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nicolasnoblenicolasnoble
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Merge pull request #1934 from nicolasnoble/ucontext
Adding ucontext.
2 parents 7730d21 + 9afc64a commit 0c18816

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‎src/mips/common/psxlibc/ucontext.h‎

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/*
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MIT License
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Copyright (c) 2025 PCSX-Redux authors
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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#pragma once
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// This file provides an ersatz for the ucontext.h API, which is otherwise not available on PSX.
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// It defines the necessary structures and function prototypes to allow for context switching,
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// similar to what ucontext.h provides in POSIX systems. It's not strictly compliant with the POSIX standard,
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// but it provides a minimal implementation suitable for coroutine management in a PSX environment.
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#include <stdint.h>
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struct stack_t {
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void *ss_sp;
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unsigned ss_size;
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};
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struct mcontext_t {
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uint32_t reserved[16];
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};
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struct ucontext_t {
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struct mcontext_t uc_mcontext;
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struct ucontext_t *uc_link;
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struct stack_t uc_stack;
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};
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#ifdef __cplusplus
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extern "C" {
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#endif
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int getcontext(struct ucontext_t *ucp);
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int setcontext(const struct ucontext_t *ucp);
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int makecontext(struct ucontext_t *ucp, void (*func)(void *), void *arg);
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int swapcontext(struct ucontext_t *oucp, const struct ucontext_t *ucp);
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#ifdef __cplusplus
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}
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#endif

‎src/mips/common/psxlibc/ucontext.s‎

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/*
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MIT License
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Copyright (c) 2025 PCSX-Redux authors
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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.set RAPTR, 0
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.set SPPTR, 4
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.set S8PTR, 8
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.set S0PTR, 12
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.set S1PTR, 16
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.set S2PTR, 20
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.set S3PTR, 24
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.set S4PTR, 28
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.set S5PTR, 32
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.set S6PTR, 36
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.set S7PTR, 40
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.set GPPTR, 44
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.set FUNCPTR, 48
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.set ARGPTR, 52
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.set UNUSED1, 56
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.set UNUSED2, 60
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.set LINKPTR, 64
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.set STACKPTR, 68
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.set STACKSIZE, 72
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.section .text.getcontext, "ax", @progbits
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.align 2
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.global getcontext
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.type getcontext, @function
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getcontext:
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sw $ra, RAPTR($a0)
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sw $sp, SPPTR($a0)
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sw $s8, S8PTR($a0)
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sw $s0, S0PTR($a0)
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sw $s1, S1PTR($a0)
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sw $s2, S2PTR($a0)
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sw $s3, S3PTR($a0)
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sw $s4, S4PTR($a0)
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sw $s5, S5PTR($a0)
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sw $s6, S6PTR($a0)
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sw $s7, S7PTR($a0)
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sw $gp, GPPTR($a0)
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move $v0, $0
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jr $ra
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.section .text.setcontext, "ax", @progbits
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.align 2
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.global setcontext
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.type setcontext, @function
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setcontext:
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lw $ra, RAPTR($a0)
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lw $sp, SPPTR($a0)
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lw $s8, S8PTR($a0)
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lw $s0, S0PTR($a0)
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lw $s1, S1PTR($a0)
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lw $s2, S2PTR($a0)
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lw $s3, S3PTR($a0)
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lw $s4, S4PTR($a0)
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lw $s5, S5PTR($a0)
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lw $s6, S6PTR($a0)
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lw $s7, S7PTR($a0)
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lw $gp, GPPTR($a0)
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move $v0, $0
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jr $ra
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.section .text.makecontext, "ax", @progbits
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.align 2
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.global makecontext
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.type makecontext, @function
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.type contexttrampoline, @function
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contexttrampoline:
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lw $a0, ARGPTR($s0)
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lw $a1, FUNCPTR($s0)
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lw $sp, SPPTR($s0)
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lw $s8, S8PTR($s0)
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lw $gp, GPPTR($s0)
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jalr $a1
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lw $a0, LINKPTR($s0)
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j setcontext
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makecontext:
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lw $v1, STACKPTR($a0)
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lw $t0, STACKSIZE($a0)
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la $v0, contexttrampoline
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sw $v0, RAPTR($a0)
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sw $a1, FUNCPTR($a0)
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sw $a2, ARGPTR($a0)
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sw $a0, S0PTR($a0)
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addu $v1, $t0
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sw $v1, SPPTR($a0)
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jr $ra
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.section .text.swapcontext, "ax", @progbits
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.align 2
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.global swapcontext
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.type swapcontext, @function
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swapcontext:
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sw $ra, RAPTR($a0)
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sw $sp, SPPTR($a0)
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sw $s8, S8PTR($a0)
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sw $s0, S0PTR($a0)
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sw $s1, S1PTR($a0)
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sw $s2, S2PTR($a0)
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sw $s3, S3PTR($a0)
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sw $s4, S4PTR($a0)
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sw $s5, S5PTR($a0)
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sw $s6, S6PTR($a0)
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sw $s7, S7PTR($a0)
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sw $gp, GPPTR($a0)
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lw $ra, RAPTR($a1)
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lw $sp, SPPTR($a1)
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lw $s8, S8PTR($a1)
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lw $s0, S0PTR($a1)
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lw $s1, S1PTR($a1)
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lw $s2, S2PTR($a1)
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lw $s3, S3PTR($a1)
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lw $s4, S4PTR($a1)
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lw $s5, S5PTR($a1)
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lw $s6, S6PTR($a1)
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lw $s7, S7PTR($a1)
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lw $gp, GPPTR($a1)
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move $v0, $0
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jr $ra

‎src/mips/psyqo/Makefile‎

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../common/crt0/memory-c.c \
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../common/crt0/memory-s.s \
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../common/hardware/flushcache.s \
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../common/psxlibc/ucontext.s \
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../common/syscalls/printf.s \
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$(wildcard src/hardware/*.cpp) \
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$(wildcard src/*.cpp) \

‎src/mips/psyqo/coroutine.hh‎

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#pragma once
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#include <EASTL/functional.h>
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#include <EASTL/utility.h>
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#include <coroutine>
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#include <type_traits>
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#include "common/psxlibc/ucontext.h"
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#include "common/syscalls/syscalls.h"
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namespace psyqo {
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}
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};
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class StackfulBase {
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protected:
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void initializeInternal(eastl::function<void()>&& func, void* ss_sp, unsigned ss_size);
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void resume();
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void yield();
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[[nodiscard]] bool isAlive() const { return m_isAlive; }
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StackfulBase() = default;
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StackfulBase(const StackfulBase&) = delete;
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StackfulBase& operator=(const StackfulBase&) = delete;
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private:
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static void trampoline(void* arg) {
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StackfulBase* self = static_cast<StackfulBase*>(arg);
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self->trampoline();
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}
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void trampoline();
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ucontext_t m_coroutine;
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ucontext_t m_return;
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eastl::function<void()> m_func;
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bool m_isAlive = false;
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};
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/**
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* @brief Stackful coroutine class.
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*
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* @details This class provides a simple stackful coroutine implementation.
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* It allows you to create coroutines that can yield and resume execution.
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* While the Coroutine class above is a C++20 coroutine, it requires
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* that all of the code being run are coroutines or awaitables all the way down.
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* This class is a more traditional coroutine implementation that uses
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* a separate stack for each coroutine, allowing it to yield and resume
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* execution without requiring the entire call stack to be coroutine-aware.
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* It is suitable for use in scenarios where you need to yield execution
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* from legacy code without converting it to C++20 coroutines.
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*/
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template <unsigned StackSize = 0x10000>
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class Stackful : public StackfulBase {
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public:
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static constexpr unsigned c_stackSize = (StackSize + 7) & ~7;
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Stackful() = default;
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Stackful(const Stackful&) = delete;
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Stackful& operator=(const Stackful&) = delete;
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/**
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* @brief Initialize the coroutine with a function and an argument.
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*
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* @param func Function to be executed by the coroutine.
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* @param arg Argument to be passed to the function.
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*/
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void initialize(eastl::function<void()>&& func) {
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initializeInternal(eastl::move(func), m_stack.data, c_stackSize);
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}
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/**
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* @brief Resume the coroutine.
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*
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* @details This will switch to the coroutine's context and execute it.
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* If the coroutine is not alive, this function does nothing. This
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* function should be called after the coroutine has been initialized,
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* and it will return to the point where the coroutine was last yielded.
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* It can only be called from the "main thread".
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*/
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void resume() { StackfulBase::resume(); }
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/**
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* @brief Yield the coroutine.
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*
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* @details This will switch back to the main thread and save the
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* coroutine's context. The coroutine can be resumed later using
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* `resume()`. It can only be called from within the coroutine
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* to yield execution.
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*/
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void yield() { StackfulBase::yield(); }
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/**
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* @brief Check if the coroutine is currently alive.
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* @details A coroutine is considered alive if it has been initialized
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* and has not yet completed its execution. It becomes not alive
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* when it returns from its function.
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*
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* @return true if the coroutine is alive, false otherwise.
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*/
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[[nodiscard]] bool isAlive() const { return StackfulBase::isAlive(); }
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private:
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struct alignas(8) Stack {
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uint8_t data[c_stackSize];
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};
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Stack m_stack;
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};
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} // namespace psyqo

‎src/mips/psyqo/examples/coroutine-demo-3/Makefile‎

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TARGET = coroutine-demo-3
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TYPE = ps-exe
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SRCS = \
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coroutine-demo-3.cpp \
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ifeq ($(TEST),true)
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CPPFLAGS = -Werror
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endif
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CXXFLAGS = -std=c++20 -fcoroutines
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include ../../psyqo.mk

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