intel/fs: New VGRF packing scheme for constant combining

intel/fs: New VGRF packing scheme for constant combining

Each block is processed separately.  VGRF channels that are allocated to
values that are only used in a particular block are made available in
other blocks.

This is almost always an improvement, but there are some pessimal cases
where it goes horribly wrong.  Imagine a shader with two blocks.  In
that shader, the first block has 5 constants used in the first block and
the second block.  Three other constants are only used in the first
block.  The second block has 15 constants that are used only in the
block.  The static VGRF usage is 3 regardless of packing.  However,
scheduling may be able to shorten the live range of the first VGRF when
it only has values that came from the first block (because three of the
values are dead on entry to the second block).

This used to occurs in a Mad Max shader on Broadwell.  That shader
went from 0:0 spills:fills to 107:52.  Some changes over the last
year, I'm assuming !13734, have prevented this case from occuring.

This change created a lot of churn on Haswell and Ivy Bridge.  This
seems to be primarily due to all the extra constants used for coissue,
but I did not investigate very deeply.  On older platforms, there were
no changes to spills or fills.  As a result, this is only used on
Broadwell and newer platforms.

v2: Update expected checksum for pixmark-piano-v2.trace on
gl-zink-anv-tgl. See #9714 for more details.

shader-db results:

Tiger Lake
total instructions in shared programs: 21101332 -> 21102084 (<.01%)
instructions in affected programs: 863686 -> 864438 (0.09%)
helped: 463 / HURT: 437

total cycles in shared programs: 790573225 -> 790664391 (0.01%)
cycles in affected programs: 92546803 -> 92637969 (0.10%)
helped: 558 / HURT: 629

total spills in shared programs: 3959 -> 3951 (-0.20%)
spills in affected programs: 184 -> 176 (-4.35%)
helped: 2 / HURT: 0

total fills in shared programs: 2639 -> 2631 (-0.30%)
fills in affected programs: 184 -> 176 (-4.35%)
helped: 2 / HURT: 0

LOST:   1
GAINED: 5

Ice Lake and Skylake had similar results. (Ice Lake shown)
total instructions in shared programs: 19945216 -> 19944711 (<.01%)
instructions in affected programs: 139569 -> 139064 (-0.36%)
helped: 66 / HURT: 3

total cycles in shared programs: 858410082 -> 857381323 (-0.12%)
cycles in affected programs: 383825958 -> 382797199 (-0.27%)
helped: 1012 / HURT: 1055

total spills in shared programs: 6190 -> 6116 (-1.20%)
spills in affected programs: 891 -> 817 (-8.31%)
helped: 66 / HURT: 3

total fills in shared programs: 7382 -> 7238 (-1.95%)
fills in affected programs: 1538 -> 1394 (-9.36%)
helped: 66 / HURT: 3

LOST:   5
GAINED: 8

Broadwell
total instructions in shared programs: 17820886 -> 17812515 (-0.05%)
instructions in affected programs: 800512 -> 792141 (-1.05%)
helped: 385 / HURT: 1

total cycles in shared programs: 904482935 -> 903102070 (-0.15%)
cycles in affected programs: 422427015 -> 421046150 (-0.33%)
helped: 1091 / HURT: 812

total spills in shared programs: 17908 -> 16576 (-7.44%)
spills in affected programs: 9459 -> 8127 (-14.08%)
helped: 386 / HURT: 0

total fills in shared programs: 25397 -> 22354 (-11.98%)
fills in affected programs: 15504 -> 12461 (-19.63%)
helped: 385 / HURT: 1

LOST:   2
GAINED: 2

No shader-db changes on Haswell or older platforms.

fossil-db results:

Tiger Lake
Instructions in all programs: 156881463 -> 156890970 (+0.0%)
Instructions helped: 9033
Instructions hurt: 10285

Cycles in all programs: 7532597466 -> 7529647924 (-0.0%)
Cycles helped: 10548
Cycles hurt: 13667

Spills in all programs: 5490 -> 5110 (-6.9%)
Spills helped: 100
Spills hurt: 3

Fills in all programs: 6123 -> 5752 (-6.1%)
Fills helped: 100
Fills hurt: 3

Gained: 17
Lost: 47

Ice Lake
Instructions in all programs: 141309644 -> 141309603 (-0.0%)
Instructions helped: 9
Instructions hurt: 4

Cycles in all programs: 9095812690 -> 9097008049 (+0.0%)
Cycles helped: 14288
Cycles hurt: 16381

Spills in all programs: 7418 -> 7404 (-0.2%)
Spills helped: 9
Spills hurt: 4

Fills in all programs: 8326 -> 8321 (-0.1%)
Fills helped: 9
Fills hurt: 4

Skylake
Instructions in all programs: 131872347 -> 131870690 (-0.0%)
Instructions helped: 111
Instructions hurt: 3

Cycles in all programs: 8800835649 -> 8802483884 (+0.0%)
Cycles helped: 9415
Cycles hurt: 9678

Spills in all programs: 6917 -> 6476 (-6.4%)
Spills helped: 111
Spills hurt: 3

Fills in all programs: 7584 -> 7354 (-3.0%)
Fills helped: 111
Fills hurt: 3

Lost: 5

Tested-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7698>