Re: [Mesa-dev] [PATCH v9 0/7] mesa/st: glsl_to_tgsi: refined register merge algorithm

[Nicolai Hähnle]

On 06.09.2017 17:00, Dieter Nützel wrote:

Am 06.09.2017 11:53, schrieb Nicolai Hähnle:

I finally went over this again, and I think it's good enough to go in.
R-b and pushed!

Thanks for making all the adjustments and your patience :)

I did notice some minor things, I'm about to send out patches to clean
things up afterwards.

Cheers,
Nicolai


Wow,

this IS GREAT news!
But you've lost all my T-b ... ;-)))


Sorry about that. I guess you didn't send them on the last version?

Gert, for the future, the usual policy is that when you receive 
Tested-by (or other things) on earlier versions of commits, you add them as


Tested-by: Firstname Lastname  (vNN)

where vNN is whichever version of the series you received the Tested-by 
for. That way, they won't get lost :)


Cheers,
Nicolai




What I've found and didn't mailed before is, that I see ~50 KB smaller 
size off the *dr[i|v].so files with Gert's nice stuff.


Thank you very much for this, Gert!

I'll swap my Turks XT/6670 back in and test LS2015 on it again, too 
verify if the missing textures (people) appear, now.


Greetings,
Dieter



On 24.08.2017 19:38, Gert Wollny wrote:

Dear all,

I thought I might send out this patch another time with its full 
history and
freshly rebased. All the changes that I applied were a result of 
reviews by

Nicolai (mostly) and Emil (thanks again to both of you).

The set is mirroed at
https://github.com/gerddie/mesa/tree/regrename-v9

The patch fixes a series of bugs where shader compilation fails with
   "translation from TGSI failed!"
Among these are
   * https://bugs.freedesktop.org/show_bug.cgi?id=65448 which
 I can confirm will be fixed for R600_DEBUG=nosb set (with sb 
enabled it will

 fail with a failing assertion in the sb code).
   * According to a user report against v5, the patch also fixes #99349

I can also confirm that the patch fixes the Piano and Voloplosion 
benchmarks

implemented in gputest on BARTS (r600g).

The patch has no significant impact on runtime - not taking Dave's 
patch into
account that in itself reduces the register renaming run-time for 
shaders

with a large numbers of temporary registers.

The patch doesn't introduce piglit regression (I tested the shader 
subset).
spec@glsl-1.50@execution@variable-indexing@gs-input-array-vec2-index-rd 
is

fixed though.

The algorithm works like follows:
- first the program is scanned, the loops, switch and if/else scopes are
   collected and for each temporary first and last reads and writes 
and the
   according scopes are collected, and it is recorded whether a 
variable is
   written conditionally, and whether loops have continue or break 
statements.
- then after the whole program has been scanned, the life times are 
estimated
   by merging the read and write scopes for each temporary on a per 
component

   bases,
- the life-times of the cmponents are merged,
- the register mapping is evaluated, and
- the mapping is applied with the rename_temp_registers method 
implemented

   by Dave.

I've used the patches for quite some time now and so far I didn't 
encounter

any problems, many thanks for any comments,
  Gert

Patch history:

v2:* significantly cut down on the memory allocations,
* expose only a minimal interface to register lifetime estimation 
and

  calculating the rename table,
v3: was broken and v4 restarted from v2

v4:* split the changes into more patches
* correct formatting errors,
* remove the use of the STL with one exception though:
  since in st_glsl_to_tgsi.cpp std::sort is already used and its 
run-time
  performance is significantly better than qsort. It is used in 
the register
  rename mapping evaluation. It can be disabled by commenting out 
the define

  USE_STL_SORT in st_glsl_to_tgsi_temprename.cpp.
* add more tests and improve the life-time evaluation accordingly,
* further reduce memory allocations,
* rename functions and methods to better clarify what they are 
used for,

* remove unused methods and variables in prog_scope,
* eliminate the class tgsi_temp_lifetime,
* no longer require C++11 for the core library code, however, the 
tests

  make use of C++11 and the STL

v5: * correct formatting following Emil's suggetions
 * remove un-needed libraries for the tests

v6:* the components are now tracked individually and the life time of 
a temporary

  is evaluated by merging the life-times of their components,
* BRK/CONT are now handled separately,
* the final algorithm to evaluate the life-times was simplified,
* read and write in the same instruction is now considered to be 
always

  well defined,
* adherence to the coding stile was improved,
* the case scope level is now below the according switch scope 
level,
* the new register merge method replaces the old version, i.e. no 
environment
  variables to switch between implementations. In theory, one 
could also
  remove 

Re: [Mesa-dev] [PATCH v9 0/7] mesa/st: glsl_to_tgsi: refined register merge algorithm

[Dieter Nützel]

Am 06.09.2017 11:53, schrieb Nicolai Hähnle:

I finally went over this again, and I think it's good enough to go in.
R-b and pushed!

