disas: nanoMIPS: Comment the decoder of 'gpr2.reg1' gpr encoding type

Comment the decoder of 'gpr2.reg1' gpr encoding type in nanoMIPS
disassembler.

Reviewed-by: Aleksandar Rikalo <arikalo@wavecomp.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>

diff --git a/disas/nanomips.cpp b/disas/nanomips.cpp
index b0d0cf890120f1a42c7cabb141e9f449fdac7563..c3b2bec943a8a9e5d693418d5b81501ef81f8470 100644 (file)
--- a/disas/nanomips.cpp
+++ b/disas/nanomips.cpp
@@ -468,6 +468,28 @@ uint64 NMD::decode_gpr_gpr4(uint64 d)
 }
 
 
+/*
+ * NMD::decode_gpr_gpr2_reg1() - decoder for 'gpr2.reg1' 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_reg1(uint64 d)
 {
     static uint64 register_list[] = {  4,  5,  6,  7 };