Implementation of Unlambda, an esoteric programming language.
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/*
* vm_stack.c - Unlambda VM segmented stacks
*
* Copyright (C) 2020 CismonX <admin@cismon.net>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "vm_stack.h"
#include "vm_pool.h"
#include "logging.h"
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
struct vm_stack {
struct vm_stack* prev;
uint32_t top;
uint32_t refcnt;
struct u6a_vm_var_fn elems[];
};
static struct vm_stack* active_stack;
static uint32_t stack_seg_len;
const char* err_stage;
static inline struct vm_stack*
vm_stack_create(struct vm_stack* prev, uint32_t top) {
const uint32_t size = sizeof(struct vm_stack) + stack_seg_len * sizeof(struct u6a_vm_var_fn);
struct vm_stack* vs = malloc(size);
if (UNLIKELY(vs == NULL)) {
u6a_err_bad_alloc(err_stage, size);
return NULL;
}
vs->prev = prev;
vs->top = top;
vs->refcnt = 1;
return vs;
}
static inline struct vm_stack*
vm_stack_dup(struct vm_stack* vs) {
const uint32_t size = sizeof(struct vm_stack) + stack_seg_len * sizeof(struct u6a_vm_var_fn);
struct vm_stack* dup_stack = malloc(size);
if (UNLIKELY(dup_stack == NULL)) {
u6a_err_bad_alloc(err_stage, size);
return NULL;
}
memcpy(dup_stack, vs, sizeof(struct vm_stack) + (vs->top + 1) * sizeof(struct u6a_vm_var_fn));
dup_stack->refcnt = 1;
for (uint32_t idx = vs->top; idx < UINT32_MAX; --idx) {
struct u6a_vm_var_fn elem = vs->elems[idx];
if (elem.token.fn & U6A_VM_FN_REF) {
u6a_vm_pool_addref(elem.ref);
}
}
if (vs->prev) {
++vs->prev->refcnt;
}
return dup_stack;
}
static inline void
vm_stack_free(struct vm_stack* vs) {
struct vm_stack* prev;
do {
prev = vs->prev;
if (--vs->refcnt == 0) {
for (uint32_t idx = vs->top; idx < UINT32_MAX; --idx) {
struct u6a_vm_var_fn elem = vs->elems[idx];
if (elem.token.fn & U6A_VM_FN_REF) {
u6a_vm_pool_free(elem.ref);
}
}
free(vs);
vs = prev;
} else {
break;
}
} while (vs);
}
bool
u6a_vm_stack_init(uint32_t stack_seg_len_, const char* err_stage_) {
stack_seg_len = stack_seg_len_;
err_stage = err_stage_;
active_stack = vm_stack_create(NULL, UINT32_MAX);
return active_stack != NULL;
}
U6A_HOT struct u6a_vm_var_fn
u6a_vm_stack_top() {
struct vm_stack* vs = active_stack;
if (UNLIKELY(vs->top == UINT32_MAX)) {
vs = vs->prev;
if (UNLIKELY(vs == NULL)) {
return (struct u6a_vm_var_fn) { 0 };
}
active_stack = vs;
}
return vs->elems[vs->top];
}
// Boilerplates below. If only we have C++ templates here... (macros just make things nastier)
U6A_HOT bool
u6a_vm_stack_push1(struct u6a_vm_var_fn v0) {
struct vm_stack* vs = active_stack;
if (LIKELY(vs->top + 1 < stack_seg_len)) {
vs->elems[++vs->top] = v0;
return true;
}
active_stack = vm_stack_create(vs, 0);
if (UNLIKELY(active_stack == NULL)) {
active_stack = vs;
return false;
}
++vs->refcnt;
active_stack->elems[0] = v0;
return true;
}
U6A_HOT bool
u6a_vm_stack_push2(struct u6a_vm_var_fn v0, struct u6a_vm_var_fn v1) {
struct vm_stack* vs = active_stack;
if (LIKELY(vs->top + 2 < stack_seg_len)) {
vs->elems[++vs->top] = v0;
vs->elems[++vs->top] = v1;
return true;
}
active_stack = vm_stack_create(vs, 1);
if (UNLIKELY(active_stack == NULL)) {
active_stack = vs;
return false;
}
++vs->refcnt;
active_stack->elems[0] = v0;
active_stack->elems[1] = v1;
return true;
}
U6A_HOT bool
u6a_vm_stack_push3(struct u6a_vm_var_fn v0, struct u6a_vm_var_tuple v12) {
struct vm_stack* vs = active_stack;
if (LIKELY(vs->top + 3 < stack_seg_len)) {
vs->elems[++vs->top] = v0;
vs->elems[++vs->top] = v12.v2.fn;
vs->elems[++vs->top] = v12.v1.fn;
return true;
}
active_stack = vm_stack_create(vs, 2);
if (UNLIKELY(active_stack == NULL)) {
active_stack = vs;
return false;
}
++vs->refcnt;
active_stack->elems[0] = v0;
active_stack->elems[1] = v12.v2.fn;
active_stack->elems[2] = v12.v1.fn;
return true;
}
U6A_HOT bool
u6a_vm_stack_push4(struct u6a_vm_var_fn v0, struct u6a_vm_var_fn v1, struct u6a_vm_var_tuple v23) {
struct vm_stack* vs = active_stack;
if (LIKELY(vs->top + 4 < stack_seg_len)) {
vs->elems[++vs->top] = v0;
vs->elems[++vs->top] = v1;
vs->elems[++vs->top] = v23.v2.fn;
vs->elems[++vs->top] = v23.v1.fn;
return true;
}
active_stack = vm_stack_create(vs, 3);
if (UNLIKELY(active_stack == NULL)) {
active_stack = vs;
return false;
}
++vs->refcnt;
active_stack->elems[0] = v0;
active_stack->elems[1] = v1;
active_stack->elems[2] = v23.v2.fn;
active_stack->elems[3] = v23.v1.fn;
return true;
}
U6A_HOT bool
u6a_vm_stack_pop() {
struct vm_stack* vs = active_stack;
if (LIKELY(vs->top-- < UINT32_MAX)) {
return true;
}
active_stack = vs->prev;
if (UNLIKELY(active_stack == NULL)) {
u6a_err_stack_underflow(err_stage);
active_stack = vs;
return false;
}
if (--active_stack->refcnt > 0) {
active_stack = vm_stack_dup(active_stack);
}
if (UNLIKELY(active_stack == NULL)) {
active_stack = vs;
return false;
};
free(vs);
--active_stack->top;
return true;
}
struct u6a_vm_var_fn
u6a_vm_stack_xch(struct u6a_vm_var_fn v0) {
struct vm_stack* vs = active_stack;
struct u6a_vm_var_fn elem = vs->elems[vs->top - 1];
vs->elems[vs->top - 1] = v0;
return elem;
}
void*
u6a_vm_stack_save() {
return vm_stack_dup(active_stack);
}
void*
u6a_vm_stack_dup(void* ptr) {
return vm_stack_dup(ptr);
}
void
u6a_vm_stack_resume(void* ptr) {
u6a_vm_stack_destroy();
active_stack = ptr;
}
void
u6a_vm_stack_discard(void* ptr) {
vm_stack_free(ptr);
}
void
u6a_vm_stack_destroy() {
vm_stack_free(active_stack);
}