[Qemu-devel] Question about comment on MIPS POOL32AXF encoding

[Qemu-devel] Question about comment on MIPS POOL32AXF encoding

[陳韋任 (Wei-Ren Chen)]

Hi all,

  I am reading POOL32AXF encoding in target-mips/translate.c,
and can't understand what the comment says. For example,

    /* bits 13..12 for 0x01 */
    MFHI_ACC = 0x0,
    MFLO_ACC = 0x1,
    MTHI_ACC = 0x2,
    MTLO_ACC = 0x3,

I compare this with microMIPS32 manual [1] Table 6.5, but I still
don't understand why they're encoded in such way. The comment says
"bits 13..12 for 0x01", I can roughly understand the enum list
bits 13..12 here, but what "for 0x01" exactly means?

  Thanks.

Regards,
chenwj

[1] MIPS Architecture for Programmers Volume II-B:
      The microMIPS32 Instruction Set

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj

Re: [Qemu-devel] Question about comment on MIPS POOL32AXF encoding

[Johnson, Eric]

> -----Original Message-----
> From: qemu-devel-bounces+ericj=mips.com@nongnu.org [mailto:qemu-devel-
> bounces+ericj=mips.com@nongnu.org] On Behalf Of ??? (Wei-Ren Chen)
> Sent: Thursday, November 15, 2012 1:03 AM
> To: qemu-devel@nongnu.org
> Cc: Jia Liu
> Subject: [Qemu-devel] Question about comment on MIPS POOL32AXF encoding
> 
> Hi all,
> 
>   I am reading POOL32AXF encoding in target-mips/translate.c,
> and can't understand what the comment says. For example,
> 
>     /* bits 13..12 for 0x01 */
>     MFHI_ACC = 0x0,
>     MFLO_ACC = 0x1,
>     MTHI_ACC = 0x2,
>     MTLO_ACC = 0x3,
> 
> I compare this with microMIPS32 manual [1] Table 6.5, but I still
> don't understand why they're encoded in such way. The comment says
> "bits 13..12 for 0x01", I can roughly understand the enum list
> bits 13..12 here, but what "for 0x01" exactly means?

Please refer to the following document.

MIPS® Architecture for Programmers VolumeIV-e: The MIPS® DSP Application-Specific Extension to the microMIPS32™ Architecture

http://www.mips.com/secure-download/index.dot?product_name=/auth/MD00764-2B-microMIPS32DSP-AFP-02.34.pdf

-Eric

Re: [Qemu-devel] Question about comment on MIPS POOL32AXF encoding

[陳韋任 (Wei-Ren Chen)]

> Please refer to the following document.
> 
> MIPS® Architecture for Programmers VolumeIV-e: The MIPS® DSP Application-Specific Extension to the microMIPS32™ Architecture
> 
> http://www.mips.com/secure-download/index.dot?product_name=/auth/MD00764-2B-microMIPS32DSP-AFP-02.34.pdf

  Thanks, Eric. I would like to add a comment here to remind
me where they come. :)

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj