harec

commit aaee24a6426cac9490712aefe03221bbf6813e8d
parent 70b85a49d251e84a6954cc653a3036927110f9b1
Author: Drew DeVault <sir@cmpwn.com>
Date:   Tue,  2 Feb 2021 18:06:55 -0500

gen: more refactoring for match

Diffstat:
M
src/gen.c
 | 
98
+++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------

1 file changed, 63 insertions(+), 35 deletions(-)
diff --git a/src/gen.c b/src/gen.c
@@ -1480,12 +1480,53 @@ gen_expr_list(struct gen_context *ctx,
 }
 
 static void
+gen_recursive_match_tests(struct gen_context *ctx, const struct type *mtype,
+	struct qbe_value *fbranch, struct qbe_value *tag,
+	struct qbe_value *mval, struct match_case *_case)
+{
+	struct qbe_value temp = {0}, temp_tag = {0}, subval = {0}, offs = {0};
+	gen_temp(ctx, &subval, &qbe_long, "subtag.ptr.%d");
+	gen_temp(ctx, &temp_tag, &qbe_word, "subtag.tag.%d");
+	pushi(ctx->current, &subval, Q_COPY, mval, NULL);
+	gen_temp(ctx, &temp, &qbe_word, "temp.%d");
+
+	struct qbe_value *curtag = tag;
+	const struct type *subtype = mtype;
+	const struct type *test = _case->type;
+	do {
+		struct qbe_statement slabel = {0};
+		struct qbe_value sbranch = {0};
+		test = tagged_select_subtype(subtype, _case->type);
+		if (!test) {
+			break;
+		}
+
+		struct qbe_value match = {0};
+		sbranch.kind = QV_LABEL;
+		sbranch.name = strdup(genl(&slabel, &ctx->id, "match.subtype.%d"));
+		constw(&match, test->id);
+		pushi(ctx->current, &temp, Q_CEQW, &match, curtag, NULL);
+		pushi(ctx->current, NULL, Q_JNZ, &temp, &sbranch, fbranch, NULL);
+		push(&ctx->current->body, &slabel);
+
+		if (test->id != _case->type->id) {
+			constl(&offs, subtype->align);
+			pushi(ctx->current, &subval, Q_ADD, &subval, &offs, NULL);
+			pushi(ctx->current, &temp_tag, Q_LOADUW, &subval, NULL);
+			curtag = &temp_tag;
+		}
+
+		subtype = test;
+	} while (test->id != _case->type->id);
+}
+
+static void
 gen_match_tagged(struct gen_context *ctx,
 	const struct expression *expr,
 	const struct qbe_value *out)
 {
 	const struct type *mtype = expr->match.value->result;
-	struct qbe_value mval = {0}, tag = {0}, match = {0}, temp = {0};
+	struct qbe_value mval = {0}, tag = {0}, temp = {0};
 	// Kill me
 	alloc_temp(ctx, &mval, mtype, "match.%d");
 	qval_deref(&mval);
@@ -1515,40 +1556,22 @@ gen_match_tagged(struct gen_context *ctx,
 		fbranch.kind = QV_LABEL;
 		fbranch.name = strdup(genl(&flabel, &ctx->id, "next.case.%d"));
 
-		struct qbe_value temp_tag = {0}, subval = {0}, offs = {0};
-		gen_temp(ctx, &subval, &qbe_long, "subtag.ptr.%d");
-		gen_temp(ctx, &temp_tag, &qbe_word, "subtag.tag.%d");
-		pushi(ctx->current, &subval, Q_COPY, &mval, NULL);
-
-		struct qbe_value *curtag = &tag;
-		const struct type *subtype = mtype;
-		const struct type *test = _case->type;
-		do {
-			struct qbe_statement slabel = {0};
-			struct qbe_value sbranch = {0};
-			test = tagged_select_subtype(subtype, _case->type);
-			if (!test) {
-				assert(type_dealias(_case->type)->storage == TYPE_STORAGE_TAGGED);
-				assert(tagged_subset_compat(subtype, _case->type));
-				assert(0); // TODO
-			}
-
-			sbranch.kind = QV_LABEL;
-			sbranch.name = strdup(genl(&slabel, &ctx->id, "match.subtype.%d"));
-			constw(&match, test->id);
-			pushi(ctx->current, &temp, Q_CEQW, &match, curtag, NULL);
-			pushi(ctx->current, NULL, Q_JNZ, &temp, &sbranch, &fbranch, NULL);
-			push(&ctx->current->body, &slabel);
-
-			if (test->id != _case->type->id) {
-				constl(&offs, subtype->align);
-				pushi(ctx->current, &subval, Q_ADD, &subval, &offs, NULL);
-				pushi(ctx->current, &temp_tag, Q_LOADUW, &subval, NULL);
-				curtag = &temp_tag;
-			}
+		bool reinterpret = false;
+		if (tagged_select_subtype(mtype, _case->type) == NULL) {
+			assert(type_dealias(_case->type)->storage == TYPE_STORAGE_TAGGED);
+			assert(tagged_subset_compat(mtype, _case->type));
+			// Our match value can be "re-interpreted" as this case
+			// type because it is a subset-compatible tagged union.
+			// This causes later code to leave the pointer at the
+			// tag, rather than advancing it to the value area,
+			// before initializing a binding for it.
+			reinterpret = true;
+			assert(0); // TODO
+		} else {
+			gen_recursive_match_tests(ctx, mtype,
+				&fbranch, &tag, &mval, _case);
+		}
 
-			subtype = test;
-		} while (test->id != _case->type->id);
 		pushi(ctx->current, NULL, Q_JMP, &tbranch, NULL);
 
 		push(&ctx->current->body, &tlabel);
@@ -1565,7 +1588,12 @@ gen_match_tagged(struct gen_context *ctx,
 			ctx->bindings = binding;
 			constl(&temp, mtype->align);
 			val.type = &qbe_long;
-			pushi(ctx->current, &val, Q_ADD, &mval, &temp, NULL);
+			if (!reinterpret) {
+				pushi(ctx->current, &val, Q_ADD,
+					&mval, &temp, NULL);
+			} else {
+				pushi(ctx->current, &val, Q_COPY, &mval, NULL);
+			}
 		}
 
 		if (_case->value->terminates) {