to switch to the g0 stack?
	MOVQ	g_m(DX), BX
	MOVQ	m_g0(BX), BX
	CMPQ	DX, BX
	JEQ	g0

	// switch to g0 stack
	get_tls(BP)
	MOVQ	BX, g(BP)
	MOVQ	(g_sched+gobuf_sp)(BX), DI
	// make it look like mstart called us on g0, to stop traceback
	SUBQ	$8, DI
	MOVQ	$runtime·mstart(SB), SI
	MOVQ	SI, 0(DI)
	// traceback will think that we've done PUSHFQ and SUBQ
	// on this stack, so subtract them here to match.
	// (we need room for sighandler arguments anyway).
	// and re-save old SP for restoring later.
	SUBQ	$(112+8), DI
	// save g, save old stack pointer.
	MOVQ	SP, 104(DI)
	MOVQ	DI, SP

g0:
	MOVQ	0(CX), BX // ExceptionRecord*
	MOVQ	8(CX), CX // Context*
	MOVQ	BX, 0(SP)
	MOVQ	CX, 8(SP)
	MOVQ	DX, 16(SP)
	CALL	R15	// call handler
	// AX is set to report result back to Windows
	MOVL	24(SP), AX

	// switch back to original stack and g
	// no-op if we never left.
	MOVQ	104(SP), SP
	MOVQ	96(SP), DX
	get_tls(BP)
	MOVQ	DX, g(BP)

done:
	// restore registers as required for windows callback
	MOVQ	88(SP), R15
	MOVQ	32(SP), R14
	MOVQ	40(SP), R13
	MOVQ	48(SP), R12
	MOVQ	56(SP), BX
	MOVQ	64(SP), BP
	MOVQ	72(SP), SI
	MOVQ	80(SP), DI
	ADDQ	$112, SP
	POPFQ

	RET

TEXT runtime·exceptiontramp(SB),NOSPLIT,$0
	MOVQ	$runtime·exceptionhandler(SB), AX
	JMP	runtime·sigtramp(SB)

TEXT runtime·firstcontinuetramp(SB),NOSPLIT,$0-0
	MOVQ	$runtime·firstcontinuehandler(SB), AX
	JMP	runtime·sigtramp(SB)

TEXT runtime·lastcontinuetramp(SB),NOSPLIT,$0-0
	MOVQ	$runtime·lastcontinuehandler(SB), AX
	JMP	runtime·sigtramp(SB)

TEXT runtime·ctrlhandler(SB),NOSPLIT,$8
	MOVQ	CX, 16(SP)		// spill
	MOVQ	$runtime·ctrlhandler1(SB), CX
	MOVQ	CX, 0(SP)
	CALL	runtime·externalthreadhandler(SB)
	RET

TEXT runtime·profileloop(SB),NOSPLIT,$8
	MOVQ	$runtime·profileloop1(SB), CX
	MOVQ	CX, 0(SP)
	CALL	runtime·externalthreadhandler(SB)
	RET

TEXT runtime·externalthreadhandler(SB),NOSPLIT,$0
	PUSHQ	BP
	MOVQ	SP, BP
	PUSHQ	BX
	PUSHQ	SI
	PUSHQ	DI
	PUSHQ	0x28(GS)
	MOVQ	SP, DX

	// setup dummy m, g
	SUBQ	$m__size, SP		// space for M
	MOVQ	SP, 0(SP)
	MOVQ	$m__size, 8(SP)
	CALL	runtime·memclr(SB)	// smashes AX,BX,CX

	LEAQ	m_tls(SP), CX
	MOVQ	CX, 0x28(GS)
	MOVQ	SP, BX
	SUBQ	$g__size, SP		// space for G
	MOVQ	SP, g(CX)
	MOVQ	SP, m_g0(BX)

	MOVQ	SP, 0(SP)
	MOVQ	$g__size, 8(SP)
	CALL	runtime·memclr(SB)	// smashes AX,BX,CX
	LEAQ	g__size(SP), BX
	MOVQ	BX, g_m(SP)

