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/*
* a runtime implementation for
* https://github.com/llvm/llvm-project/pull/84137
* https://docs.google.com/document/d/1ZvTPT36K5jjiedF8MCXbEmYjULJjI723aOAks1IdLLg/edit
*/
#include <stddef.h>
#include <stdint.h>
/*
* function prototypes
*/
void __wasm_setjmp(void *env, uint32_t label, void *func_invocation_id);
uint32_t __wasm_setjmp_test(void *env, void *func_invocation_id);
void __wasm_longjmp(void *env, int val);
/*
* jmp_buf should have large enough size and alignment to contain
* this structure.
*/
struct jmp_buf_impl {
void *func_invocation_id;
uint32_t label;
/*
* this is a temorary storage used by the communication between
* __wasm_sjlj_longjmp and WebAssemblyLowerEmscriptenEHSjL-generated
* logic.
* ideally, this can be replaced with multivalue.
*/
struct arg {
void *env;
int val;
} arg;
};
void
__wasm_setjmp(void *env, uint32_t label, void *func_invocation_id)
{
struct jmp_buf_impl *jb = env;
if (label == 0) { /* ABI contract */
__builtin_trap();
}
if (func_invocation_id == NULL) { /* sanity check */
__builtin_trap();
}
jb->func_invocation_id = func_invocation_id;
jb->label = label;
}
uint32_t
__wasm_setjmp_test(void *env, void *func_invocation_id)
{
struct jmp_buf_impl *jb = env;
if (jb->label == 0) { /* ABI contract */
__builtin_trap();
}
if (func_invocation_id == NULL) { /* sanity check */
__builtin_trap();
}
if (jb->func_invocation_id == func_invocation_id) {
return jb->label;
}
return 0;
}
void
__wasm_longjmp(void *env, int val)
{
struct jmp_buf_impl *jb = env;
struct arg *arg = &jb->arg;
/*
* C standard says:
* The longjmp function cannot cause the setjmp macro to return
* the value 0; if val is 0, the setjmp macro returns the value 1.
*/
if (val == 0) {
val = 1;
}
arg->env = env;
arg->val = val;
__builtin_wasm_throw(1, arg); /* 1 == C_LONGJMP */
}
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