merge work/known-bugs: constant-expression precedence, local const in constant expressions, duplicate case labels, unterminated strings, droppable cycles in one collection, js vm exit, docs, actors_demo orderHEADmain

1 files changed, 54 insertions, 14 deletions

diff --git a/src/compiler/expr.zc b/src/compiler/expr.zc
index 2935a9b..e437d2f 100644
--- a/src/compiler/expr.zc
+++ b/src/compiler/expr.zc
@@ -1072,6 +1072,7 @@ int primary() {
 		if (isfl(ltype[i])) xfloat = 1;
 		xstr = getstr(i); if (xty == tbstr) xstr = 1;
 		lv = 1; lvk = LV_LOCAL; lvi = i;
+		if ((ltag[i] & LCONST) && treadonly(xty)) { xconst = 1; xcval = lkval[i]; }	// a local const's value is known (spec 3.14.2)
 		if (isalias(i)) { touch(i); xbor = lroot(i); return C_VAR + i; }
 		if (tracked(i) || lrskind[i] == RS_PARAM || (local_origin_mask && local_origin_mask[i])) return C_VAR + i;
 		return C_PLAIN;
@@ -1762,17 +1763,31 @@ int unary() {
 // level tighter and emit its code sequence from the operator table. && and ||
 // short-circuit with jumps; floats get their own opcodes; a * or / by a
 // constant that is a power of two gets a shift hint in check mode.
+// fold a binary operator on two known integers; *ok is set to 0 when it can't be folded
+int cfold(int o, int a, int b, word ok) {
+	if (o == bname[0]) return a * b;
+	if (o == bname[1] || o == bname[2]) { if (b == 0) { ok[0] = 0; return 0; } if (o == bname[1]) return a / b; return a % b; }
+	if (o == bname[3]) return a + b;
+	if (o == bname[4]) return a - b;
+	if (o == bname[5]) return a << b;
+	if (o == bname[6]) return a >> b;
+	if (o == bname[13]) return a & b;
+	if (o == bname[14]) return a ^ b;
+	if (o == bname[15]) return a | b;
+	ok[0] = 0; return 0;
+}
 int if_comparison(int name) {
 	return name == s_eqeq || name == s_ne || name == s_lt || name == s_gt || name == s_le || name == s_ge;
 }
 int bin(int minp) {
-	int c = unary(), b, p, a, j, lt, lb, rb, src, lf, rf, ls, rs, fresh, top = 0, il = -1, opp, lu, ru, xu; word borrowed, rightborrow, left_mask, right_mask, infer_left, infer_right;
+	int lk = 0, lkv = 0, c = unary(), b, p, a, j, lt, lb, rb, src, lf, rf, ls, rs, fresh, top = 0, il = -1, opp, lu, ru, xu; word borrowed, rightborrow, left_mask, right_mask, infer_left, infer_right;
 	if (fortest == 1) { fortest = 2; top = 1; ft_nops = 0; }
 	while (tk == T_OP) {
 		b = binfind(tv);
 		if (b < 0) return c;
 		p = bprec[b];
 		if (p < minp) return c;
+		lk = 0;
 		lb = -1;
 		if (c >= C_VAR && tracked(c - C_VAR)) lb = lroot(c - C_VAR); else lb = xbor;
 		borrowed = xaf; left_mask = effect_mask(c); lf = xfloat; ls = xstr; fresh = 0;
@@ -1807,6 +1822,7 @@ int bin(int minp) {
 			setlit(j, here);
 			xfloat = 0; xstr = 0;
 		} else {
+			lk = xconst && !lf && !ls; lkv = xcval;
 			c = bin(p + 1); infer_right = if_value; rightborrow = xaf; right_mask = effect_mask(c);
 			rb = -1;
 			if (c >= C_VAR && tracked(c - C_VAR)) rb = lroot(c - C_VAR); else rb = xbor;
@@ -1818,6 +1834,7 @@ int bin(int minp) {
 				shifthint(opp, xcval);
 			}
 			rf = xfloat; rs = xstr;
+			if (lk && xconst && !rf && !rs && !isfl(xty)) { lk = 2; lkv = cfold(bname[b], lkv, xcval, &lk); }
 			if (isfl(xty)) rf = 1;
 			if ((ls || rs) && (bname[b] == s_plus || bname[b] == s_eqeq || bname[b] == s_ne || bname[b] == s_lt || bname[b] == s_gt || bname[b] == s_le || bname[b] == s_ge)) {
 				if (!(ls && rs)) serr("a byte string needs a byte string on the other side");
@@ -1856,6 +1873,7 @@ int bin(int minp) {
 		if (xu > 0x40000000) xu = 0 - 1;
 		xub = xu; xubat = here;
 		lv = 0; lvk = LV_NONE; c = C_PLAIN; xzero = 0; xconst = 0; xlenloc = -1; xstamp = 0; xaf = 0; xvk = 0;
+		if (lk == 2 && blen[b] > 0) { xconst = 1; xcval = lkv; }	// both sides constant: the value is known
 		effect_value = 0; if (isptr(xty) || xty == tword) effect_value = left_mask | right_mask;
 		if (fresh) c = C_FRESH;
   if (borrowed && borrowed[2] == 5 && (isptr(xty) || xty == tword) && (bname[b] == s_plus || bname[b] == s_minus)) xaf = borrowed;
@@ -2032,7 +2050,7 @@ int blockexpr() {
 
