src/pkg/runtime/asm_arm.s - go - Git at Google

 // Copyright 2009 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 "zasm_GOOS_GOARCH.h"

 // using frame size $-4 means do not save LR on stack.
 TEXT _rt0_arm(SB),7,$-4
 	MOVW	$0xcafebabe, R12

 	// copy arguments forward on an even stack
 	// use R13 instead of SP to avoid linker rewriting the offsets
 	MOVW	0(R13), R0		// argc
 	MOVW	$4(R13), R1		// argv
 	SUB	$64, R13		// plenty of scratch
 	AND	$~7, R13
 	MOVW	R0, 60(R13)		// save argc, argv away
 	MOVW	R1, 64(R13)

 	// set up m and g registers
 	// g is R10, m is R9
 	MOVW	$runtime·g0(SB), g
 	MOVW	$runtime·m0(SB), m

 	// save m->g0 = g0
 	MOVW	g, m_g0(m)

 	// create istack out of the OS stack
 	MOVW	$(-8192+104)(R13), R0
 	MOVW	R0, g_stackguard(g)	// (w 104b guard)
 	MOVW	R13, g_stackbase(g)
 	BL	runtime·emptyfunc(SB)	// fault if stack check is wrong

 	BL	runtime·check(SB)

 	// saved argc, argv
 	MOVW	60(R13), R0
 	MOVW	R0, 4(R13)
 	MOVW	64(R13), R1
 	MOVW	R1, 8(R13)
 	BL	runtime·args(SB)
 	BL	runtime·osinit(SB)
 	BL	runtime·schedinit(SB)

 	// create a new goroutine to start program
 	MOVW	$runtime·main(SB), R0
 	MOVW.W	R0, -4(R13)
 	MOVW	$8, R0
 	MOVW.W	R0, -4(R13)
 	MOVW	$0, R0
 	MOVW.W	R0, -4(R13)	// push $0 as guard
 	BL	runtime·newproc(SB)
 	MOVW	$12(R13), R13	// pop args and LR

 	// start this M
 	BL	runtime·mstart(SB)

 	MOVW	$1234, R0
 	MOVW	$1000, R1
 	MOVW	R0, (R1)	// fail hard
 	B	runtime·_dep_dummy(SB)	// Never reached

 // TODO(kaib): remove these once i actually understand how the linker removes symbols
 // pull in dummy dependencies
 TEXT runtime·_dep_dummy(SB),7,$0
 	BL	_div(SB)
 	BL	_divu(SB)
 	BL	_mod(SB)
 	BL	_modu(SB)
 	BL	_modu(SB)
 	BL	_sfloat(SB)

 TEXT runtime·breakpoint(SB),7,$0
 	// no breakpoint yet; let program exit
 	RET

 /*
  *  go-routine
  */

 // void gosave(Gobuf*)
 // save state in Gobuf; setjmp
 TEXT runtime·gosave(SB), 7, $-4
 	MOVW	0(FP), R0		// gobuf
 	MOVW	SP, gobuf_sp(R0)
 	MOVW	LR, gobuf_pc(R0)
 	MOVW	g, gobuf_g(R0)
 	RET

 // void gogo(Gobuf*, uintptr)
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB), 7, $-4
 	MOVW	0(FP), R1		// gobuf
 	MOVW	4(FP), R0		// return 2nd arg
 	MOVW	gobuf_g(R1), g
 	MOVW	0(g), R2		// make sure g != nil
 	MOVW	gobuf_sp(R1), SP	// restore SP
 	MOVW	gobuf_pc(R1), PC

 // void gogocall(Gobuf*, void (*fn)(void))
 // restore state from Gobuf but then call fn.
 // (call fn, returning to state in Gobuf)
 // using frame size $-4 means do not save LR on stack.
 TEXT runtime·gogocall(SB), 7, $-4
 	MOVW	0(FP), R0		// gobuf
 	MOVW	4(FP), R1		// fn
 	MOVW	8(FP), R2		// fp offset
 	MOVW	gobuf_g(R0), g
 	MOVW	0(g), R3		// make sure g != nil
 	MOVW	gobuf_sp(R0), SP	// restore SP
 	MOVW	gobuf_pc(R0), LR
 	MOVW	R1, PC

 // void mcall(void (*fn)(G*))
 // Switch to m->g0's stack, call fn(g).
 // Fn must never return.  It should gogo(&g->sched)
 // to keep running g.
 TEXT runtime·mcall(SB), 7, $-4
 	MOVW	fn+0(FP), R0

