task_stack_mipsx.S

// Do not reorder instructions to insert a branch delay slot.
// We know what we're doing, and will manually fill the branch delay slot.
.set noreorder

.section .text.tinygo_startTask
.global  tinygo_startTask
.type    tinygo_startTask, %function
tinygo_startTask:
    // Small assembly stub for starting a goroutine. This is already run on the
    // new stack, with the callee-saved registers already loaded.
    // Most importantly, s0 contains the pc of the to-be-started function and s1
    // contains the only argument it is given. Multiple arguments are packed
    // into one by storing them in a new allocation.

    // Set the first argument of the goroutine start wrapper, which contains all
    // the arguments.
    move  $a0, $s1

    // Branch to the "goroutine start" function. Use jalr to write the return
    // address to ra so we'll return here after the goroutine exits.
    jalr  $s0
    nop

    // After return, exit this goroutine. This is a tail call.
    j     tinygo_task_exit
    nop

.section .text.tinygo_swapTask
.global  tinygo_swapTask
.type    tinygo_swapTask, %function
tinygo_swapTask:
    // This function gets the following parameters:
    //   a0 = newStack uintptr
    //   a1 = oldStack *uintptr

    // Push all callee-saved registers.
    addiu $sp, $sp, -40
    sw $ra, 36($sp)
    sw $s8, 32($sp)
    sw $s7, 28($sp)
    sw $s6, 24($sp)
    sw $s5, 20($sp)
    sw $s4, 16($sp)
    sw $s3, 12($sp)
    sw $s2,  8($sp)
    sw $s1,  4($sp)
    sw $s0,   ($sp)

    // Save the current stack pointer in oldStack.
    sw $sp, 0($a1)

    // Switch to the new stack pointer.
    move $sp, $a0

    // Pop all saved registers from this new stack.
    lw $ra,  36($sp)
    lw $s8,  32($sp)
    lw $s7,  28($sp)
    lw $s6,  24($sp)
    lw $s5,  20($sp)
    lw $s4,  16($sp)
    lw $s3,  12($sp)
    lw $s2,   8($sp)
    lw $s1,   4($sp)
    lw $s0,    ($sp)
    addiu $sp, $sp, 40

    // Return into the task.
    jalr $ra
    nop