Setting condition code register, overflow guard

4 files changed, 42 insertions, 1 deletions

diff --git a/inc/definitions.h b/inc/definitions.h
index 3238a8b..c81c4e3 100644
--- a/inc/definitions.h
+++ b/inc/definitions.h
@@ -77,6 +77,12 @@
 #define OPCODE_SIZE 4
 
 /**
+ * The maximum value an integer can hold.
+ * The minimum is always this number plus one negated.
+ */
+#define MAX_INT 2147483647
+
+/**
  * Return the N least-significant bits from integer K using a bit mask
  * @param the integer to be parsed
  * @param the number of bits to be parsed
diff --git a/inc/ex.h b/inc/ex.h
index 2ca8876..4edf873 100644
--- a/inc/ex.h
+++ b/inc/ex.h
@@ -3,6 +3,7 @@
 #include "instrDTO.h"
 #include "response.h"
 #include "stage.h"
+#include <unordered_map>
 
 class EX : public Stage
 {
@@ -15,6 +16,23 @@ class EX : public Stage
 	EX(Stage *next);
 
 	InstrDTO *advance(Response p) override;
+
+  private:
+	/**
+	 * Sets the (over|under)flow condition code if adding `a` and `b` results in
+	 * either.
+	 * @param the first operand
+	 * @param the second operand
+	 */
+	void overflow_guard(signed int a, signed int b);
+	/**
+	 * Maps each mnemonic to a function which carries out the instruction's base
+	 * logic.
+	 */
+	std::unordered_map<
+		Mnemonic,
+		std::function<void(signed int &s1, signed int &s2)>>
+		instr_map;
 };
 
 #endif /* EX_H_INCLUDED */
diff --git a/inc/instr.h b/inc/instr.h
index 08b4fd0..7fbb42b 100644
--- a/inc/instr.h
+++ b/inc/instr.h
@@ -49,7 +49,6 @@ namespace instr
 {
 // clang-format off
 	extern const std::unordered_map<unsigned int, Mnemonic> mnemonic_map;
-	extern const std::unordered_map<Mnemonic, std::function<void(signed int &s1, signed int &s2, signed int &s3)>> instr_map;
 // clang-format on
 } // namespace instr
 
diff --git a/inc/stage.h b/inc/stage.h
index 50c413a..c0dc6a8 100644
--- a/inc/stage.h
+++ b/inc/stage.h
@@ -9,6 +9,13 @@
 #include <deque>
 #include <memory>
 
+enum CC {
+	GT,
+	EQ,
+	UF,
+	OF,
+};
+
 class Stage
 {
   public:
@@ -31,6 +38,17 @@ class Stage
 
   protected:
 	/**
+	 * Sets the bit in the condition code register corresponding to `c`.
+	 * @param the condition code to set.
+	 * @param the truthy value to set it to.
+	 */
+	void set_condition(CC c, bool v);
+	/**
+	 * Gets the bit in the condition code register correspondng to `c`.
+	 * @param the condition code to retrieve,
+	 */
+	bool get_condition(CC c);
+	/**
 	 * Helper for `check_out`.
 	 * Returns true if r are not checked out, false otherwise.
 	 * @param a list of register numbers.