Thanks for making all the adjustments and your patience :)

I did notice some minor things, I'm about to send out patches to clean
things up afterwards.

Cheers,
Nicolai


Wow,

this IS GREAT news!
But you've lost all my T-b ... ;-)))

What I've found and didn't mailed before is, that I see ~50 KB smaller 
size off the *dr[i|v].so files with Gert's nice stuff.


Thank you very much for this, Gert!

I'll swap my Turks XT/6670 back in and test LS2015 on it again, too 
verify if the missing textures (people) appear, now.


Greetings,
Dieter



On 24.08.2017 19:38, Gert Wollny wrote:

Dear all,

I thought I might send out this patch another time with its full 
history and
freshly rebased. All the changes that I applied were a result of 
reviews by

Nicolai (mostly) and Emil (thanks again to both of you).

The set is mirroed at
https://github.com/gerddie/mesa/tree/regrename-v9

The patch fixes a series of bugs where shader compilation fails with
   "translation from TGSI failed!"
Among these are
   * https://bugs.freedesktop.org/show_bug.cgi?id=65448 which
 I can confirm will be fixed for R600_DEBUG=nosb set (with sb 
enabled it will

 fail with a failing assertion in the sb code).
   * According to a user report against v5, the patch also fixes 
#99349


I can also confirm that the patch fixes the Piano and Voloplosion 
benchmarks

implemented in gputest on BARTS (r600g).

The patch has no significant impact on runtime - not taking Dave's 
patch into
account that in itself reduces the register renaming run-time for 
shaders

with a large numbers of temporary registers.

The patch doesn't introduce piglit regression (I tested the shader 
subset).
spec@glsl-1.50@execution@variable-indexing@gs-input-array-vec2-index-rd 
is

fixed though.

The algorithm works like follows:
- first the program is scanned, the loops, switch and if/else scopes 
are
   collected and for each temporary first and last reads and writes 
and the
   according scopes are collected, and it is recorded whether a 
variable is
   written conditionally, and whether loops have continue or break 
statements.
- then after the whole program has been scanned, the life times are 
estimated
   by merging the read and write scopes for each temporary on a per 
component

   bases,
- the life-times of the cmponents are merged,
- the register mapping is evaluated, and
- the mapping is applied with the rename_temp_registers method 
implemented

   by Dave.

I've used the patches for quite some time now and so far I didn't 
encounter

any problems, many thanks for any comments,
  Gert

Patch history:

v2:* significantly cut down on the memory allocations,
* expose only a minimal interface to register lifetime estimation 
and

  calculating the rename table,
v3: was broken and v4 restarted from v2

v4:* split the changes into more patches
* correct formatting errors,
* remove the use of the STL with one exception though:
  since in st_glsl_to_tgsi.cpp std::sort is already used and its 
run-time
  performance is significantly better than qsort. It is used in 
the register
  rename mapping evaluation. It can be disabled by commenting out 
the define

  USE_STL_SORT in st_glsl_to_tgsi_temprename.cpp.
* add more tests and improve the life-time evaluation accordingly,
* further reduce memory allocations,
* rename functions and methods to better clarify what they are 
used for,

* remove unused methods and variables in prog_scope,
* eliminate the class tgsi_temp_lifetime,
* no longer require C++11 for the core library code, however, the 
tests

  make use of C++11 and the STL

v5: * correct formatting following Emil's suggetions
 * remove un-needed libraries for the tests

v6:* the components are now tracked individually and the life time of 
a temporary

  is evaluated by merging the life-times of their components,
* BRK/CONT are now handled separately,
* the final algorithm to evaluate the life-times was simplified,
* read and write in the same instruction is now considered to be 
always

  well defined,
* adherence to the coding stile was improved,
* the case scope level is now below the according switch scope 
level,
* the new register merge method replaces the old version, i.e. no 
environment
  variables to switch between implementations. In theory, one 
could also
  remove the function get_last_temp_read_first_temp_write, but is 
is still

  used in some code in a #define 0 block, so I didn't touch it.
* when compiled in debug mode and with the environment variable
  GLSL_TO_TGSI_RENAME_DEBUG specified the TGSI and resulting 
register

  lifetimes will be dumped to stderr.Here Nicolai suggested to use
  _mesa_register_file_name instead of my hand-backed array of 
strings,
  but 

