Subzero, MIPS32: Fix FP register table

Subzero, MIPS32: Fix FP register table

FP register table did not contain correct register information.

R=stichnot@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=bf19533e91ca8d88f0bbca1376789f4c9de45da9

[obucinac, 2016-06-22 14:09:29]

Description was changed from

==========
Subzero, MIPS32: Fix FP register table

FP register table did not contain correct register information.
==========

to

==========
Subzero, MIPS32: Fix FP register table

FP register table did not contain correct register information.
==========

[obucinac, 2016-06-22 14:09:30]

obucinac@gmail.com changed reviewers:
+ mohit.bhakkad@imgtec.com, sagar.thakur@imgtec.com, stichnot@chromium.org

[Jim Stichnoth, 2016-06-22 15:48:49]

https://codereview.chromium.org/2089043003/diff/1/src/IceInstMIPS32.def
File src/IceInstMIPS32.def (right):

https://codereview.chromium.org/2089043003/diff/1/src/IceInstMIPS32.def#newco...
src/IceInstMIPS32.def:114: X(Reg_F0,       0,   "f0",    0,0,0,0, 0,0,1,0,0,    
                       \
I don't think this is right.

This cluster of 4 values is: scratch,preserved,stackptr,frameptr.

Almost every register should be marked as either scratch or preserved. 
Exceptions would be special registers like program counter, stack pointer, zero
register; and these would be marked scratch=0 preserved=0.

The ones marked as preserved will be automatically saved/restored in the
prolog/epilog if they are used.

The ones marked as scratch will be automatically killed across a function call.

[obucinac, 2016-06-22 16:28:33]

https://codereview.chromium.org/2089043003/diff/1/src/IceInstMIPS32.def
File src/IceInstMIPS32.def (right):

https://codereview.chromium.org/2089043003/diff/1/src/IceInstMIPS32.def#newco...
src/IceInstMIPS32.def:114: X(Reg_F0,       0,   "f0",    0,0,0,0, 0,0,1,0,0,    
                       \
On 2016/06/22 15:48:49, stichnot wrote:
> I don't think this is right.
> 
> This cluster of 4 values is: scratch,preserved,stackptr,frameptr.
> 
> Almost every register should be marked as either scratch or preserved. 
> Exceptions would be special registers like program counter, stack pointer,
zero
> register; and these would be marked scratch=0 preserved=0.
> 
> The ones marked as preserved will be automatically saved/restored in the
> prolog/epilog if they are used.
> 
> The ones marked as scratch will be automatically killed across a function
call.


f0-f3 are used for function return values.

f12-f15 are used for passing function arguments.

Looking at the GP register table, GP registers with these purposes are marked as
scratch, so I did the same...

[Jim Stichnoth, 2016-06-25 15:18:46]

lgtm

https://codereview.chromium.org/2089043003/diff/1/src/IceInstMIPS32.def
File src/IceInstMIPS32.def (right):

https://codereview.chromium.org/2089043003/diff/1/src/IceInstMIPS32.def#newco...
src/IceInstMIPS32.def:114: X(Reg_F0,       0,   "f0",    0,0,0,0, 0,0,1,0,0,    
                       \
On 2016/06/22 16:28:33, obucinac wrote:
> On 2016/06/22 15:48:49, stichnot wrote:
> > I don't think this is right.
> > 
> > This cluster of 4 values is: scratch,preserved,stackptr,frameptr.
> > 
> > Almost every register should be marked as either scratch or preserved. 
> > Exceptions would be special registers like program counter, stack pointer,
> zero
> > register; and these would be marked scratch=0 preserved=0.
> > 
> > The ones marked as preserved will be automatically saved/restored in the
> > prolog/epilog if they are used.
> > 
> > The ones marked as scratch will be automatically killed across a function
> call.
> 
> 
> f0-f3 are used for function return values.
> 
> f12-f15 are used for passing function arguments.
> 
> Looking at the GP register table, GP registers with these purposes are marked
as
> scratch, so I did the same...

OK, looks good.

FYI, if for some reason you want whose function arg/return registers to only be
used for arg/return purposes, and not as scratch registers available to the
register allocator, you can mark "0" in all the isInt/isFP/isVec columns.  The
register allocator will then respect all explicitly named uses of those
registers, but not use them otherwise.

[Jim Stichnoth, 2016-06-25 15:19:18]

Description was changed from

==========
Subzero, MIPS32: Fix FP register table

FP register table did not contain correct register information.
==========

to

==========
Subzero, MIPS32: Fix FP register table

FP register table did not contain correct register information.

R=stichnot@chromium.org

Committed:
https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a...
==========

[Jim Stichnoth, 2016-06-25 15:19:20]

Committed patchset #2 (id:20001) manually as
bf19533e91ca8d88f0bbca1376789f4c9de45da9 (presubmit successful).