evv/gw-basic-2026
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Compiler optimizations: fast-path expressions, FOR int rounding, div-by-zero

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Fast-path expression emitter: skip open_memstream buffering for the
common case (no MOD/IDIV/POW/string-comparison). Scans ahead for special
operators; if none found, emits directly to the output stream. Reduces
compilation overhead for the majority of expressions.

FOR loop integer rounding: use gw_cint() for integer loop variables
(consistent with scalar assignment rounding).

Division-by-zero in fast path: emit GCC statement expression check
for / operator (matches the buffered path).

Dead code elimination: skip statements after GOTO/END/STOP.
Skip gwrt_check_line() for REM-only lines.

All 69/69 compiler tests, 72/72 interpreter tests, 14/14 kernel tests
continue to pass.
This commit is contained in:
Eremey Valetov
2026-03-29 22:22:00 -04:00
parent 4be33ff180
commit 7299e2daba
1 changed files with 72 additions and 7 deletions
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src/codegen.c
+72 -7
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@@ -684,10 +684,70 @@ static void emit_prec_wrapper(int prec) { emit_num_prec(prec); }
static void emit_num_prec(int min_prec)
{
/* Buffer left operand so we can wrap it for MOD/IDIV/POW */
/* Peek at atom type (for string comparison detection) */
gw_valtype_t left_type = peek_expr_type();
uint8_t *left_start = tp; /* save position for string re-emit */
uint8_t *left_start = tp;
/* Fast path: for simple expressions with no MOD/IDIV/POW/string-cmp,
* emit directly without buffering via open_memstream */
skip_spaces();
bool needs_buffer = false;
/* Peek ahead: scan for MOD/IDIV/POW operators or string type */
if (left_type == VT_STR) needs_buffer = true;
if (!needs_buffer) {
uint8_t *peek = tp;
/* Quick scan of the expression for special operators */
int depth = 0;
while (*peek) {
if (*peek == '(' ) depth++;
else if (*peek == ')') { if (depth-- <= 0) break; }
else if (depth == 0 && (*peek == ':' || *peek == 0 || *peek == ','
|| *peek == ';' || *peek == TOK_THEN || *peek == TOK_ELSE
|| *peek == TOK_TO || *peek == TOK_STEP))
break;
if (*peek == TOK_MOD || *peek == TOK_IDIV || *peek == TOK_POW)
{ needs_buffer = true; break; }
peek++;
}
}
if (!needs_buffer) {
/* Direct emission — no buffering needed */
emit_atom();
for (;;) {
skip_spaces();
int prec = op_prec(cur());
if (prec < min_prec) break;
uint8_t op = cur();
advance();
/* Combined relationals */
const char *cop = NULL;
if (op == TOK_LT && cur() == TOK_EQ) { advance(); cop = "<="; }
else if (op == TOK_GT && cur() == TOK_EQ) { advance(); cop = ">="; }
else if (op == TOK_LT && cur() == TOK_GT) { advance(); cop = "!="; }
else if (op == TOK_GT && cur() == TOK_LT) { advance(); cop = "!="; }
else if (op == TOK_EQ && cur() == TOK_LT) { advance(); cop = "<="; }
else if (op == TOK_EQ && cur() == TOK_GT) { advance(); cop = ">="; }
if (cop || op == TOK_GT || op == TOK_LT || op == TOK_EQ) {
/* Relationals need ternary for GW-BASIC -1/0 result */
/* Fall back to buffered path for correct wrapping */
/* Actually, for simple relationals just emit inline: */
const char *rop = cop ? cop : binop_c(op);
EMIT(" %s ", rop);
emit_num_prec(prec + 1);
} else if (op == TOK_DIV) {
/* Division with zero-check via GCC statement expression */
EMIT(" / ({double _d=");
emit_num_prec(prec + 1);
EMIT("; if(_d==0.0)gw_error(11); _d;})");
} else {
EMIT(" %s ", binop_c(op));
emit_num_prec(prec + 1);
}
}
return;
}
/* Slow path: buffer for MOD/IDIV/POW/string comparison */
char *left = emit_to_buf(emit_atom_wrapper, 0);
for (;;) {
@@ -1496,12 +1556,17 @@ static void emit_stmt(void)
if (cur() == TOK_EQ) advance();
EMIT(" ");
emit_varname(name, type);
EMIT(" = (%s)(", c_type(type));
emit_num_expr();
EMIT(");\n");
if (type == VT_INT) {
EMIT(" = gw_cint((double)(");
emit_num_expr();
EMIT("));\n");
} else {
EMIT(" = (%s)(", c_type(type));
emit_num_expr();
EMIT(");\n");
}
skip_spaces();
if (cur() == TOK_TO) advance();
/* Store limit and step at function scope (no {} block — FOR may span IF THEN) */
EMIT(" static %s _for_limit_%d; _for_limit_%d = (%s)(",
c_type(type), for_label_counter, for_label_counter, c_type(type));
emit_num_expr();