path: root/ir.c

#include <stdarg.h>
#include "ir.h"

extern int no_opt;

const char *node_type_name(NodeType t) {
	const char *names[] = {
		"start",
		"return",
		"keepalive",
		"literal",
		"add", "sub", "mul", "div",
		"and", "or", "xor",
		"lshift", "rshift",
		"neg", "not",
		"value"
	};
	return names[t];
}

void node_die(Node *n, Proc *p) {
	n->prev_free = p->free_list;
	p->free_list = n;
}

void node_del_out(Node *n, Node *p) {
	for (int i = 0; i < n->out.len; i++) {
		if (n->out.data[i] == p) {
			p->refs--;
			if (i + 1 < n->out.len) {
				memmove(&n->out.data[i], &n->out.data[i + 1], sizeof(Node*) * (n->out.len - i - 1));
			}
			n->out.len--;
			i--;
		}
	}
}

void node_del_in(Node *n, Node *p) {
	for (int i = 0; i < n->in.len; i++) {
		if (n->in.data[i] == p) {
			p->refs--;
			if (i + 1 < n->in.len) {
				memmove(&n->in.data[i], &n->in.data[i + 1], sizeof(Node*) * (n->in.len - i - 1));
			}
			n->in.len--;
			i--;
		}
	}
}

void node_kill(Node *n, Proc *p) {
	for (int i = 0; i < n->in.len; i++) {
		node_del_out(n->in.data[i], n);
		n->in.data[i]->refs--;
		if (n->in.data[i]->out.len < 1) node_kill(n->in.data[i], p);
	}
	for (int i = 0; i < n->out.len; i++) {
		node_del_in(n->out.data[i], n);
		n->out.data[i]->refs--;
		if (n->out.data[i]->refs < 1) node_die(n->out.data[i], p);
	}
	n->in.len = 0;
	n->out.len = 0;
	node_die(n, p);
}

void node_add(Proc *p, Node *src, Node *dest) {
	ZDA_PUSH(&src->out, dest, &p->arena);
	ZDA_PUSH(&dest->in, src, &p->arena);
	src->refs++;
	dest->refs++;
	if (dest->src_pos.n == 0) dest->src_pos = src->src_pos;
}

void node_remove(Proc *p, Node *src, Node *dest) {
	node_del_out(src, dest);
	node_del_in(dest, src);
	if (dest->refs < 1) node_die(dest, p);
	if (src->refs < 1) node_die(src, p);
	else if (src->out.len < 1) node_kill(src, p);
}

static int global_node_count = 0;

Node *node_new_empty(Proc *p, NodeType t) {
	Node *n;
	if (p->free_list) {
		n = p->free_list;
		p->free_list = n->prev_free;
		memset(n, 0, sizeof(Node));
	} else {
		n = new(&p->arena, Node);
	}
	n->type = t;
	n->id = global_node_count++;
	return n;
}

Node *node_newv(Proc *p, NodeType t, ...) {
	Node *node = node_new_empty(p, t);
	va_list ap;
	va_start(ap, t);
	for (;;) {
		Node *n = va_arg(ap, Node *);
		if (!n) break;
		node_add(p, n, node);
	}
	va_end(ap);
	return node;
}

Node *node_dedup_lit(Proc *p, Value v) {
	/* TODO: this is probably real inefficient for large procedure graphs,
	 * but does it matter? how many nodes are direct children of the start node?
	 * how many literals even usually occur in a procedure? */
	for (int i = 0; i < p->start->out.len; i++) {
		Node *t = p->start->out.data[i];
		if (t->type == N_LIT && t->val.type == v.type && t->val.i == v.i) {
			return t;
		}
	}
	return NULL;
}

Node *node_new_lit_i64(Proc *p, int64_t i) {
	Value v = (Value) { T_INT, { .i = i } };
	Node *t = node_dedup_lit(p, v);
	if (t) return t;
	Node *n = node_new(p, N_LIT, p->start);
	n->val = v;
	return n;
}

static inline int node_op_communative(NodeType t) {
	NodeType ops[] = { N_OP_ADD, N_OP_MUL, N_OP_AND, N_OP_XOR, N_OP_OR };
	for (unsigned i = 0; i < sizeof ops / sizeof *ops; i++) {
		if (ops[i] == t) return 1;
	}
	return 0;
}

