Fetch stage properly holds objects until parent is ready

1 files changed, 22 insertions, 8 deletions

diff --git a/src/sim/if.cc b/src/sim/if.cc
index 099ff1c..de044f8 100644
--- a/src/sim/if.cc
+++ b/src/sim/if.cc
@@ -6,17 +6,31 @@
 
 IF::IF(Stage *stage) : Stage(stage) { this->id = FETCH; }
 
-Response IF::advance(InstrDTO &i, Response p)
+Response IF::advance(InstrDTO &next_instr, Response p)
+{
+	this->fetch_with_buffer();
+	if (this->status == OK && p == OK) {
+		// mutual consent
+		++this->pc;
+		this->curr_instr->set_time_of(this->id, this->clock_cycle);
+		next_instr = *this->curr_instr;
+		curr_instr = nullptr;
+	}
+	return this->status;
+}
+
+void IF::fetch_with_buffer()
 {
 	Response r;
 	signed int bits;
 
-	r = this->storage->read_word(this->id, this->pc, bits);
-	if (r == OK) {
-		++this->pc;
-		i.set_time_of(this->id, this->clock_cycle);
-		i.set_instr_bits(bits);
+	if (this->curr_instr == nullptr) {
+		r = this->storage->read_word(this->id, this->pc, bits);
+		if (r == OK) {
+			this->status = r;
+			this->curr_instr = std::make_unique<InstrDTO>();
+			this->curr_instr->set_instr_bits(bits);
+		} else
+			this->status = STALLED;
 	}
-
-	return r;
 }