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

diff --git a/disas/nanomips.cpp b/disas/nanomips.cpp
index 06d2400284641980da44e9d3f994c6a3f8ea16a1..fe0c4af4cc35f793c62fdc44d46e70e372635063 100644 (file)
--- 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 };