	LEAQ	-8192(SP), CX
	MOVQ	CX, (g_stack+stack_lo)(SP)
	ADDQ	$const__StackGuard, CX
	MOVQ	CX, g_stackguard0(SP)
	MOVQ	CX, g_stackguard1(SP)
	MOVQ	DX, (g_stack+stack_hi)(SP)

	PUSHQ	32(BP)			// arg for handler
	CALL	16(BP)
	POPQ	CX

	get_tls(CX)
	MOVQ	g(CX), CX
	MOVQ	(g_stack+stack_hi)(CX), SP
	POPQ	0x28(GS)
	POPQ	DI
	POPQ	SI
	POPQ	BX
	POPQ	BP
	RET

GLOBL runtime·cbctxts(SB), NOPTR, $8

TEXT runtime·callbackasm1(SB),NOSPLIT,$0
	// Construct args vector for cgocallback().
	// By windows/amd64 calling convention first 4 args are in CX, DX, R8, R9
	// args from the 5th on are on the stack.
	// In any case, even if function has 0,1,2,3,4 args, there is reserved
	// but uninitialized "shadow space" for the first 4 args.
	// The values are in registers.
  	MOVQ	CX, (16+0)(SP)
  	MOVQ	DX, (16+8)(SP)
  	MOVQ	R8, (16+16)(SP)
  	MOVQ	R9, (16+24)(SP)

	// remove return address from stack, we are not returning there
  	MOVQ	0(SP), AX
	ADDQ	$8, SP

	// determine index into runtime·cbctxts table
	MOVQ	$runtime·callbackasm(SB), DX
	SUBQ	DX, AX
	MOVQ	$0, DX
	MOVQ	$5, CX	// divide by 5 because each call instruction in runtime·callbacks is 5 bytes long
	DIVL	CX,

	// find correspondent runtime·cbctxts table entry
	MOVQ	runtime·cbctxts(SB), CX
	MOVQ	-8(CX)(AX*8), AX

	// extract callback context
	MOVQ	wincallbackcontext_argsize(AX), DX
	MOVQ	wincallbackcontext_gobody(AX), AX

	// preserve whatever's at the memory location that
	// the callback will use to store the return value
	LEAQ	8(SP), CX       // args vector, skip return address
	PUSHQ	0(CX)(DX*1)     // store 8 bytes from just after the args array
	ADDQ	$8, DX          // extend argsize by size of return value

	// DI SI BP BX R12 R13 R14 R15 registers and DF flag are preserved
	// as required by windows callback convention.
	PUSHFQ
	SUBQ	$64, SP
	MOVQ	DI, 56(SP)
	MOVQ	SI, 48(SP)
	MOVQ	BP, 40(SP)
	MOVQ	BX, 32(SP)
	MOVQ	R12, 24(SP)
	MOVQ	R13, 16(SP)
	MOVQ	R14, 8(SP)
	MOVQ	R15, 0(SP)

	// prepare call stack.  use SUBQ to hide from stack frame checks
	// cgocallback(Go func, void *frame, uintptr framesize)
	SUBQ	$24, SP
	MOVQ	DX, 16(SP)	// argsize (including return value)
	MOVQ	CX, 8(SP)	// callback parameters
	MOVQ	AX, 0(SP)	// address of target Go function
	CLD
	CALL	runtime·cgocallback_gofunc(SB)
	MOVQ	0(SP), AX
	MOVQ	8(SP), CX
	MOVQ	16(SP), DX
	ADDQ	$24, SP

	// restore registers as required for windows callback
	MOVQ	0(SP), R15
	MOVQ	8(SP), R14
	MOVQ	16(SP), R13
	MOVQ	24(SP), R12
	MOVQ	32(SP), BX
	MOVQ	40(SP), BP
	MOVQ	48(SP), SI
	MOVQ	56(SP), DI
	ADDQ	$64, SP
	POPFQ

	MOVL	-8(CX)(DX*1), AX  // return value
	POPQ	-8(CX)(DX*1)      // restore bytes just after the args
	RET

