scc

commit c33ee56f6924c8e0f4a06fd7c1d7e0b457660781
parent 2bc598101275d978b5494d034bd71d8e2b443f4a
Author: Roberto E. Vargas Caballero <k0ga@shike2.net>
Date:   Tue, 24 Mar 2026 09:27:14 +0100

cc1: Fix log value returned by power2node()

The function power2node() can optionally returns the log base 2
of the input parameter. That use case is not currently used, but
the code calculating the log was wrong and produced always 1.
Also, the code was optimized a bit to avoid more tests per bit.

Diffstat:
M
src/cmd/scc-cc/cc1/expr.c
 | 
11
++++-------

1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/src/cmd/scc-cc/cc1/expr.c b/src/cmd/scc-cc/cc1/expr.c
@@ -19,19 +19,16 @@ power2node(Node *np, int *log)
 		return 0;
 
 	sym = np->sym;
-	if (sym->type->op != INT)
+	if (sym->type->op != INT || (u = sym->u.u) == 0)
 		return 0;
 
-	n = 0;
-	for (u = sym->u.u; u; u >>= 1) {
-		if (u & 1)
-			n++;
-	}
+	for (n = 0; (u & 1) == 0; n++)
+		u >>= 1;
 
 	if (log)
 		*log = n;
 
-	return n == 1;
+	return u == 1;
 }
 
 int