context 3.0.0

Cooperative multitasking for Rust using Boost.Context
Documentation 
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	.globl	make_fcontext[DS]
	.globl .make_fcontext[PR]
	.align 2 
	.csect .make_fcontext[PR], 3
	.globl _make_fcontext
#._make_fcontext:
    # save return address into R6
    mflr  6

    # first arg of make_fcontext() == top address of context-function
    # shift address in R3 to lower 16 byte boundary
    clrrwi  3, 3, 4

    # reserve space for context-data on context-stack
    # including 64 byte of linkage + parameter area (R1 % 16 == 0)
    subi  3, 3, 248

    # third arg of make_fcontext() == address of context-function
    stw  5, 176(3)

    # set back-chain to zero
    li   0, 0
    std  0, 184(3)

    # compute address of returned transfer_t
    addi 0, 3, 232
    mr   4, 0
    std  4, 152(3)

    # load LR
    mflr  0
    # jump to label 1
    bl  .Label
.Label:
    # load LR into R4
    mflr  4
    # compute abs address of label .L_finish
    addi  4, 4, .L_finish - .Label
    # restore LR
    mtlr  0
    # save address of finish as return-address for context-function
    # will be entered after context-function returns
    stw  4, 168(3)

    # restore return address from R6
    mtlr  6

    blr  # return pointer to context-data

.L_finish:
    # save return address into R0
    mflr  0
    # save return address on stack, set up stack frame
    stw  0, 8(1)
    # allocate stack space, R1 % 16 == 0
    stwu  1, -32(1)

    # exit code is zero
    li  3, 0
    # exit application
    bl  ._exit
    nop