Re: [Mesa-dev] [PATCH v9 0/7] mesa/st: glsl_to_tgsi: refined register merge algorithm

[Gert Wollny]

Am Mittwoch, den 06.09.2017, 11:53 +0200 schrieb Nicolai Hähnle:
> I finally went over this again, and I think it's good enough to go
> in. R-b and pushed!
Thanks :) 

Unfortunately it fails to build on this AppVoyager scons build (MS
Windows?) 

The first failure I see is that it doesn't recognize 

numeric_limits::max() 

even though  is included and 

  using std::numeric_limits;

specified. 

The other problem is that it doesn't recognize "access_record", maybe
the compiler expects "struct" to be specified every time (like in C)?


> I did notice some minor things, I'm about to send out patches to
> clean things up afterwards.
I will test these patches ASAP. 

Best, 
Gert 


> 
> Cheers,
> Nicolai
> 
> 
> On 24.08.2017 19:38, Gert Wollny wrote:
> > Dear all,
> > 
> > I thought I might send out this patch another time with its full
> > history and
> > freshly rebased. All the changes that I applied were a result of
> > reviews by
> > Nicolai (mostly) and Emil (thanks again to both of you).
> > 
> > The set is mirroed at
> > https://github.com/gerddie/mesa/tree/regrename-v9
> > 
> > The patch fixes a series of bugs where shader compilation fails
> > with
> >    "translation from TGSI failed!"
> > Among these are
> >    * https://bugs.freedesktop.org/show_bug.cgi?id=65448 which
> >  I can confirm will be fixed for R600_DEBUG=nosb set (with sb
> > enabled it will
> >  fail with a failing assertion in the sb code).
> >    * According to a user report against v5, the patch also fixes
> > #99349
> > 
> > I can also confirm that the patch fixes the Piano and Voloplosion
> > benchmarks
> > implemented in gputest on BARTS (r600g).
> > 
> > The patch has no significant impact on runtime - not taking Dave's
> > patch into
> > account that in itself reduces the register renaming run-time for
> > shaders
> > with a large numbers of temporary registers.
> > 
> > The patch doesn't introduce piglit regression (I tested the shader
> > subset).
> > spec@glsl-1.50@execution@variable-indexing@gs-input-array-vec2-
> > index-rd is
> > fixed though.
> > 
> > The algorithm works like follows:
> > - first the program is scanned, the loops, switch and if/else
> > scopes are
> >    collected and for each temporary first and last reads and writes
> > and the
> >    according scopes are collected, and it is recorded whether a
> > variable is
> >    written conditionally, and whether loops have continue or break
> > statements.
> > - then after the whole program has been scanned, the life times are
> > estimated
> >    by merging the read and write scopes for each temporary on a per
> > component
> >    bases,
> > - the life-times of the cmponents are merged,
> > - the register mapping is evaluated, and
> > - the mapping is applied with the rename_temp_registers method
> > implemented
> >    by Dave.
> > 
> > I've used the patches for quite some time now and so far I didn't
> > encounter
> > any problems, many thanks for any comments,
> >   
> > Gert
> > 
> > Patch history:
> > 
> > v2:* significantly cut down on the memory allocations,
> > * expose only a minimal interface to register lifetime
> > estimation and
> >   calculating the rename table,
> > 
> > v3: was broken and v4 restarted from v2
> > 
> > v4:* split the changes into more patches
> > * correct formatting errors,
> > * remove the use of the STL with one exception though:
> >   since in st_glsl_to_tgsi.cpp std::sort is already used and
> > its run-time
> >   performance is significantly better than qsort. It is used in
> > the register
> >   rename mapping evaluation. It can be disabled by commenting
> > out the define
> >   USE_STL_SORT in st_glsl_to_tgsi_temprename.cpp.
> > * add more tests and improve the life-time evaluation
> > accordingly,
> > * further reduce memory allocations,
> > * rename functions and methods to better clarify what they are
> > used for,
> > * remove unused methods and variables in prog_scope,
> > * eliminate the class tgsi_temp_lifetime,
> > * no longer require C++11 for the core library code, however,
> > the tests
> >   make use of C++11 and the STL
> > 
> > v5: * correct formatting following Emil's suggetions
> >  * remove un-needed libraries for the tests
> > 
> > v6:* the components are now tracked individually and the life time
> > of a temporary
> >   is evaluated by merging the life-times of their components,
> > * BRK/CONT are now handled separately,
> > * the final algorithm to evaluate the life-times was
> > simplified,
> > * read and write in the same instruction is now considered to
> > be always
> >   well defined,
> > * adherence to the coding stile was improved,
> > * the case scope level is now below the according switch scope
> > level,
> > * the new register merge method replaces the old version, i.e.
> > no environment
> >   variables to switch between implementations. In theory, one
> > could also
> > 

Re: [Mesa-dev] [PATCH v9 0/7] mesa/st: glsl_to_tgsi: refined register merge algorithm

[Nicolai Hähnle]

I finally went over this again, and I think it's good enough to go in. 
R-b and pushed!


Thanks for making all the adjustments and your patience :)

I did notice some minor things, I'm about to send out patches to clean 
things up afterwards.


Cheers,
Nicolai


On 24.08.2017 19:38, Gert Wollny wrote:

Dear all,

I thought I might send out this patch another time with its full history and
freshly rebased. All the changes that I applied were a result of reviews by
Nicolai (mostly) and Emil (thanks again to both of you).

The set is mirroed at
https://github.com/gerddie/mesa/tree/regrename-v9

The patch fixes a series of bugs where shader compilation fails with
   "translation from TGSI failed!"
Among these are
   * https://bugs.freedesktop.org/show_bug.cgi?id=65448 which
 I can confirm will be fixed for R600_DEBUG=nosb set (with sb enabled it 
will
 fail with a failing assertion in the sb code).
   * According to a user report against v5, the patch also fixes #99349

I can also confirm that the patch fixes the Piano and Voloplosion benchmarks
implemented in gputest on BARTS (r600g).

The patch has no significant impact on runtime - not taking Dave's patch into
account that in itself reduces the register renaming run-time for shaders
with a large numbers of temporary registers.

The patch doesn't introduce piglit regression (I tested the shader subset).
spec@glsl-1.50@execution@variable-indexing@gs-input-array-vec2-index-rd is
fixed though.

The algorithm works like follows:
- first the program is scanned, the loops, switch and if/else scopes are
   collected and for each temporary first and last reads and writes and the
   according scopes are collected, and it is recorded whether a variable is
   written conditionally, and whether loops have continue or break statements.
- then after the whole program has been scanned, the life times are estimated
   by merging the read and write scopes for each temporary on a per component
   bases,
- the life-times of the cmponents are merged,
- the register mapping is evaluated, and
- the mapping is applied with the rename_temp_registers method implemented
   by Dave.

I've used the patches for quite some time now and so far I didn't encounter
any problems, many thanks for any comments,
  
Gert


Patch history:

v2:* significantly cut down on the memory allocations,
* expose only a minimal interface to register lifetime estimation and
  calculating the rename table,

v3: was broken and v4 restarted from v2


v4:* split the changes into more patches
* correct formatting errors,
* remove the use of the STL with one exception though:
  since in st_glsl_to_tgsi.cpp std::sort is already used and its run-time
  performance is significantly better than qsort. It is used in the register
  rename mapping evaluation. It can be disabled by commenting out the define
  USE_STL_SORT in st_glsl_to_tgsi_temprename.cpp.
* add more tests and improve the life-time evaluation accordingly,
* further reduce memory allocations,
* rename functions and methods to better clarify what they are used for,
* remove unused methods and variables in prog_scope,
* eliminate the class tgsi_temp_lifetime,
* no longer require C++11 for the core library code, however, the tests
  make use of C++11 and the STL

v5: * correct formatting following Emil's suggetions
 * remove un-needed libraries for the tests

v6:* the components are now tracked individually and the life time of a 
temporary
  is evaluated by merging the life-times of their components,
* BRK/CONT are now handled separately,
* the final algorithm to evaluate the life-times was simplified,
* read and write in the same instruction is now considered to be always
  well defined,
* adherence to the coding stile was improved,
* the case scope level is now below the according switch scope level,
* the new register merge method replaces the old version, i.e. no 
environment
  variables to switch between implementations. In theory, one could also
  remove the function get_last_temp_read_first_temp_write, but is is still
  used in some code in a #define 0 block, so I didn't touch it.
* when compiled in debug mode and with the environment variable
  GLSL_TO_TGSI_RENAME_DEBUG specified the TGSI and resulting register
  lifetimes will be dumped to stderr.Here Nicolai suggested to use
  _mesa_register_file_name instead of my hand-backed array of strings,
  but currently that function doesn't write out all the needed names,
  so I thought it might be better to address this in another patch that
  also extends _mesa_register_file_name,
* unused registers are now ignored in the rename mapping evaluation,
* registers that are only read get a life-time {x,x}, with x the instruction
  line were the register is last read, so they can be merged,
* the patch has been rebased against 7d7bcd65d

