disas: nanoMIPS: Comment the decoder of 'gpr2.reg2' gpr encoding type

Comment the decoder of 'gpr2.reg2' gpr encoding type in nanoMIPS disassembler. Reviewed-by: Aleksandar Rikalo <[email protected]> Signed-off-by: Aleksandar Markovic <[email protected]>
zhijianli88 · Jan 3, 2019 · a21e052 · a21e052
1 parent ce0f261
commit a21e052
Showing 1 changed file with 22 additions and 0 deletions.
diff --git a/disas/nanomips.cpp b/disas/nanomips.cpp
@@ -498,6 +498,28 @@ uint64 NMD::decode_gpr_gpr2_reg1(uint64 d)
 }
 
 
+/*
+ * NMD::decode_gpr_gpr2_reg2() - decoder for 'gpr2.reg2' gpr encoding type
+ *
+ *   Map a 2-bit code to the 5-bit register space according to this pattern:
+ *
+ *                                3 2 1 0
+ *                                | | | |
+ *                                | | | |
+ *                                | | | └-----------------┐
+ *                                | | └-----------------┐ |
+ *                                | └-----------------┐ | |
+ *                                └-----------------┐ | | |
+ *                                                  | | | |
+ *                                                  | | | |
+ *    1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+ *      3                   2                   1                   0
+ *
+ *   Used in handling following instructions:
+ *
+ *     - MOVEP
+ *     - MOVEP[REV]
+ */
 uint64 NMD::decode_gpr_gpr2_reg2(uint64 d)
 {
     static uint64 register_list[] = {  5,  6,  7,  8 };