Basic support for MIPS r5900

"Jürgen Urban" <JuergenUrban@gmx.de> writes:
> after some months I reworked the patch for r5900. It would be nice if
> this could be accepted. The patch contains only changes to get basic
> support for MIPS r5900. It can be used to compile a working Linux kernel
> for the Playstation 2. It is also possible to get Linux programs working
> with software floating point and ABI o32. Other stuff like hardware
> floating point and ABI n32 is not fully supported yet.

Thanks, looks good.  The comments I have are only minor and seemed easier
to spell out as a revised patch, attached below.  The changes are:

* removing the config.sub bit, which looked redundant.  We already have
  the up-to-date upstream config.sub.

* removing the target_cpu_default setting.  I realise this was taken
  from mips64-elf, but it was redundant here, there, and elsewhere.
  I've just committed a patch to remove the existing cases.

* removing the TUNE_5900 definition.  I prefer not to define these
  kinds of macro until they're used.

* removing the ISA_HAS_LDC1_SDC1 setting.  I realise what you did
  describes the reality of the processor, but the problem is that
  the patch doesn't provide an alternative for 64-bit loads and
  stores when -mfp64 is used.  That combination also isn't rejected,
  so we're likely to get an internal compiler error instead.

  This change shouldn't affect the soft-float case you describe.
  It also shouldn't be important for the single-float code.

* tweaking the mips_reorg_process_insns comment slightly

* fixing a few minor formatting issues

Does this version look OK to you?  I'll commit it if so.

> How much other changes will be currently accepted here? There is other
> stuff which I want to prepare and submit here, e.g.:
> 1. disable use of dmult and ddiv (ABI n32).
> 2. use trunc.w.s instead of cvt.w.s (to get single float working for
> normal range calculations; i.e. calculating without inf or nan).
> 3. fix use of ll/sc in libgomp, either increase mips ISA level or use
> syscall (which is broken in Linux 2.6.35.4).
> 4. fix libgcc to build a real muldi3 function for ABI n32 (not the
> multi3 function which is stored in muldi3.o file).
> 5. add support for configure parameters --float=single and
> --float=double in addition to --float=soft and --float=hard.
> 6. rework floating point to support single float with ABI n32 (either
> break the ABI or store floating point values in general purpose
> registers like soft float).
> 7. change libgcc or mips.md in way so that the non IEEE 754 compatible
> FPU of the r5900 gets compatible.

Well, I'm afraid that's hard to say in advance.  It really depends
on what the changes look like.  (1) and (2) sound harmless enough,
although (1) should probably only be done in conjunction with (4).
I'm not sure what (3) involves.  (5) sounds like a good idea.
(6) is worth doing, but anything ABI-related gets extra-paranoid
treatment. :-)

I'm not sure about (7) though.  I'd imagine trying to get true IEEE
conformance out of the R5900 FPU would be pretty difficult and carry
quite a bit of runtime overhead, especially with the subnormal handling.
Is it really worth it?  Do you have any particular use cases in mind?

FWIW, the Cygnus/Red Hat version of the port just stuck with the R5900
behaviour and made GCC understand it (MODE_HAS_* & various other bits).
This code was then updated and extended for the SPU.  I'd have expected
the support to be in reasonably good shape because of the SPU.

Thanks,
Richard

gcc/
2013-06-03  Jürgen Urban  <JuergenUrban@gmx.de>

	* config.gcc (mipsr5900-*-elf*, mipsr5900el-*-elf*, mips64r5900-*-elf*)
	(mips64r5900el-*-elf*): New configurations.
	* config/mips/mips-cpus.def (r5900): New processor.
	* config/mips/mips-tables.opt: Regenerate.
	* config/mips/mips.c (mips_rtx_cost_data): Add an R5900 entry.
	(mips_issue_rate): Handle PROCESSOR_R5900.
	(mips_reorg_process_insns): Force reorder mode for the R5900.
	* config/mips/mips.h (TARGET_MIPS5900): Define.
	(ISA_HAS_CONDMOVE, ISA_HAS_PREFETCH, ISA_HAS_HILO_INTERLOCKS): Include
	TARGET_MIPS5900.
	(ISA_HAS_LOAD_DELAY, ISA_HAS_XFER_DELAY, ISA_HAS_FCMP_DELAY): Exclude
	TARGET_MIPS5900.
	* config/mips/mips.md (processor): Add r5900.
	(MOVECC): Disallow CCmode conditions for TARGET_MIPS5900.

libgcc/
2013-06-03  Jürgen Urban  <JuergenUrban@gmx.de>

	* config.host (mipsr5900-*-elf*, mipsr5900el-*-elf*, mips64r5900-*-elf*)
	(mips64r5900el-*-elf*): New configurations.

Basic support for MIPS r5900

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