Make member access its own expression type

4 files changed, 25 insertions, 21 deletions

diff --git a/expr.c b/expr.c
index d30669c..629ae22 100644
--- a/expr.c
+++ b/expr.c
@@ -483,9 +483,7 @@ postfixexpr(struct scope *s, struct expr *r)
 	struct type *t;
 	enum typequal tq;
 	struct param *p;
-	uint64_t offset;
 	enum tokenkind op;
-	bool lvalue;
 
 	if (!r)
 		r = primaryexpr(s);
@@ -566,17 +564,19 @@ postfixexpr(struct scope *s, struct expr *r)
 			next();
 			if (tok.kind != TIDENT)
 				error(&tok.loc, "expected identifier after '->' operator");
-			lvalue = op == TARROW || r->unary.base->flags & EXPRFLAG_LVAL;
-			r = exprconvert(r, mkpointertype(&typechar));
-			offset = 0;
-			t = typemember(t, tok.lit, &offset);
-			if (!t)
+			e = mkexpr(EXPRMEMBER, NULL, 0);
+			e->member.base = r;
+			e->member.offset = 0;
+			e->type = typemember(t, tok.lit, &e->member.offset);
+			if (!e->type)
 				error(&tok.loc, "struct/union has no member named '%s'", tok.lit);
-			r = mkbinaryexpr(&tok.loc, TADD, r, mkconstexpr(&typeulong, offset));
-			r = exprconvert(r, mkpointertype(mkqualifiedtype(t, tq)));
-			e = mkunaryexpr(TMUL, r);
-			if (!lvalue)
-				e->flags &= ~EXPRFLAG_LVAL;
+			if (op == TARROW || r->unary.base->flags & EXPRFLAG_LVAL) {
+				e->type = mkqualifiedtype(e->type, tq);
+				e->flags |= EXPRFLAG_LVAL;
+			} else {
+				e->type = typeunqual(e->type, NULL);
+			}
+			e = decay(e);
 			next();
 			break;
 		case TINC:
diff --git a/expr.h b/expr.h
index e660848..5667839 100644
--- a/expr.h
+++ b/expr.h
@@ -6,7 +6,7 @@ enum exprkind {
 
 	/* postfix expression */
 	EXPRCALL,
-	/* member E.M gets transformed to *(typeof(E.M) *)((char *)E + offsetof(typeof(E), M)) */
+	EXPRMEMBER,
 	EXPRINCDEC,
 	EXPRCOMPOUND,
 	/* subscript E1[E2] gets transformed to *((E1)+(E2)) */
@@ -49,14 +49,18 @@ struct expr {
 			size_t nargs;
 		} call;
 		struct {
-			struct init *init;
-		} compound;
+			struct expr *base;
+			size_t offset;
+		} member;
 		struct {
 			int op;
 			_Bool post;
 			struct expr *base;
 		} incdec;
 		struct {
+			struct init *init;
+		} compound;
+		struct {
 			int op;
 			struct expr *base;
 		} unary;
diff --git a/qbe.c b/qbe.c
index a40540a..66cc271 100644
--- a/qbe.c
+++ b/qbe.c
@@ -479,6 +479,8 @@ objectaddr(struct func *f, struct expr *e)
 	case EXPRSTRING:
 		d = stringdecl(e);
 		return d->value;
+	case EXPRMEMBER:
+		return funcinst(f, IADD, &iptr, funcexpr(f, e->member.base), mkintconst(&iptr, e->member.offset));
 	case EXPRCOMPOUND:
 		d = mkdecl(DECLOBJECT, e->type, LINKNONE);
 		funcinit(f, d, e->compound.init);
@@ -599,6 +601,7 @@ funcexpr(struct func *f, struct expr *e)
 		if (typeprop(e->type) & PROPINT || e->type->kind == TYPEPOINTER)
 			return mkintconst(e->type->repr, e->constant.i);
 		return mkfltconst(e->type->repr, e->constant.f);
+	case EXPRMEMBER:
 	case EXPRCOMPOUND:
 		l = objectaddr(f, e);
 		return funcload(f, e->type, l);
diff --git a/tests/struct-return-2.qbe b/tests/struct-return-2.qbe
index 415ec2f..b1990ec 100644
--- a/tests/struct-return-2.qbe
+++ b/tests/struct-return-2.qbe
@@ -5,10 +5,7 @@ function w $f() {
 @body.2
 	%.1 =:.1 call $g()
 	%.2 =l copy %.1
-	%.3 =l copy %.2
-	%.4 =l mul 4, 1
-	%.5 =l add %.3, %.4
-	%.6 =l copy %.5
-	%.7 =w loadsw %.6
-	ret %.7
+	%.3 =l add %.2, 4
+	%.4 =w loadsw %.3
+	ret %.4
 }