Value node_compute(Node *n, Lexer *l) {
	Type lit_type = T_BOT;
	Node **in = n->in.data;
	for (int i = 0; i < n->in.len; i++) {
		Node *p = in[i];
		if (p->type != N_LIT) break;
		if (p->val.type != lit_type) {
			if (lit_type == T_BOT) {
				lit_type = p->val.type;
			} else {
				lit_type = T_BOT;
				break;
			}
		}
	}
	if (lit_type == T_INT) {
		Value v = { .type = lit_type };
		switch (n->type) {
		case N_OP_NEG: v.i = -in[0]->val.i; break;
		case N_OP_NOT: v.i = ~in[0]->val.i; break;
		case N_OP_ADD: v.i = in[0]->val.i + in[1]->val.i; break;
		case N_OP_SUB: v.i = in[0]->val.i - in[1]->val.i; break;
		case N_OP_MUL: v.i = in[0]->val.i * in[1]->val.i; break;
		case N_OP_DIV:
			       if (in[1]->val.i == 0) {
				       lex_error_at(l, in[1]->src_pos, LE_ERROR, S("divisor always evaluates to zero"));
			       }
			       v.i = in[0]->val.i / in[1]->val.i;
			       break;
		case N_OP_AND: v.i = in[0]->val.i & in[1]->val.i; break;
		case N_OP_OR: v.i = in[0]->val.i | in[1]->val.i; break;
		case N_OP_XOR: v.i = in[0]->val.i ^ in[1]->val.i; break;
		case N_OP_SHL: v.i = in[0]->val.u << in[1]->val.u; break;
		case N_OP_SHR: v.i = in[0]->val.u >> in[1]->val.u; break;
		default: return n->val;
		}
		return v;
	}
	return n->val;
}

/* needs lexer for error reporting */
Node *node_peephole(Node *n, Proc *p, Lexer *l) {
	if (no_opt) return n;

	if (n->type != N_LIT) {
		Value v = node_compute(n, l);
		if (v.type > T_CONST) {
			node_kill(n, p);
			Node *t = node_dedup_lit(p, v);
			if (t) return t;
			Node *r = node_new(p, N_LIT, p->start);
			r->val = v;
			r->src_pos = n->src_pos;
			return r;
		}
	}

	Node **in = n->in.data;
	/* TODO: figure out to do peepholes recursively, without fucking up the graph or having to clone everything */
	if (node_op_communative(n->type)) {
		/* transformations to help encourage constant folding */
		/* the overall trend is to move them rightwards */
		if (in[0]->type == N_LIT
				&& in[1]->type == n->type
				&& in[1]->in.data[0]->type != N_LIT
				&& in[1]->in.data[1]->type == N_LIT) {
			/* op(lit, op(X, lit)) -> op(X, op(lit, lit)) */
			Node *tmp = in[1]->in.data[0];
			in[1]->in.data[0] = in[0];
			in[0] = tmp;
			/* TODO: ...would it break anything at all to just do in[1] = node_peephole(in[1], p, l)?
			 * probably not, right? */
		} else if (in[0]->type == n->type
				&& in[0]->in.data[0]->type != N_LIT
				&& in[0]->in.data[1]->type == N_LIT
				&& in[1]->type != N_LIT) {
			/* op(op(X, lit), Y) -> op(op(X, Y), lit) */
			Node *tmp = in[0]->in.data[1];
			in[0]->in.data[1] = in[1];
			in[1] = tmp;
		} else if (in[0]->type == N_LIT && in[1]->type != N_LIT) {
			/* op(lit, X) -> op(X, lit) */
			Node *tmp = in[0];
			in[0] = in[1];
			in[1] = tmp;
		}
	}

	return n;
}

/* procedures */

void proc_init(Proc *proc, Str name) {
	memset(proc, 0, sizeof(Proc));
	proc->start = node_new_empty(proc, N_START);
	proc->keepalive = node_new_empty(proc, N_KEEPALIVE);
	proc->name = name;
}

void proc_free(Proc *proc) {
	arena_free(&proc->arena);
}

/* scope */

NameBinding *scope_find(Scope *scope, Str name) {
	for (ScopeFrame *f = scope->tail; f; f = f->prev) {
		for (NameBinding *b = f->latest; b; b = b->prev) {
			if (str_eql(b->name, name)) {
				return b;
			}
		}
	}
	return NULL;
}

ScopeFrame *scope_push(Scope *scope, Proc *proc) {
	ScopeFrame *f;
	if (scope->free_scope) {
		f = scope->free_scope;
		*f = (ScopeFrame) { 0 };
		scope->free_scope = f->prev;
	} else {
		f = new(&proc->arena, ScopeFrame);
	}
	f->prev = scope->tail;
	scope->tail = f;
	return f;
}

ScopeFrame *scope_pop(Scope *scope, Proc *proc) {
	ScopeFrame *f = scope->tail;
	scope->tail = f->prev;
	f->prev = scope->free_scope;
	scope->free_scope = f;
	for (NameBinding *b = f->latest; b; ) {
		NameBinding *p = b->prev;
		b->prev = scope->free_bind;
		scope->free_bind = b;
		node_remove(proc, b->node, proc->keepalive);
		b = p;
	}
	return scope->tail;
}

/* returns previous value */
NameBinding *scope_bind(Scope *scope, Str name, Node *value, LexSpan pos, Proc *proc) {
	NameBinding *prev = scope_find(scope, name);
	NameBinding *b;
	if (scope->free_bind) {
		b = scope->free_bind;
		*b = (NameBinding) { 0 };
		scope->free_bind = b->prev;
	} else {
		b = new(&proc->arena, NameBinding);
	}
	b->name = name;
	b->prev = scope->tail->latest;
	scope->tail->latest = b;
	b->node = value;
	b->src_pos = pos;
	node_add(proc, value, proc->keepalive);
	return prev;
}