lang: codegen: cond: implement implicitly returning values from an if-else expression

lang/codegen/cond-group.c

@@ -1,8 +1,10 @@
 #include "../debug.h"
 #include "codegen.h"
 
+#include <assert.h>
 #include <mie/ir/block.h>
 #include <mie/ir/func.h>
+#include <mie/ir/phi.h>
 #include <mie/ir/value.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -11,6 +13,7 @@
 struct cond_group_codegen_state {
 	struct code_generator_state s_base;
 	struct mie_block *s_end;
+	b_queue s_edges;
 };
 
 static struct code_generator_result gen_cond_group(
@@ -46,6 +49,65 @@ static enum ivy_status state_init(
 	return IVY_OK;
 }
 
+static enum ivy_status get_eval_type(
+	struct ivy_codegen *gen, struct cond_group_codegen_state *state,
+	struct mie_type **out)
+{
+	struct mie_type *type = NULL;
+
+	b_queue_iterator it;
+	b_queue_foreach (&it, &state->s_edges) {
+		struct mie_phi_edge *edge
+			= b_unbox(struct mie_phi_edge, it.entry, e_entry);
+		if (!edge->e_value) {
+			continue;
+		}
+
+		struct mie_type *edge_type
+			= mie_value_get_type(edge->e_value, gen->c_ctx);
+
+		if (!type) {
+			type = edge_type;
+			continue;
+		}
+	}
+
+	*out = type;
+	return IVY_OK;
+}
+
+static enum ivy_status emit_phi_instr(
+	struct ivy_codegen *gen, struct cond_group_codegen_state *state,
+	struct mie_type *type, struct mie_value **result)
+{
+	size_t nr_edges = b_queue_length(&state->s_edges);
+	if (!nr_edges) {
+		return IVY_OK;
+	}
+
+	struct mie_phi_edge *edges = calloc(nr_edges, sizeof *edges);
+	if (!edges) {
+		return IVY_ERR_NO_MEMORY;
+	}
+
+	size_t i = 0;
+
+	b_queue_iterator it;
+	b_queue_foreach (&it, &state->s_edges) {
+		struct mie_phi_edge *edge
+			= b_unbox(struct mie_phi_edge, it.entry, e_entry);
+
+		memcpy(&edges[i], edge, sizeof *edge);
+		i++;
+	}
+
+	struct mie_value *phi = mie_builder_phi(
+		gen->c_builder, type, edges, nr_edges, "if.result");
+	*result = phi;
+
+	return IVY_OK;
+}
+
 static enum ivy_status state_fini(
 	struct ivy_codegen *gen, struct code_generator_state *state,
 	struct code_generator_value *result)
@@ -56,6 +118,12 @@ static enum ivy_status state_fini(
 	struct mie_func *func = mie_builder_get_current_func(gen->c_builder);
 	struct mie_block *block = mie_builder_get_current_block(gen->c_builder);
 
+	struct mie_type *result_type = NULL;
+	enum ivy_status status = get_eval_type(gen, group, &result_type);
+	if (status != IVY_OK) {
+		return status;
+	}
+
 	if (!block->b_terminator) {
 		mie_builder_br(gen->c_builder, group->s_end);
 	}
@@ -63,6 +131,19 @@ static enum ivy_status state_fini(
 	mie_func_insert_block(func, group->s_end, NULL);
 	mie_builder_set_insert_point(gen->c_builder, group->s_end);
 
+	struct mie_value *phi = NULL;
+	if (result_type) {
+		status = emit_phi_instr(gen, group, result_type, &phi);
+	}
+
+	if (status != IVY_OK) {
+		return status;
+	}
+
+	if (phi) {
+		code_generator_value_set_mie_value(result, phi);
+	}
+
 	return IVY_OK;
 }
 
@@ -72,6 +153,11 @@ static struct code_generator_result value_received(
 {
 	struct cond_group_codegen_state *cond
 		= (struct cond_group_codegen_state *)state;
+	assert(value->v_type == CODE_GENERATOR_VALUE_PHI_EDGE);
+
+	struct mie_phi_edge *edge = code_generator_value_get_phi_edge(value);
+	b_queue_push_back(&cond->s_edges, &edge->e_entry);
+
 	return CODEGEN_RESULT_OK(0);
 }
 

lang/codegen/cond.c

@@ -2,13 +2,16 @@
 #include "codegen.h"
 
