source: libcfa/src/concurrency/CtxSwitch-x86_64.S@ dbae916

//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// CtxSwitch-x86_64.S --
//
// Author           : Peter A. Buhr
// Created On       : Mon Aug 10 08:10:26 2020
// Last Modified By : Peter A. Buhr
// Last Modified On : Sat Oct 24 14:36:25 2020
// Update Count     : 10
//

// The context switch routine requires the initial the stack of a thread to
// look like the thread has saved its context in the normal manner.

// Offsets must synchronized with the __stack_context_t in invoke.h.

#define PTR_BYTE        8
#define SP_OFFSET       ( 0 * PTR_BYTE )
#define FP_OFFSET       ( 1 * PTR_BYTE )

// Context switch between coroutines/tasks.
//   void __cfactx_switch( struct __stack_context_t * from, struct __stack_context_t * to ) ;
// Arguments "from" in register rdi, "to" in register rsi.

        .file "CtxSwitch-x86_64.S"
        .text
        .align 2
        .global __cfactx_switch
        .type __cfactx_switch, @function
__cfactx_switch:

        // Save volatile registers on the stack.

        pushq %r15
        pushq %r14
        pushq %r13
        pushq %r12
        pushq %rbx

        // Save old context in the "from" area.

        movq %rsp,SP_OFFSET(%rdi)
        movq %rbp,FP_OFFSET(%rdi)

        // Load new context from the "to" area.

        movq SP_OFFSET(%rsi),%rsp
        movq FP_OFFSET(%rsi),%rbp

        // Load volatile registers from the stack.

        popq %rbx
        popq %r12
        popq %r13
        popq %r14
        popq %r15

        // Return to thread.

        ret
        .size __cfactx_switch, .-__cfactx_switch

// Stub to create new stacks which can be context switched to
//   void __cfactx_invoke_stub( void );

        .text
        .align 2
        .global __cfactx_invoke_stub
        .type __cfactx_invoke_stub, @function
__cfactx_invoke_stub:
        movq %rbx, %rdi                                         // move main and this to first two arguments
        movq %r12, %rsi
        jmp *%r13                                                       // jmp to invoke
        .size __cfactx_invoke_stub, .-__cfactx_invoke_stub

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