Build fails on mips n32

[GoogleCodeExporter]

What steps will reproduce the problem?
1. build libyuv (the one bundled with firefox, in my case)

What is the expected output? What do you see instead?
Build fails because the mips assembly in libyuv does not support the N32 ABI; 
gas is complaining about non-existent registers from $t4 to $t7

What version of the product are you using? On what operating system?
Firefox 30, Gentoo linux MIPS N32

Please provide any additional information below.
I workarounded this by uncommenting LIBYUV_DISABLE_MIPS. Some code should be 
added to detect ABI, or an mips n32 port should be made (mips64 might also 
benefit from this).

Original issue reported on code.google.com by wenbin...@gmail.com on 15 Jun 2014 at 2:18

[GoogleCodeExporter]

It looks like this is how to detect -n32
#if (_MIPS_SIM == _MIPS_SIM_ABI32)

$t4 to $t7 still exist under N32... not clear why its complaining?

Original comment by fbarch...@chromium.org on 16 Jun 2014 at 10:53

• Changed state: Accepted

[GoogleCodeExporter]

According to wikipedia[1], $12 to $15 are called $t4 to $t7. But it seems that 
the GNU toolchain is calling them $t0 to $t3[2], so a line containing $t4 to 
$t7 generates error like "invalid operator in 'lw $t4, 16(%[src])'", but $t0 to 
$t3 passes.

[1] http://en.wikipedia.org/wiki/MIPS_instruction_set
[2] https://www.sourceware.org/ml/gdb-patches/2003-03/msg00416.html

Original comment by wenbin...@gmail.com on 20 Jun 2014 at 8:59

[GoogleCodeExporter]

So n32/n64 lost t4 - t7 and gains a4 - a7.
Some functions could use a4-a7, depending on number of args.
This may be efficient, but won't build with o32

Some functions that dont use all the 's' registers could use those instead.
portable, but will cause push/pop to preserve them.

Some use all the 't' and 's' and have many args:
void TransposeWx8_FAST_MIPS_DSPR2(const uint8* src, int src_stride,
                                  uint8* dst, int dst_stride,
                                  int width) {
      : "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9",
        "s0", "s1", "s2", "s3", "s4", "s5", "s6", "s7"
lets start with only enabling the assembly for old 32 bit ABI.

Original comment by fbarch...@chromium.org on 24 Jun 2014 at 11:06

[GoogleCodeExporter]

This is the CL to only enable mips assembly with old 32 bit ABI.
https://webrtc-codereview.appspot.com/20769005
checked in as r1020
Are you able to confirm it builds?

Original comment by fbarch...@chromium.org on 24 Jun 2014 at 11:41

• Changed state: Started

[GoogleCodeExporter]

Original comment by fbarch...@chromium.org on 27 Jun 2014 at 12:57

• Changed state: Fixed