mirror of
https://github.com/tinygo-org/tinygo.git
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Ayke van Laethem
add014f21b
This adds support for the `-scheduler=tasks` flag for AVR. On most AVR chips you wouldn't want to run a real scheduler but it may be useful in some cases, especially on devices with more RAM. It is disabled by default.
89 lines
2.5 KiB
Go
89 lines
2.5 KiB
Go
// +build scheduler.tasks,avr
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package task
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import "unsafe"
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const stackSize = 256
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// calleeSavedRegs is the list of registers that must be saved and restored when
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// switching between tasks. Also see scheduler_avr.S that relies on the
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// exact layout of this struct.
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//
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// https://gcc.gnu.org/wiki/avr-gcc#Call-Saved_Registers
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type calleeSavedRegs struct {
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r2r3 uintptr
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r4r5 uintptr
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r6r7 uintptr
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r8r9 uintptr
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r10r11 uintptr
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r12r13 uintptr
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r14r15 uintptr
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r16r17 uintptr
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r28r29 uintptr // Y register
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pc uintptr
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}
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// registers gets a pointer to the registers stored at the top of the stack.
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func (s *state) registers() *calleeSavedRegs {
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return (*calleeSavedRegs)(unsafe.Pointer(s.sp + 1))
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}
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// startTask is a small wrapper function that sets up the first (and only)
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// argument to the new goroutine and makes sure it is exited when the goroutine
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// finishes.
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//go:extern tinygo_startTask
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var startTask [0]uint8
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// archInit runs architecture-specific setup for the goroutine startup.
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// Note: adding //go:noinline to work around an AVR backend bug.
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//go:noinline
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func (s *state) archInit(stack []uintptr, fn uintptr, args unsafe.Pointer) {
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// Set up the stack canary, a random number that should be checked when
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// switching from the task back to the scheduler. The stack canary pointer
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// points to the first word of the stack. If it has changed between now and
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// the next stack switch, there was a stack overflow.
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s.canaryPtr = &stack[0]
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*s.canaryPtr = stackCanary
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// Store the initial sp for the startTask function (implemented in assembly).
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s.sp = uintptr(unsafe.Pointer(&stack[uintptr(len(stack))-(unsafe.Sizeof(calleeSavedRegs{})/unsafe.Sizeof(uintptr(0)))])) - 1
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// Initialize the registers.
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// These will be popped off of the stack on the first resume of the goroutine.
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r := s.registers()
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// Start the function at tinygo_startTask.
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startTask := uintptr(unsafe.Pointer(&startTask))
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r.pc = startTask/2>>8 | startTask/2<<8
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// Pass the function to call in r2:r3.
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// This function is a compiler-generated wrapper which loads arguments out
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// of a struct pointer. See createGoroutineStartWrapper (defined in
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// compiler/goroutine.go) for more information.
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r.r2r3 = fn
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// Pass the pointer to the arguments struct in r4:45.
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r.r4r5 = uintptr(args)
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}
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func (s *state) resume() {
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switchToTask(s.sp)
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}
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//export tinygo_switchToTask
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func switchToTask(uintptr)
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//export tinygo_switchToScheduler
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func switchToScheduler(*uintptr)
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func (s *state) pause() {
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switchToScheduler(&s.sp)
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}
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//export tinygo_pause
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func pause() {
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Pause()
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}
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