v7:* 

Re: [Mesa-dev] [PATCH v9 0/7] mesa/st: glsl_to_tgsi: refined register merge algorithm

[Michel Dänzer]

On 25/08/17 05:30 PM, Gert Wollny wrote:
> Am Freitag, den 25.08.2017, 10:20 +0900 schrieb Michel Dänzer:
>> On 25/08/17 02:38 AM, Gert Wollny wrote:
>>>
>>> The patch doesn't introduce piglit regression (I tested the shader
>>> subset). 
>>
>> I'd recommend testing at least the gpu profile, ideally running on X.
> 
> I've done that now running the gpu profile with clean upstream
> (f623e1742f) and my patches on top (twice each time). The only
> consistent change is fixing  
> 
>vs-output-array-vec2-index-wr-before-gs 
> 
> A bit strange is spec/arb_sync/repeate_wait because it is skipped once
> with clean upstream but passes otherwise.
> 
> spec/nv_conditional_render failed once with my patch applied, but it
> doesn't do any register merging and when I run the test from the
> command line it always passes (also when explicitly cleaning the shader
> cache). I didn't try running it with a clean upstream more then twice
> though. 
> 
> All other changes versus a clean upstream are non-deterministic, i.e.
> fail and pass once for each code version. 
> 
> In detail these are 
> 
> glx/
>   - glx_arb_sync_control (all timing-* tests)
> 
>   - security
>   initialized-fbo   (warn/pass)
>   initialized-texmemory (warn/pass), 
> 
> spec/
>   - arb_tessellation_shader
>  tcs-input-read-array-interface
>  tcs-input-read-mat
>  tcs-input-read-nonconst-interface-builtin

Looks fine, thanks. Most of these tests are known to give non-stable
results with radeonsi as well.


-- 
Earthling Michel Dänzer   |   http://www.amd.com
Libre software enthusiast | Mesa and X developer
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Re: [Mesa-dev] [PATCH v9 0/7] mesa/st: glsl_to_tgsi: refined register merge algorithm

[Gert Wollny]

Am Freitag, den 25.08.2017, 10:20 +0900 schrieb Michel Dänzer:
> On 25/08/17 02:38 AM, Gert Wollny wrote:
> > 
> > The patch doesn't introduce piglit regression (I tested the shader
> > subset). 
> 
> I'd recommend testing at least the gpu profile, ideally running on X.

I've done that now running the gpu profile with clean upstream
(f623e1742f) and my patches on top (twice each time). The only
consistent change is fixing  

   vs-output-array-vec2-index-wr-before-gs 

A bit strange is spec/arb_sync/repeate_wait because it is skipped once
with clean upstream but passes otherwise.

spec/nv_conditional_render failed once with my patch applied, but it
doesn't do any register merging and when I run the test from the
command line it always passes (also when explicitly cleaning the shader
cache). I didn't try running it with a clean upstream more then twice
though. 

All other changes versus a clean upstream are non-deterministic, i.e.
fail and pass once for each code version. 

In detail these are 

glx/
  - glx_arb_sync_control (all timing-* tests)

  - security
  initialized-fbo   (warn/pass)
  initialized-texmemory (warn/pass), 

spec/
  - arb_tessellation_shader
     tcs-input-read-array-interface
     tcs-input-read-mat
     tcs-input-read-nonconst-interface-builtin

Best, 
Gert 


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Re: [Mesa-dev] [PATCH v9 0/7] mesa/st: glsl_to_tgsi: refined register merge algorithm

[Michel Dänzer]

On 25/08/17 02:38 AM, Gert Wollny wrote:
> 
> The patch doesn't introduce piglit regression (I tested the shader subset). 

I'd recommend testing at least the gpu profile, ideally running on X.


