On 01/06/2013 03:56 PM, "Jürgen Urban" wrote:
Hello,
I created a patch from scratch to support MIPS r5900 used in the
Playstation 2, but I have some problems with it. The attached patch
only works with the latest binutils from CVS. The binutils forces the
compiler to use r5900 compatible instructions which is good to find
errors in the GCC. Later I will try to submit a patch here, but first
I need some help. The MIPS r5900 supports 32 bit, 64 bit and 128 bit
data accesses on a 32 Bit address bus. It supports instructions from
MIPS ISA I, II, III, IV and has additional instructions, but none of
them are complete. On each ISA level there are instructions missing.
It can run MIPS ABI o32, n32 and o64 code, as long as unsupported
instructions are not used or emulated by the operating system and the
addresses keep in the first 32 bit. My patch adds support for r5900
and tries to disable the following unsupported instructions: ll, sc,
dmult, ddiv, cvt.w.s, 64 bit FPU instructions. ll and sc is disabled
with "-mno-llsc" and works. cvt.w.s is replaced by trunc.w.s. This
seems to work. I disabled 64 bit FPU instructions by "-msoft-float".
This works, but using "-msingle-float" fails. This would be the
better configuration. There are still 64 bit FPU instructions used
(e.g. "dmfc1 $2,$f0" when using "long double" multiplication). So
"-msingle-float" doesn't seem to work on generic mips64-linux-gnu. I
tried to disable dmult and ddiv (see mips.md). Disabling worked, but
now muldi3 calls itself in libgcc2. I thought this should work,
because I got this working with GCC 4.3, but the latest GCC version
is a problem. multi3 is calling muldi3, so that muldi3 should be able
to use mulsi3, because it is the same C code in libgcc2. Can someone
get me some hints or comments? How can this be debugged?
Does someone know how to enable TImode in MIPS ABI o32 (this doesn't
need to use the 128 bit instructions at the moment)? There is some
old code for the Playstation 2 which needs this. I know that TImode
is supported in ABI n32, but some code uses also the 32 bit FPU and
FPU registers are not available with "-msoft-float" in inline
assembler.
What is the best way to change the alignment to 128 bit for all
structures and stack in any MIPS ABI? Much old code for the
Playstation 2 expects this.
Hmm, I did a R5900 port back in the late 90s... Did that port never get
contributed (yes, my memory is that bad these days)
As far as getting TI mode working, IIRC I did a configury hack of some
sort to force using a 64bit host wide integer, that in turn made it
possible to support TImode as a pair of 64bit HWIs.
As far as aligning structures and the stack, GCC has a standard set of
macros to define structure & stack alignment.
Jeff
