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6 commits

Author SHA1 Message Date
Ian Romanick
33ad2bab4b nir/range-analysis: Adjust result range of exp2 to account for flush-to-zero
Fixes piglit tests (new in piglit!110):

    - fs-underflow-exp2-compare-zero.shader_test

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111308
Fixes: 405de7ccb6 ("nir/range-analysis: Rudimentary value range analysis pass")
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

Most of the shaders affected are, unsurprisingly, in Unigine Heaven.

All Gen6+ platforms had similar results. (Ice Lake shown)
total instructions in shared programs: 16278207 -> 16278465 (<.01%)
instructions in affected programs: 11374 -> 11632 (2.27%)
helped: 0
HURT: 58
HURT stats (abs)   min: 2 max: 13 x̄: 4.45 x̃: 4
HURT stats (rel)   min: 0.54% max: 4.11% x̄: 2.42% x̃: 2.82%
95% mean confidence interval for instructions value: 3.77 5.13
95% mean confidence interval for instructions %-change: 2.19% 2.64%
Instructions are HURT.

total cycles in shared programs: 367134284 -> 367135159 (<.01%)
cycles in affected programs: 81207 -> 82082 (1.08%)
helped: 17
HURT: 36
helped stats (abs) min: 6 max: 356 x̄: 90.35 x̃: 6
helped stats (rel) min: 0.69% max: 21.45% x̄: 5.71% x̃: 0.78%
HURT stats (abs)   min: 4 max: 235 x̄: 66.97 x̃: 16
HURT stats (rel)   min: 0.35% max: 27.58% x̄: 5.34% x̃: 1.09%
95% mean confidence interval for cycles value: -20.36 53.38
95% mean confidence interval for cycles %-change: -1.08% 4.67%
Inconclusive result (value mean confidence interval includes 0).

No changes on any earlier platforms.
2019-08-29 13:15:53 -07:00
Ian Romanick
f2965fde9b nir/range-analysis: Fail gracefully on non-SSA sources
Tested-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
2019-08-14 09:02:38 -07:00
Ian Romanick
fa116ce357 nir/range-analysis: Range tracking for ffma and flrp
A similar technique could be used for fmin3, fmax3, and fmid3.

This could be squashed with the previous commit.  I kept it separate to
ease review.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
2019-08-05 20:14:13 -07:00
Ian Romanick
586602c5d9 nir/range-analysis: Range tracking for bcsel
This could be squashed with the previous commit.  I kept it separate to
ease review.

v2: Add some missing cases.  Use nir_src_is_const helper.  Both
suggested by Caio.  Use a table for mapping source ranges to a result
range.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
2019-08-05 20:14:13 -07:00
Ian Romanick
3009cbed50 nir/range-analysis: Tighten the range of fsat based on the range of its source
This could be squashed with the previous commit.  I kept it separate to
ease review.

v2: Use a switch statement and add more comments.  Both suggested by
Caio.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
2019-08-05 20:14:13 -07:00
Ian Romanick
405de7ccb6 nir/range-analysis: Rudimentary value range analysis pass
Most integer operations are omitted because dealing with integer
overflow is hard.  There are a few things that could be smarter if there
was a small amount more tracking of ranges of integer types (i.e.,
operands are Boolean, operand values fit in 16 bits, etc.).

The changes to nir_search_helpers.h are included in this patch to
simplify reordering the changes to nir_opt_algebraic.py.

v2: Memoize range analysis results.  Without this, some shaders appear
to get stuck in infinite loops.

v3: Rebase on many months of Mesa changes, including 1-bit Boolean
changes.

v4: Rebase on "nir: Drop imov/fmov in favor of one mov instruction".

v5: Use nir_alu_srcs_equal for detecting (a*a).  Previously just the SSA
value was compared, and this incorrectly matched (a.x*a.y).

v6: Many code improvements including (but not limited to) better names,
more comments, and better use of helper functions.  All suggested by
Caio.  Rework the handling of several opcodes to use a table for mapping
source ranges to a result range.  This change fixed a bug that caused
fmax(gt_zero, ge_zero) to be incorrectly recognized as ge_zero.
Slightly tighten the range of fmul by recognizing that x*x is gt_zero if
x is gt_zero.  Add similar handling for -x*x.

v7: Use _______ in the tables as an alias for unknown.  Suggested by
Caio.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
2019-08-05 20:14:13 -07:00