-- 
Earthling Michel Dänzer   |   http://www.amd.com
Libre software enthusiast | Mesa and X developer
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[Mesa-dev] [PATCH v9 0/7] mesa/st: glsl_to_tgsi: refined register merge algorithm

[Gert Wollny]

Dear all, 

I thought I might send out this patch another time with its full history and 
freshly rebased. All the changes that I applied were a result of reviews by 
Nicolai (mostly) and Emil (thanks again to both of you).  

The set is mirroed at 
   https://github.com/gerddie/mesa/tree/regrename-v9

The patch fixes a series of bugs where shader compilation fails with 
  "translation from TGSI failed!" 
Among these are 
  * https://bugs.freedesktop.org/show_bug.cgi?id=65448 which 
I can confirm will be fixed for R600_DEBUG=nosb set (with sb enabled it 
will 
fail with a failing assertion in the sb code).
  * According to a user report against v5, the patch also fixes #99349

I can also confirm that the patch fixes the Piano and Voloplosion benchmarks 
implemented in gputest on BARTS (r600g).

The patch has no significant impact on runtime - not taking Dave's patch into
account that in itself reduces the register renaming run-time for shaders 
with a large numbers of temporary registers.  

The patch doesn't introduce piglit regression (I tested the shader subset). 
spec@glsl-1.50@execution@variable-indexing@gs-input-array-vec2-index-rd is 
fixed though. 

The algorithm works like follows:
- first the program is scanned, the loops, switch and if/else scopes are 
  collected and for each temporary first and last reads and writes and the 
  according scopes are collected, and it is recorded whether a variable is 
  written conditionally, and whether loops have continue or break statements.
- then after the whole program has been scanned, the life times are estimated 
  by merging the read and write scopes for each temporary on a per component 
  bases, 
- the life-times of the cmponents are merged, 
- the register mapping is evaluated, and  
- the mapping is applied with the rename_temp_registers method implemented 
  by Dave. 

I've used the patches for quite some time now and so far I didn't encounter
any problems, many thanks for any comments, 
 
Gert

Patch history: 

v2:* significantly cut down on the memory allocations, 
   * expose only a minimal interface to register lifetime estimation and
 calculating the rename table,
   
v3: was broken and v4 restarted from v2 

v4:* split the changes into more patches 
   * correct formatting errors,
   * remove the use of the STL with one exception though: 
 since in st_glsl_to_tgsi.cpp std::sort is already used and its run-time 
 performance is significantly better than qsort. It is used in the register 
 rename mapping evaluation. It can be disabled by commenting out the define 
 USE_STL_SORT in st_glsl_to_tgsi_temprename.cpp. 
   * add more tests and improve the life-time evaluation accordingly,
   * further reduce memory allocations,
   * rename functions and methods to better clarify what they are used for,
   * remove unused methods and variables in prog_scope,
   * eliminate the class tgsi_temp_lifetime,
   * no longer require C++11 for the core library code, however, the tests 
 make use of C++11 and the STL

v5: * correct formatting following Emil's suggetions
* remove un-needed libraries for the tests

v6:* the components are now tracked individually and the life time of a 
temporary 
 is evaluated by merging the life-times of their components, 
   * BRK/CONT are now handled separately, 
   * the final algorithm to evaluate the life-times was simplified, 
   * read and write in the same instruction is now considered to be always 
 well defined,
   * adherence to the coding stile was improved, 
   * the case scope level is now below the according switch scope level, 
   * the new register merge method replaces the old version, i.e. no 
environment 
 variables to switch between implementations. In theory, one could also 
 remove the function get_last_temp_read_first_temp_write, but is is still 
 used in some code in a #define 0 block, so I didn't touch it.  
   * when compiled in debug mode and with the environment variable 
 GLSL_TO_TGSI_RENAME_DEBUG specified the TGSI and resulting register 
 lifetimes will be dumped to stderr.Here Nicolai suggested to use 
 _mesa_register_file_name instead of my hand-backed array of strings, 
 but currently that function doesn't write out all the needed names, 
 so I thought it might be better to address this in another patch that 
 also extends _mesa_register_file_name, 
   * unused registers are now ignored in the rename mapping evaluation, 
   * registers that are only read get a life-time {x,x}, with x the instruction 
 line were the register is last read, so they can be merged,
   * the patch has been rebased against 7d7bcd65d

v7:* Correct documentation of GLSL_TO_TGSI_RENAME_DEBUG in commit message.  
   * fix typos, include files, formatting, and some variable names,
   * add anonymous namespace around classes, 
   * replace debug_log singleton by a function,
   * cleanup the switch-case scope creation, 
   * track switch