mie: ir: implement generation and text output of phi instruction

mie/ir/phi.c

@@ -0,0 +1,19 @@
+#include <mie/ir/phi.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct mie_phi_edge *mie_phi_edge_create(
+	struct mie_block *incoming_block, struct mie_value *value)
+{
+	struct mie_phi_edge *out = malloc(sizeof *out);
+	if (!out) {
+		return NULL;
+	}
+
+	memset(out, 0x0, sizeof *out);
+
+	out->e_incoming_block = incoming_block;
+	out->e_value = value;
+
+	return out;
+}