Merge pull request #37 from bdunahu/bdunahu

Instr, InstrDTO gets/sets, other structures required for decode

-- tests as we move forward
-- base classes
-- decode stage implemented

1 files changed, 75 insertions, 3 deletions

diff --git a/inc/id.h b/inc/id.h
index de8f677..49637ce 100644
--- a/inc/id.h
+++ b/inc/id.h
@@ -1,5 +1,6 @@
 #ifndef ID_H
 #define ID_H
+#include "instr.h"
 #include "instrDTO.h"
 #include "response.h"
 #include "stage.h"
@@ -7,9 +8,80 @@
 class ID : public Stage
 {
   public:
-	using Stage::Stage;
+	/**
+	 * Constructor.
+	 * @param The next stage in the pipeline.
+	 * @return A newly allocated ID object.
+	 */
+	ID(Stage *next);
 
-	Response advance(InstrDTO &i) override;
+	Response advance(InstrDTO &next_instr, Response p) override;
+
+	/* The following methods are made public so that they may be tested, and are
+	 * not to be called from outside classes during standard execution.
+	 */
+
+	/**
+	 * Parse an instruction into a type, opcode, and fields. If the type is
+	 * invalid, only the type field will be set.
+	 *
+	 * This method is marked public so it may be tested, and is not used outside
+	 * of this class during normal execution.
+	 *
+	 * @param the resulting first field, which varies per type. To call this
+	 * function properly, this field must contain the full instruction bytes on
+	 * function entry.
+	 * @param the resulting second field, which varies per type.
+	 * @param the resulting third field, which varies per type.
+	 * @param the resulting mnemonic.
+	 */
+	void get_instr_fields(
+		signed int &s1, signed int &s2, signed int &s3, Mnemonic &m);
+	/**
+	 * Facilitates register checkout and data hazard management.
+	 * It does this by checking that the register passed in is not currently
+	 * checked out. If true, then replaces r with the value of the register and
+	 * returns OK. If false, returns STALLED.
+	 *
+	 * @param the registers number, to be dereferenced.
+	 * @return OK if `r` is not checked out, STALLED otherwise.
+	 */
+	Response read_guard(signed int &r);
+	/**
+	 * Facilitates register checkout and data hazard management.
+	 * Checks out a register and returns it.
+	 *
+	 * @param the registers number, to be dereferenced and checked out.
+	 */
+	void write_guard(signed int &r);
+
+  private:
+	/**
+	 * Decodes `curr_instr` and sets status to BLOCKED if a data hazard occurs.
+	 */
+	void advance_helper();
+	/**
+	 * Helper for `get_instr_fields`
+	 * Attempts to parse and dereference instruction arguments. Uses read and
+	 * write guards to prevent RAW conflicts.
+	 *
+	 * @param the resulting first field. To call this function properly, this
+	 * field must contain the section of the instruction to be parsed.
+	 * @param the resulting second field.
+	 * @param the resulting third field.
+	 */
+	void decode_R_type(signed int &s1, signed int &s2, signed int &s3);
+	void decode_I_type(signed int &s1, signed int &s2, signed int &s3);
+	void decode_J_type(signed int &s1, signed int &s2);
+	/**
+	 * Helper for `get_instr_fields`.
+	 * Given a raw instruction, returns the mnemonic and type.
+	 * This operation will destroy the original arguments.
+	 * @param the raw bits to parse.
+	 * @param the resulting mnemonic.
+	 * @param the resulting type.
+	 */
+	void split_instr(signed int &raw, unsigned int &type, Mnemonic &m);
 };
 
-#endif /* ID_D_INCLUDED */
+#endif /* ID_H_INCLUDED */