 	// Save caller state in g->gobuf.
 	MOVW	SP, (g_sched+gobuf_sp)(g)
 	MOVW	LR, (g_sched+gobuf_pc)(g)
 	MOVW	g, (g_sched+gobuf_g)(g)

 	// Switch to m->g0 & its stack, call fn.
 	MOVW	g, R1
 	MOVW	m_g0(m), g
 	CMP	g, R1
 	BL.EQ	runtime·badmcall(SB)
 	MOVW	(g_sched+gobuf_sp)(g), SP
 	SUB	$8, SP
 	MOVW	R1, 4(SP)
 	BL	(R0)
 	BL	runtime·badmcall2(SB)
 	RET

 /*
  * support for morestack
  */

 // Called during function prolog when more stack is needed.
 // R1 frame size
 // R2 arg size
 // R3 prolog's LR
 // NB. we do not save R0 because we've forced 5c to pass all arguments
 // on the stack.
 // using frame size $-4 means do not save LR on stack.
 TEXT runtime·morestack(SB),7,$-4
 	// Cannot grow scheduler stack (m->g0).
 	MOVW	m_g0(m), R4
 	CMP	g, R4
 	BL.EQ	runtime·abort(SB)

 	// Save in m.
 	MOVW	R1, m_moreframesize(m)
 	MOVW	R2, m_moreargsize(m)

 	// Called from f.
 	// Set m->morebuf to f's caller.
 	MOVW	R3, (m_morebuf+gobuf_pc)(m)	// f's caller's PC
 	MOVW	SP, (m_morebuf+gobuf_sp)(m)	// f's caller's SP
 	MOVW	$4(SP), R3			// f's argument pointer
 	MOVW	R3, m_moreargp(m)
 	MOVW	g, (m_morebuf+gobuf_g)(m)

 	// Set m->morepc to f's PC.
 	MOVW	LR, m_morepc(m)

 	// Call newstack on m->g0's stack.
 	MOVW	m_g0(m), g
 	MOVW	(g_sched+gobuf_sp)(g), SP
 	B	runtime·newstack(SB)

 // Called from reflection library.  Mimics morestack,
 // reuses stack growth code to create a frame
 // with the desired args running the desired function.
 //
 // func call(fn *byte, arg *byte, argsize uint32).
 TEXT reflect·call(SB), 7, $-4
 	// Save our caller's state as the PC and SP to
 	// restore when returning from f.
 	MOVW	LR, (m_morebuf+gobuf_pc)(m)	// our caller's PC
 	MOVW	SP, (m_morebuf+gobuf_sp)(m)	// our caller's SP
 	MOVW	g,  (m_morebuf+gobuf_g)(m)

 	// Set up morestack arguments to call f on a new stack.
 	// We set f's frame size to 1, as a hint to newstack
 	// that this is a call from reflect·call.
 	// If it turns out that f needs a larger frame than
 	// the default stack, f's usual stack growth prolog will
 	// allocate a new segment (and recopy the arguments).
 	MOVW	4(SP), R0			// fn
 	MOVW	8(SP), R1			// arg frame
 	MOVW	12(SP), R2			// arg size

 	MOVW	R0, m_morepc(m)			// f's PC
 	MOVW	R1, m_moreargp(m)		// f's argument pointer
 	MOVW	R2, m_moreargsize(m)		// f's argument size
 	MOVW	$1, R3
 	MOVW	R3, m_moreframesize(m)		// f's frame size

 	// Call newstack on m->g0's stack.
 	MOVW	m_g0(m), g
 	MOVW	(g_sched+gobuf_sp)(g), SP
 	B	runtime·newstack(SB)

 // Return point when leaving stack.
 // using frame size $-4 means do not save LR on stack.
 TEXT runtime·lessstack(SB), 7, $-4
 	// Save return value in m->cret
 	MOVW	R0, m_cret(m)

 	// Call oldstack on m->g0's stack.
 	MOVW	m_g0(m), g
 	MOVW	(g_sched+gobuf_sp)(g), SP
 	B	runtime·oldstack(SB)

 // void jmpdefer(fn, sp);
 // called from deferreturn.
 // 1. grab stored LR for caller
 // 2. sub 4 bytes to get back to BL deferreturn
 // 3. B to fn
 TEXT runtime·jmpdefer(SB), 7, $0
 	MOVW	0(SP), LR
 	MOVW	$-4(LR), LR	// BL deferreturn
 	MOVW	fn+0(FP), R0
 	MOVW	argp+4(FP), SP
 	MOVW	$-4(SP), SP	// SP is 4 below argp, due to saved LR
 	B		(R0)

 TEXT	runtime·asmcgocall(SB),7,$0
 	B	runtime·cgounimpl(SB)

 TEXT	runtime·cgocallback(SB),7,$0
 	B	runtime·cgounimpl(SB)

 TEXT runtime·memclr(SB),7,$20
 	MOVW	0(FP), R0
 	MOVW	$0, R1		// c = 0
 	MOVW	R1, -16(SP)
 	MOVW	4(FP), R1	// n
 	MOVW	R1, -12(SP)
 	MOVW	m, -8(SP)	// Save m and g
 	MOVW	g, -4(SP)
 	BL	runtime·memset(SB)
 	MOVW	-8(SP), m	// Restore m and g, memset clobbers them
 	MOVW	-4(SP), g
 	RET

 TEXT runtime·getcallerpc(SB),7,$-4
 	MOVW	0(SP), R0
 	RET

 TEXT runtime·setcallerpc(SB),7,$-4
 	MOVW	x+4(FP), R0
 	MOVW	R0, 0(SP)
 	RET

 TEXT runtime·getcallersp(SB),7,$-4
 	MOVW	0(FP), R0
 	MOVW	$-4(R0), R0
 	RET

 TEXT runtime·emptyfunc(SB),0,$0
 	RET

 // int64 runtime·cputicks(), so really
 // void runtime·cputicks(int64 *ticks)
 // stubbed: return int64(0)
 TEXT runtime·cputicks(SB),7,$0
 	MOVW    0(FP), R1
 	MOVW	$0, R0
 	MOVW    R0, 0(R1)
 	MOVW    R0, 4(R1)
 	RET

 TEXT runtime·abort(SB),7,$-4
 	MOVW	$0, R0
 	MOVW	(R0), R1

 // bool armcas(int32 *val, int32 old, int32 new)
 // Atomically:
 //	if(*val == old){
 //		*val = new;
 //		return 1;
 //	}else
 //		return 0;
 //
 // To implement runtime·cas in sys_$GOOS_arm.s
 // using the native instructions, use:
 //
 //	TEXT runtime·cas(SB),7,$0
 //		B	runtime·armcas(SB)
 //
 TEXT runtime·armcas(SB),7,$0
 	MOVW	valptr+0(FP), R1
 	MOVW	old+4(FP), R2
 	MOVW	new+8(FP), R3
 casl:
 	LDREX	(R1), R0
 	CMP		R0, R2
 	BNE		casfail
 	STREX	R3, (R1), R0
 	CMP		$0, R0
 	BNE		casl
 	MOVW	$1, R0
 	RET
 casfail:
 	MOVW	$0, R0
 	RET
	// Copyright 2009 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 "zasm_GOOS_GOARCH.h"

	// using frame size $-4 means do not save LR on stack.
	TEXT _rt0_arm(SB),7,$-4
	MOVW $0xcafebabe, R12

	// copy arguments forward on an even stack
	// use R13 instead of SP to avoid linker rewriting the offsets
	MOVW 0(R13), R0 // argc
	MOVW $4(R13), R1 // argv
	SUB $64, R13 // plenty of scratch
	AND $~7, R13
	MOVW R0, 60(R13) // save argc, argv away
	MOVW R1, 64(R13)

	// set up m and g registers
	// g is R10, m is R9
	MOVW $runtime·g0(SB), g
	MOVW $runtime·m0(SB), m

	// save m->g0 = g0
	MOVW g, m_g0(m)

	// create istack out of the OS stack
	MOVW $(-8192+104)(R13), R0
	MOVW R0, g_stackguard(g) // (w 104b guard)
	MOVW R13, g_stackbase(g)
	BL runtime·emptyfunc(SB) // fault if stack check is wrong

	BL runtime·check(SB)

	// saved argc, argv
	MOVW 60(R13), R0
	MOVW R0, 4(R13)
	MOVW 64(R13), R1
	MOVW R1, 8(R13)
	BL runtime·args(SB)
	BL runtime·osinit(SB)
	BL runtime·schedinit(SB)

	// create a new goroutine to start program
	MOVW $runtime·main(SB), R0
	MOVW.W R0, -4(R13)
	MOVW $8, R0
	MOVW.W R0, -4(R13)
	MOVW $0, R0
	MOVW.W R0, -4(R13) // push $0 as guard
	BL runtime·newproc(SB)
	MOVW $12(R13), R13 // pop args and LR

	// start this M
	BL runtime·mstart(SB)

	MOVW $1234, R0
	MOVW $1000, R1
	MOVW R0, (R1) // fail hard
	B runtime·_dep_dummy(SB) // Never reached

	// TODO(kaib): remove these once i actually understand how the linker removes symbols
	// pull in dummy dependencies
	TEXT runtime·_dep_dummy(SB),7,$0
	BL _div(SB)
	BL _divu(SB)
	BL _mod(SB)
	BL _modu(SB)
	BL _modu(SB)
	BL _sfloat(SB)

	TEXT runtime·breakpoint(SB),7,$0
	// no breakpoint yet; let program exit
	RET

	/*
	* go-routine
	*/

	// void gosave(Gobuf*)
	// save state in Gobuf; setjmp
	TEXT runtime·gosave(SB), 7, $-4
	MOVW 0(FP), R0 // gobuf
	MOVW SP, gobuf_sp(R0)
	MOVW LR, gobuf_pc(R0)
	MOVW g, gobuf_g(R0)
	RET

	// void gogo(Gobuf*, uintptr)
	// restore state from Gobuf; longjmp
	TEXT runtime·gogo(SB), 7, $-4
	MOVW 0(FP), R1 // gobuf
	MOVW 4(FP), R0 // return 2nd arg
	MOVW gobuf_g(R1), g
	MOVW 0(g), R2 // make sure g != nil
	MOVW gobuf_sp(R1), SP // restore SP
	MOVW gobuf_pc(R1), PC

	// void gogocall(Gobuf, void (fn)(void))
	// restore state from Gobuf but then call fn.
	// (call fn, returning to state in Gobuf)
	// using frame size $-4 means do not save LR on stack.
	TEXT runtime·gogocall(SB), 7, $-4
	MOVW 0(FP), R0 // gobuf
	MOVW 4(FP), R1 // fn
	MOVW 8(FP), R2 // fp offset
	MOVW gobuf_g(R0), g
	MOVW 0(g), R3 // make sure g != nil
	MOVW gobuf_sp(R0), SP // restore SP
	MOVW gobuf_pc(R0), LR
	MOVW R1, PC

	// void mcall(void (fn)(G))
	// Switch to m->g0's stack, call fn(g).
	// Fn must never return. It should gogo(&g->sched)
	// to keep running g.
	TEXT runtime·mcall(SB), 7, $-4
	MOVW fn+0(FP), R0

	// Save caller state in g->gobuf.
	MOVW SP, (g_sched+gobuf_sp)(g)
	MOVW LR, (g_sched+gobuf_pc)(g)
	MOVW g, (g_sched+gobuf_g)(g)

	// Switch to m->g0 & its stack, call fn.
	MOVW g, R1
	MOVW m_g0(m), g
	CMP g, R1
	BL.EQ runtime·badmcall(SB)
	MOVW (g_sched+gobuf_sp)(g), SP
	SUB $8, SP
	MOVW R1, 4(SP)
	BL (R0)
	BL runtime·badmcall2(SB)
	RET

	/*
	* support for morestack
	*/

	// Called during function prolog when more stack is needed.
	// R1 frame size
	// R2 arg size
	// R3 prolog's LR
	// NB. we do not save R0 because we've forced 5c to pass all arguments
	// on the stack.
	// using frame size $-4 means do not save LR on stack.
	TEXT runtime·morestack(SB),7,$-4
	// Cannot grow scheduler stack (m->g0).
	MOVW m_g0(m), R4
	CMP g, R4
	BL.EQ runtime·abort(SB)

	// Save in m.
	MOVW R1, m_moreframesize(m)
	MOVW R2, m_moreargsize(m)

	// Called from f.
	// Set m->morebuf to f's caller.
	MOVW R3, (m_morebuf+gobuf_pc)(m) // f's caller's PC
	MOVW SP, (m_morebuf+gobuf_sp)(m) // f's caller's SP
	MOVW $4(SP), R3 // f's argument pointer
	MOVW R3, m_moreargp(m)
	MOVW g, (m_morebuf+gobuf_g)(m)

	// Set m->morepc to f's PC.
	MOVW LR, m_morepc(m)

	// Call newstack on m->g0's stack.
	MOVW m_g0(m), g
	MOVW (g_sched+gobuf_sp)(g), SP
	B runtime·newstack(SB)

