expr: Handle compound assignment of bit-fields

3 files changed, 39 insertions, 1 deletions

diff --git a/expr.c b/expr.c
index f937947..28585c9 100644
--- a/expr.c
+++ b/expr.c
@@ -867,7 +867,7 @@ mkassignexpr(struct expr *l, struct expr *r)
 struct expr *
 assignexpr(struct scope *s)
 {
-	struct expr *e, *l, *r, *tmp;
+	struct expr *e, *l, *r, *tmp, *bit;
 	enum tokenkind op;
 
 	l = condexpr(s);
@@ -895,11 +895,21 @@ assignexpr(struct scope *s)
 	if (!op)
 		return mkassignexpr(l, r);
 	/* rewrite `E1 OP= E2` as `T = &E1, *T = *T OP E2`, where T is a temporary slot */
+	if (l->kind == EXPRBITFIELD) {
+		bit = l;
+		l = l->bitfield.base;
+	} else {
+		bit = NULL;
+	}
 	tmp = mkexpr(EXPRTEMP, mkpointertype(l->type, l->qual));
 	tmp->lvalue = true;
 	tmp->temp = NULL;
 	e = mkassignexpr(tmp, mkunaryexpr(TBAND, l));
 	l = mkunaryexpr(TMUL, tmp);
+	if (bit) {
+		bit->bitfield.base = l;
+		l = bit;
+	}
 	r = mkbinaryexpr(&tok.loc, op, l, r);
 	e->next = mkassignexpr(l, r);
 	l = mkexpr(EXPRCOMMA, l->type);
diff --git a/tests/bitfield-compound-assign.c b/tests/bitfield-compound-assign.c
new file mode 100644
index 0000000..5ca42e4
--- /dev/null
+++ b/tests/bitfield-compound-assign.c
@@ -0,0 +1,7 @@
+struct {
+	int : 4, x : 9, : 3;
+} s;
+
+void f(void) {
+	s.x += 3;
+}
diff --git a/tests/bitfield-compound-assign.qbe b/tests/bitfield-compound-assign.qbe
new file mode 100644
index 0000000..829f5f6
--- /dev/null
+++ b/tests/bitfield-compound-assign.qbe
@@ -0,0 +1,21 @@
+export
+function $f() {
+@start.1
+@body.2
+	%.1 =l copy $s
+	%.2 =l mul 0, 1
+	%.3 =l add %.1, %.2
+	%.4 =l copy %.3
+	%.5 =w loadsw %.4
+	%.6 =w shl %.5, 19
+	%.7 =w sar %.6, 23
+	%.8 =w add %.7, 3
+	%.9 =w loaduw %.4
+	%.10 =w and %.9, 18446744073709543439
+	%.11 =w shl %.8, 4
+	%.12 =w and %.11, 8176
+	%.13 =w or %.10, %.12
+	storew %.13, %.4
+	ret
+}
+export data $s = align 4 { z 4 }