bsnes/libco/ucontext.c
Tim Allen c6fc15f8d2 Update to v101r18 release.
byuu says:

Changelog:

  - added 30 new PAL games to icarus (courtesy of Mikerochip)
  - new version of libco no longer requires mprotect nor W|X permissions
  - nall: default C compiler to -std=c11 instead of -std=c99
  - nall: use `-fno-strict-aliasing` during compilation
  - updated nall/certificates (hopefully for the last time)
  - updated nall/http to newer coding conventions
  - nall: improve handling of range() function

I didn't really work on higan at all, this is mostly just a release
because lots of other things have changed.

The most interesting is `-fno-strict-aliasing` ... basically, it joins
`-fwrapv` as being "stop the GCC developers from doing *really* evil
shit that could lead to security vulnerabilities or instabilities."

For the most part, it's a ~2% speed penalty for higan. Except for the
Sega Genesis, where it's a ~10% speedup. I have no idea how that's
possible, but clearly something's going very wrong with strict aliasing
on the Genesis core.

So ... it is what it is. If you need the performance for the non-Genesis
cores, you can turn it off in your builds. But I'm getting quite sick of
C++'s "surprises" and clever compiler developers, so I'm keeping it on
in all of my software going forward.
2016-09-14 21:55:53 +10:00

70 lines
1.7 KiB
C

/*
libco.ucontext (2008-01-28)
author: Nach
license: public domain
*/
/*
WARNING: the overhead of POSIX ucontext is very high,
assembly versions of libco or libco_sjlj should be much faster
this library only exists for two reasons:
1: as an initial test for the viability of a ucontext implementation
2: to demonstrate the power and speed of libco over existing implementations,
such as pth (which defaults to wrapping ucontext on unix targets)
use this library only as a *last resort*
*/
#define LIBCO_C
#include "libco.h"
#define _BSD_SOURCE
#include <stdlib.h>
#include <ucontext.h>
#ifdef __cplusplus
extern "C" {
#endif
static thread_local ucontext_t co_primary;
static thread_local ucontext_t* co_running = 0;
cothread_t co_active() {
if(!co_running) co_running = &co_primary;
return (cothread_t)co_running;
}
cothread_t co_create(unsigned int heapsize, void (*coentry)(void)) {
if(!co_running) co_running = &co_primary;
ucontext_t* thread = (ucontext_t*)malloc(sizeof(ucontext_t));
if(thread) {
if((!getcontext(thread) && !(thread->uc_stack.ss_sp = 0)) && (thread->uc_stack.ss_sp = malloc(heapsize))) {
thread->uc_link = co_running;
thread->uc_stack.ss_size = heapsize;
makecontext(thread, coentry, 0);
} else {
co_delete((cothread_t)thread);
thread = 0;
}
}
return (cothread_t)thread;
}
void co_delete(cothread_t cothread) {
if(cothread) {
if(((ucontext_t*)cothread)->uc_stack.ss_sp) { free(((ucontext_t*)cothread)->uc_stack.ss_sp); }
free(cothread);
}
}
void co_switch(cothread_t cothread) {
ucontext_t* old_thread = co_running;
co_running = (ucontext_t*)cothread;
swapcontext(old_thread, co_running);
}
#ifdef __cplusplus
}
#endif