BGEZAL

Both PSX-SPX and the R3000 manual specify these instructions as having the following encoding:

000001 | rs   | 00000| <--immediate16bit--> | bltz
000001 | rs   | 00001| <--immediate16bit--> | bgez
000001 | rs   | 10000| <--immediate16bit--> | bltzal
000001 | rs   | 10001| <--immediate16bit--> | bgezal

This is only partially correct. The true encoding is the following:

000001 | rs   | xxxx0| <--immediate16bit--> | bltz
000001 | rs   | xxxx1| <--immediate16bit--> | bgez
000001 | rs   | 10000| <--immediate16bit--> | bltzal
000001 | rs   | 10001| <--immediate16bit--> | bgezal

Where xxxx is any bit sequence other than 1000.

This behaviour is required for passing the b_0xXX_y tests in Amidog's CPU test.

PSX Notes

Encoding of BLTZ/BGEZ/BLTZAL/BGEZAL