These reverse the order of the comparison (e.g., -2 >= i vs i >= -2). I
split this into a separate commit because the previous commit was so
large.
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3445>
Loop analysis doesn't currently treat values updated by shifts as
induction variables. Future patches will change this.
v2: Don't use the contradiction ilt(x, INT_MIN).
v3: Delete some errant code in UNKNOWN_COUNT_TEST. Noticed by Tim.
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3445>
These track the same information in a slightly different way. Since
nir_loop_variable::init_src is visible outside this module, it cannot
be eliminated.
As an intentional side effect, induction variables with constant
initializers will now have their nir_loop_induction_variable::init_src
field point to the load_const source. Previously this pointer would be
NULL.
v2: Update unit tests and commit message. Remove the now unused ind_var
variable in find_trip_count.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21289>
As an intentional side effect, induction variables with constant
increments will now have their nir_loop_induction_variable::update_src
field point to the load_const source. Previously this pointer would be
NULL.
v2: Update unit tests and commit message.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21289>
A couple basic tests for loops with the exit condition after the
increment. In compiler literature, the optimization that moves the exit
condition from the top to the bottom is called "loop inversion."
v2: Pass parameters to loop_builder_invert using a struct. Add a comment
describing the loop being constructed to loop_builder_invert. Both
suggested by Caio.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21289>
Inspired heavily by the work by Yevhenii Kolesnikov in the original
versions of !3445.
v2: Pass parameters to loop_builder using a struct. Add a comment
describing the loop being constructed to loop_builder. Both suggested by
Caio.
v3: mscv C++ designated initializer lolz.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21289>
Consider the loop:
float i = 0.0;
while (true) {
if (i != 0.0)
break;
i = i + 1.0;
}
This loop clearly executes exactly one time.
Some trickery is necessary to handle cases where the initial loop value
is very large and the increment is, by comparison, very small. From the
fenu_once test case,
float i = -604462909807314587353088.0;
while (true) {
if (i != -604462909807314587353088.0)
break;
i = i + 36028797018963968.0;
}
This loop should also execute exactly once, but this is much more
challenging to calculate due to precision issues.
Going towards smaller magnitude (i.e., adding a small positive value to
a large negative value) requires a smaller delta to make a difference
than going towards a larger magnitude. For this reason,
-604462909807314587353088.0 + 36028797018963968.0 !=
-604462909807314587353088.0, but -604462909807314587353088.0 +
-36028797018963968.0 == -604462909807314587353088.0. Math class is
tough.
No changes in shader-db or fossil-db.
v2: Fix major bug in checking result of the eval_const_binop(nir_op_feq,
...) discovered while developing fneu_once_easy unit test. Fix a typo in
the comment just above that. Add fneu_once_easy test.
v3: Skip the iteration count adjustment tests for nir_op_fenu and
nir_op_ine. Since the iteration count is either 1 or unknown, all this
function can do is add numerical error. Add fenu_once tests.
v4: Change the initial value in the fneu_once test from large positive
to large negative. Change check in get_iteration from nir_op_fsub to
nir_op_fadd. Both changes from discussion with M Henning. Also add some
more explanation in fneu_once.
v5: Rename test cases.
Fixes: 6772a17acc ("nir: Add a loop analysis pass")
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19732>
I discovered this problem because adding an algebraic transformation to
convert some uge and ult to ieq or ine caused a couple loops to stop
unrolling. Consider the loop:
uint i = 0;
while (true) {
if (i >= 1)
break;
i++;
}
This loop clearly executes exactly one time. Note that uge(x, 1) is
equivalent to ine(x, 0). Changing the condition to 'if (i != 0)' will
also execute exactly one time.
In the added test cases, uge_once correctly get an exact loop trip count
of 1. Without the changes to nir_loop_analyze.c, the ine_once case
detects a maximum loop trip count of zero and does not get an exact loop
trip count.
No changes in shader-db or fossil-db.
v2: Move nir_op_fneu changes to a separate commit.
v3: Rename test cases.
Fixes: 6772a17acc ("nir: Add a loop analysis pass")
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19732>
This test comes from a comment in the loop analysis code.
The ine_zero test checks that zero iteration loops involving ine are
correctly identified.
v2: Add ine_zero test. Suggested by Tim.
v3: Rename test cases.
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19732>