 #include <mie/ir/func.h>
+#include <mie/ir/phi.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 struct cond_codegen_state {
 	struct code_generator_state s_base;
+	bool s_is_else;
 	struct mie_value *s_cond;
+	struct mie_value *s_result;
 	struct mie_block *s_true;
 	struct mie_block *s_false;
 	struct mie_block *s_end;
@@ -19,6 +22,8 @@ static struct code_generator_result gen_cond(
 	struct ivy_ast_node *node, size_t depth)
 {
 	struct cond_codegen_state *cond = (struct cond_codegen_state *)state;
+	struct ivy_ast_cond_node *cond_node = (struct ivy_ast_cond_node *)node;
+	cond->s_is_else = (cond_node->n_cond == NULL);
 	return CODEGEN_RESULT_OK(0);
 }
 
@@ -42,7 +47,6 @@ static struct code_generator_result gen_expr(
 	}
 
 	codegen_push_generator(gen, CODE_GENERATOR_EXPR, 0, NULL);
-
 	return CODEGEN_RESULT_OK(CODEGEN_R_REPEAT_NODE);
 }
 
@@ -84,7 +88,11 @@ static enum ivy_status state_fini(
 	debug_printf("codegen: end of cond\n");
 	struct cond_codegen_state *cond = (struct cond_codegen_state *)state;
 	struct mie_func *func = mie_builder_get_current_func(gen->c_builder);
+	struct mie_block *block = mie_builder_get_current_block(gen->c_builder);
 
+	struct mie_phi_edge *edge = mie_phi_edge_create(block, cond->s_result);
+
+	code_generator_value_set_phi_edge(result, edge);
 	mie_builder_br(gen->c_builder, cond->s_end);
 
 	if (cond->s_false) {
@@ -95,15 +103,10 @@ static enum ivy_status state_fini(
 	return IVY_OK;
 }
 
-static struct code_generator_result value_received(
+static void set_cond(
-	struct ivy_codegen *gen, struct code_generator_state *state,
+	struct ivy_codegen *gen, struct cond_codegen_state *cond,
 	struct mie_value *value)
 {
-	struct cond_codegen_state *cond = (struct cond_codegen_state *)state;
-	if (!value) {
-		return CODEGEN_RESULT_OK(0);
-	}
-
 	struct mie_type *cond_type = mie_value_get_type(value, gen->c_ctx);
 
 	if (cond_type->t_id == MIE_TYPE_INT && cond_type->t_width == 1) {
@@ -115,18 +118,40 @@ static struct code_generator_result value_received(
 			= mie_builder_cmp_neq(gen->c_builder, value, zero, NULL);
 		cond->s_cond = cmp;
 	}
+}
+
+static struct code_generator_result value_received(
+	struct ivy_codegen *gen, struct code_generator_state *state,
+	struct code_generator_value *value)
+{
+	struct cond_codegen_state *cond = (struct cond_codegen_state *)state;
+	if (!value) {
+		return CODEGEN_RESULT_OK(0);
+	}
+
+	if (!cond->s_is_else && !cond->s_cond) {
+		set_cond(gen, cond, code_generator_value_get_mie_value(value));
+		return CODEGEN_RESULT_OK(0);
+	}
+
+	if (!cond->s_result) {
+		cond->s_result = code_generator_value_get_mie_value(value);
+	}
 
 	return CODEGEN_RESULT_OK(0);
 }
 
-struct code_generator cond_generator
+struct code_generator cond_generator = {
-	= {.g_type = CODE_GENERATOR_COND,
+	.g_type = CODE_GENERATOR_COND,
-           .g_state_size = sizeof(struct cond_codegen_state),
+	.g_state_size = sizeof(struct cond_codegen_state),
-           .g_state_init = state_init,
+	.g_state_init = state_init,
-           .g_state_fini = state_fini,
+	.g_state_fini = state_fini,
-           .g_value_received = value_received,
+	.g_value_received = value_received,
-           .g_expr_generator = gen_expr,
+	.g_expr_generator = gen_expr,
-           .g_node_generators = {
+	.g_node_generators = {
-		   NODE_CODEGEN(COND, gen_cond),
+		NODE_CODEGEN(COND, gen_cond),
-		   NODE_CODEGEN(BLOCK, gen_block),
+		NODE_CODEGEN(BLOCK, gen_block),
-	   }};
+		NODE_CODEGEN(LOOP_BREAK, gen_block),
+		NODE_CODEGEN(LOOP_REPEAT, gen_block),
+	},
+};