cpu: Change literal integer constants to meaningful labels

fu_pool and inst_queue were using -1 for "no such FU" and -2 for "all those
FUs are busy at the moment" when requesting for a FU and replying. This
patch introduces new constants NoCapableFU and NoFreeFU respectively.

In addition, the condition (idx == -2 || idx != -1) is equivalent to
(idx != -1), so this patch also simplifies that.

--HG--
extra : rebase_source : 4833717b9d1e09d7594d1f34f882e13fc4b86846

1 files changed, 9 insertions, 4 deletions

diff --git a/src/cpu/o3/fu_pool.hh b/src/cpu/o3/fu_pool.hh
index e6bb8cb8e..b6e9c126a 100644
--- a/src/cpu/o3/fu_pool.hh
+++ b/src/cpu/o3/fu_pool.hh
@@ -134,12 +134,17 @@ class FUPool : public SimObject
     FUPool(const Params *p);
     ~FUPool();
 
+    static constexpr auto NoCapableFU = -2;
+    static constexpr auto NoFreeFU = -1;
     /**
-     * Gets a FU providing the requested capability. Will mark the unit as busy,
-     * but leaves the freeing of the unit up to the IEW stage.
+     * Gets a FU providing the requested capability. Will mark the
+     * unit as busy, but leaves the freeing of the unit up to the IEW
+     * stage.
+     *
      * @param capability The capability requested.
-     * @return Returns -2 if the FU pool does not have the capability, -1 if
-     * there is no free FU, and the FU's index otherwise.
+     * @return Returns NoCapableFU if the FU pool does not have the
+     * capability, NoFreeFU if there is no free FU, and the FU's index
+     * otherwise.
      */
     int getUnit(OpClass capability);