 // constant expressions, evaluated while compiling: numbers, named constants,
 // addresses of globals and functions, unary minus and ~, parentheses, and the
-// operators + - * | & << >>. used for array lengths, enum values, const
+// operators * / % + - << >> & ^ | at c precedence. used for array lengths, enum values, const
 // initializers and asm operands.
 word cprim() {
 	int v, s, mc;
@@ -2040,6 +2058,10 @@ word cprim() {
 	if (accept(s_minus)) return 0 - cprim();
 	if (tk == T_OP && tv == uname[2]) { next(); return ~cprim(); }
 	if (accept(s_lp)) { v = cexpr(); expect(s_rp); return v; }
+	if (tk == T_ID && nloc > 0) {	// a local const with a constant initializer (spec 3.14.2)
+		s = findloc(tv);
+		if (s >= 0 && (ltag[s] & LCONST) && !larr[s] && ltype[s] && treadonly(ltype[s])) { next(); return lkval[s]; }
+	}
 	if (tk == T_ID) {
 		s = lookup(tv);
 		if (mstruct && !ginst) { mc = lookup(methname(mstruct, tv)); if (mc >= 0 && skind[mc] == K_CONST) s = mc; }
@@ -2065,20 +2087,38 @@ word cprim() {
 	die("expected a constant");
 	return 0;
 }
-// compile an expression: a primary, then the operators that follow it.
-int cexpr() {
-	int v = cprim(), o;
+// a constant expression with c precedence: * / % above + -, above << >>,
+// above &, above ^, above | (spec 3.14). binary operators by precedence
+// climbing, each level reading its right side one level tighter.
+int cprec(int o) {
+	if (o == bname[0] || o == bname[1] || o == bname[2]) return 10;
+	if (o == bname[3] || o == bname[4]) return 9;
+	if (o == bname[5] || o == bname[6]) return 8;
+	if (o == bname[13]) return 5;
+	if (o == bname[14]) return 4;
+	if (o == bname[15]) return 3;
+	return 0;
+}
+int cbin(int minp) {
+	int v = cprim(), o, p, w;
 	while (tk == T_OP) {
-		o = tv;
-		if (o == bname[3]) { next(); v = v + cprim(); }
-		else if (o == bname[4]) { next(); v = v - cprim(); }
-		else if (o == bname[0]) { next(); v = v * cprim(); }
-		else if (o == bname[15]) { next(); v = v | cprim(); }
-		else if (o == bname[13]) { next(); v = v & cprim(); }
-		else if (o == bname[5]) { next(); v = v << cprim(); }
-		else if (o == bname[6]) { next(); v = v >> cprim(); }
-		else return v;
+		o = tv; p = cprec(o);
+		if (p == 0 || p < minp) return v;
+		next(); w = cbin(p + 1);
+		if (o == bname[0]) v = v * w;
+		else if (o == bname[1] || o == bname[2]) {
+			if (w == 0) { die("division by zero in a constant expression"); return 0; }
+			if (o == bname[1]) v = v / w; else v = v % w;
+		}
+		else if (o == bname[3]) v = v + w;
+		else if (o == bname[4]) v = v - w;
+		else if (o == bname[5]) v = v << w;
+		else if (o == bname[6]) v = v >> w;
+		else if (o == bname[13]) v = v & w;
+		else if (o == bname[14]) v = v ^ w;
+		else v = v | w;
 	}
 	return v;
 }
+int cexpr() { return cbin(1); }