scc

commit 0935ae49a658bedc97d1bf9082049498e148f6df
parent a8dae969ea1800fd5f3f247cc3cc7c91f10be260
Author: Roberto E. Vargas Caballero <k0ga@shike2.net>
Date:   Mon, 23 Mar 2026 11:54:51 +0100

cc1: Reduce unsigned constant division to shift

Diffstat:
M
src/cmd/scc-cc/cc1/fold.c
 | 
5
+++++
A
tests/cc/execute/0250-div.c
 | 
14
++++++++++++++
M
tests/cc/execute/scc-tests.lst
 | 
1
+

3 files changed, 20 insertions(+), 0 deletions(-)
diff --git a/src/cmd/scc-cc/cc1/fold.c b/src/cmd/scc-cc/cc1/fold.c
@@ -803,6 +803,11 @@ reduce(Node *np)
 		return;
 
 	switch (op) {
+	case ODIV:
+		/* i / 2^n => i >> n */
+		np->op = OSHR;
+		rp->sym->u.u = log;
+		break;
 	case OMOD:
 		/* i % 2^n => i & n-1 */
 		np->op = OBAND;
diff --git a/tests/cc/execute/0250-div.c b/tests/cc/execute/0250-div.c
@@ -0,0 +1,14 @@
+int
+main(void)
+{
+	int a = -2;
+	unsigned b = 2, c = 16;
+
+	if (!(a / 2 == -1))
+		return 1;
+	if (!(b / 2 == 1))
+		return 2;
+	if (!(c / 8 == 2))
+		return 3;
+	return 0;
+}
diff --git a/tests/cc/execute/scc-tests.lst b/tests/cc/execute/scc-tests.lst
@@ -240,3 +240,4 @@
 0247-float.c
 0248-enum.c
 0249-mod.c
+0250-div.c