// uint32 tstart_stdcall(M *newm);
TEXT runtime·tstart_stdcall(SB),NOSPLIT,$0
	// CX contains first arg newm
	MOVQ	m_g0(CX), DX		// g

	// Layout new m scheduler stack on os stack.
	MOVQ	SP, AX
	MOVQ	AX, (g_stack+stack_hi)(DX)
	SUBQ	$(64*1024), AX		// stack size
	MOVQ	AX, (g_stack+stack_lo)(DX)
	ADDQ	$const__StackGuard, AX
	MOVQ	AX, g_stackguard0(DX)
	MOVQ	AX, g_stackguard1(DX)

	// Set up tls.
	LEAQ	m_tls(CX), SI
	MOVQ	SI, 0x28(GS)
	MOVQ	CX, g_m(DX)
	MOVQ	DX, g(SI)

	// Someday the convention will be D is always cleared.
	CLD

	CALL	runtime·stackcheck(SB)	// clobbers AX,CX
	CALL	runtime·mstart(SB)

	XORL	AX, AX			// return 0 == success
	RET

// set tls base to DI
TEXT runtime·settls(SB),NOSPLIT,$0
	MOVQ	DI, 0x28(GS)
	RET

// Sleep duration is in 100ns units.
TEXT runtime·usleep1(SB),NOSPLIT,$0
	MOVL	usec+0(FP), BX
	MOVQ	$runtime·usleep2(SB), AX // to hide from 6l

	// Execute call on m->g0 stack, in case we are not actually
	// calling a system call wrapper, like when running under WINE.
	get_tls(R15)
	CMPQ	R15, $0
	JNE	3(PC)
	// Not a Go-managed thread. Do not switch stack.
	CALL	AX
	RET

	MOVQ	g(R15), R13
	MOVQ	g_m(R13), R13

	// leave pc/sp for cpu profiler
	MOVQ	(SP), R12
	MOVQ	R12, m_libcallpc(R13)
	MOVQ	g(R15), R12
	MOVQ	R12, m_libcallg(R13)
	// sp must be the last, because once async cpu profiler finds
	// all three values to be non-zero, it will use them
	LEAQ	usec+0(FP), R12
	MOVQ	R12, m_libcallsp(R13)

	MOVQ	m_g0(R13), R14
	CMPQ	g(R15), R14
	JNE	switch
	// executing on m->g0 already
	CALL	AX
	JMP	ret

switch:
	// Switch to m->g0 stack and back.
	MOVQ	(g_sched+gobuf_sp)(R14), R14
	MOVQ	SP, -8(R14)
	LEAQ	-8(R14), SP
	CALL	AX
	MOVQ	0(SP), SP

ret:
	MOVQ	$0, m_libcallsp(R13)
	RET

// Runs on OS stack. duration (in 100ns units) is in BX.
TEXT runtime·usleep2(SB),NOSPLIT,$16
	MOVQ	SP, AX
	ANDQ	$~15, SP	// alignment as per Windows requirement
	MOVQ	AX, 8(SP)
	// Want negative 100ns units.
	NEGQ	BX
	MOVQ	SP, R8 // ptime
	MOVQ	BX, (R8)
	MOVQ	$-1, CX // handle
	MOVQ	$0, DX // alertable
	MOVQ	runtime·_NtWaitForSingleObject(SB), AX
	CALL	AX
	MOVQ	8(SP), SP
	RET

// func now() (sec int64, nsec int32)
TEXT time·now(SB),NOSPLIT,$8-12
	CALL	runtime·unixnano(SB)
	MOVQ	0(SP), AX

	// generated code for
	//	func f(x uint64) (uint64, uint64) { return x/1000000000, x%100000000 }
	// adapted to reduce duplication
	MOVQ	AX, CX
	MOVQ	$1360296554856532783, AX
	MULQ	CX
	ADDQ	CX, DX
	RCRQ	$1, DX
	SHRQ	$29, DX
	MOVQ	DX, sec+0(FP)
	IMULQ	$1000000000, DX
	SUBQ	DX, CX
	MOVL	CX, nsec+8(FP)
	RET