	// Called from reflection library. Mimics morestack,
	// reuses stack growth code to create a frame
	// with the desired args running the desired function.
	//
	// func call(fn byte, arg byte, argsize uint32).
	TEXT reflect·call(SB), 7, $-4
	// Save our caller's state as the PC and SP to
	// restore when returning from f.
	MOVW LR, (m_morebuf+gobuf_pc)(m) // our caller's PC
	MOVW SP, (m_morebuf+gobuf_sp)(m) // our caller's SP
	MOVW g, (m_morebuf+gobuf_g)(m)

	// Set up morestack arguments to call f on a new stack.
	// We set f's frame size to 1, as a hint to newstack
	// that this is a call from reflect·call.
	// If it turns out that f needs a larger frame than
	// the default stack, f's usual stack growth prolog will
	// allocate a new segment (and recopy the arguments).
	MOVW 4(SP), R0 // fn
	MOVW 8(SP), R1 // arg frame
	MOVW 12(SP), R2 // arg size

	MOVW R0, m_morepc(m) // f's PC
	MOVW R1, m_moreargp(m) // f's argument pointer
	MOVW R2, m_moreargsize(m) // f's argument size
	MOVW $1, R3
	MOVW R3, m_moreframesize(m) // f's frame size

	// Call newstack on m->g0's stack.
	MOVW m_g0(m), g
	MOVW (g_sched+gobuf_sp)(g), SP
	B runtime·newstack(SB)

	// Return point when leaving stack.
	// using frame size $-4 means do not save LR on stack.
	TEXT runtime·lessstack(SB), 7, $-4
	// Save return value in m->cret
	MOVW R0, m_cret(m)

	// Call oldstack on m->g0's stack.
	MOVW m_g0(m), g
	MOVW (g_sched+gobuf_sp)(g), SP
	B runtime·oldstack(SB)

	// void jmpdefer(fn, sp);
	// called from deferreturn.
	// 1. grab stored LR for caller
	// 2. sub 4 bytes to get back to BL deferreturn
	// 3. B to fn
	TEXT runtime·jmpdefer(SB), 7, $0
	MOVW 0(SP), LR
	MOVW $-4(LR), LR // BL deferreturn
	MOVW fn+0(FP), R0
	MOVW argp+4(FP), SP
	MOVW $-4(SP), SP // SP is 4 below argp, due to saved LR
	B (R0)

	TEXT runtime·asmcgocall(SB),7,$0
	B runtime·cgounimpl(SB)

	TEXT runtime·cgocallback(SB),7,$0
	B runtime·cgounimpl(SB)

	TEXT runtime·memclr(SB),7,$20
	MOVW 0(FP), R0
	MOVW $0, R1 // c = 0
	MOVW R1, -16(SP)
	MOVW 4(FP), R1 // n
	MOVW R1, -12(SP)
	MOVW m, -8(SP) // Save m and g
	MOVW g, -4(SP)
	BL runtime·memset(SB)
	MOVW -8(SP), m // Restore m and g, memset clobbers them
	MOVW -4(SP), g
	RET

	TEXT runtime·getcallerpc(SB),7,$-4
	MOVW 0(SP), R0
	RET

	TEXT runtime·setcallerpc(SB),7,$-4
	MOVW x+4(FP), R0
	MOVW R0, 0(SP)
	RET

	TEXT runtime·getcallersp(SB),7,$-4
	MOVW 0(FP), R0
	MOVW $-4(R0), R0
	RET

	TEXT runtime·emptyfunc(SB),0,$0
	RET

	// int64 runtime·cputicks(), so really
	// void runtime·cputicks(int64 *ticks)
	// stubbed: return int64(0)
	TEXT runtime·cputicks(SB),7,$0
	MOVW 0(FP), R1
	MOVW $0, R0
	MOVW R0, 0(R1)
	MOVW R0, 4(R1)
	RET

	TEXT runtime·abort(SB),7,$-4
	MOVW $0, R0
	MOVW (R0), R1

	// bool armcas(int32 *val, int32 old, int32 new)
	// Atomically:
	// if(*val == old){
	// *val = new;
	// return 1;
	// }else
	// return 0;
	//
	// To implement runtime·cas in sys_$GOOS_arm.s
	// using the native instructions, use:
	//
	// TEXT runtime·cas(SB),7,$0
	// B runtime·armcas(SB)
	//
	TEXT runtime·armcas(SB),7,$0
	MOVW valptr+0(FP), R1
	MOVW old+4(FP), R2
	MOVW new+8(FP), R3
	casl:
	LDREX (R1), R0
	CMP R0, R2
	BNE casfail
	STREX R3, (R1), R0
	CMP $0, R0
	BNE casl
	MOVW $1, R0
	RET
	casfail:
	MOVW $0, R0
	RET