bounds checking: constant loop bound proof works, plain-op fixed-array check, docs (readme, spec 4.15 and friends, server, vscode), conformance and test.sh fixes, todo

1 files changed, 8 insertions, 6 deletions

diff --git a/src/compiler/expr.zc b/src/compiler/expr.zc
index c76b74c..1536744 100644
--- a/src/compiler/expr.zc
+++ b/src/compiler/expr.zc
@@ -1322,12 +1322,14 @@ int range_jz(int ix, int src, int fld) {
 	return 0;
 }
 // the inline check of a fixed array T[n]: the index is on top of the stack and
-// stays there. one "outside" enhancement against the constant length and a
-// branch to the oob report, the same shape as range_jz.
+// stays there. i is outside 0..n-1 exactly when i | (n - 1 - i) is negative:
+// one subtract, one or and one compare, then a branch to the oob report. no
+// enhancement: the x86-64 jit calls one rather than inlining it.
 int fixed_chk(int n) {
-	int k = lookup(s_outside), j;
-	if (k < 0 || skind[k] != K_ENH) return 0;
-	lit(0); op(O_PICK); lit(n); op(XOP0 + sval[k]);
+	int j;
+	lit(0); op(O_PICK); lit(n - 1); op(O_SWAP); op(O_SUB);
+	lit(1); op(O_PICK); op(17);
+	lit(0); op(O_LT);
 	j = hole(); op(O_JZ);
 	lit(n); callname(s_oob);
 	setlit(j, here);
@@ -1753,7 +1755,7 @@ int bin(int minp) {
 		if (top) {
 			ft_nops++;
 			if (ft_nops > 1) ft_iv = -1;
-			else if (bname[b] == s_lt && blen[b] > 0 && il >= 0 && ft_ir >= 0 && !lf && !rf && !ls && !rs) { ft_iv = il; ft_bd = ft_ir; }
+			else if (bname[b] == s_lt && blen[b] > 0 && il >= 0 && (ft_ir >= 0 || ft_ck >= 0) && !lf && !rf && !ls && !rs) { ft_iv = il; ft_bd = ft_ir; }
 		}
 		lv = 0; lvk = LV_NONE; c = C_PLAIN; xzero = 0; xconst = 0; xlenloc = -1; xstamp = 0; xaf = 0; xvk = 0;
 		effect_value = 0; if (isptr(xty) || xty == tword) effect_value = left_mask | right_mask;