Save the next person from digging through the code to figure out what
the indirect_mask parameter actually does.
Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
When an if nesting inside anouther if is optimised away we can
end up with a loop terminator and following block that looks like
this:
if ssa_596 {
block block_5:
/* preds: block_4 */
vec1 32 ssa_601 = load_const (0xffffffff /* -nan */)
break
/* succs: block_8 */
} else {
block block_6:
/* preds: block_4 */
/* succs: block_7 */
}
block block_7:
/* preds: block_6 */
vec1 32 ssa_602 = phi block_6: ssa_552
vec1 32 ssa_603 = phi block_6: ssa_553
vec1 32 ssa_604 = iadd ssa_551, ssa_66
The problem is the phis. Loop unrolling expects the last block in
the loop to be empty once we splice the instructions in the last
block into the continue branch. The problem is we cant move phis
so here we lower the phis to regs when preparing the loop for
unrolling. As it could be possible to have multiple additional
blocks/ifs following the terminator we just convert all phis at
the top level of the loop body for simplicity.
We also add some comments to loop_prepare_for_unroll() while we
are here.
Fixes: 51daccb289 "nir: add a loop unrolling pass"
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105670
This reverts commit 2d36efdb7f.
This raised limit turns out to harmful for more complex shaders,
it causes excessive spilling in some Bioshock Infinite shaders.
The fps for the ssao demo on radv remains unchanged when reverting
this.
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
With the ssao demo from Vulkan demos:
radv/rx480: 440->440fps
anv/haswell: 24->34 fps
The demo does a 0->32 loop across a ubo with 32 members.
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
The original number was chosen in an attempt to match the limits applied to
GLSL IR.
A look at the git history of the why these limits were chosen for GLSL IR
shows it was more to do with the slow speed of unrolling large loops in
GLSL IR than anything else. The speed of loop unrolling in NIR is not a
problem so we may wish to bump this even higher in future.
No shader-db change, however a furture change will disbale the GLSL IR
optimisation loop in the i965 backend results in 4 loops from The Talos
Principle failing to unroll. Bumping the limit allows them to unroll which
results in the instruction count matching the previous output from when the
GLSL IR opts were still enabled.
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
V2:
- tidy ups suggested by Connor.
- tidy up cloning logic and handle copy propagation
based of suggestion by Connor.
- use nir_ssa_def_rewrite_uses to fix up lcssa phis
suggested by Connor.
- add support for complex loop unrolling (two terminators)
- handle case were the ssa defs use outside the loop is already a phi
- support unrolling loops with multiple terminators when trip count
is know for each terminator
V3:
- set correct num_components when creating phi in complex unroll
- rewrite update remap table based on Jasons suggestions.
- remove unrequired extract_loop_body() helper as suggested by Jason.
- simplify the lcssa phi fix up code for simple loops as per Jasons suggestions.
- use mem context to keep track of hash table memory as suggested by Jason.
- move is_{complex,simple}_loop helpers to the unroll code
- require nir_metadata_block_index
- partially rewrote complex unroll to be simpler and easier to follow.
V4:
- use rzalloc() when creating nir_phi_src but not setting pred right away
fixes regression cause by ralloc() no longer zeroing memory.
V5:
- simplify calling of complex_unroll()
- use new loop terminator fields to get the break/continue from blocks
and simplify loop unrolling code
- handle slightly less trivial loop terminators. if branches can
now have instructions but can only contain a single block.
- use nir print type IR snippets in unroll function descriptions
- add better explanation and variable for why we need to clone
additional times when the second terminator it the limiting
terminator.
- partially convert out of ssa before unrolling loops (suggested by Jason)
v6:
- remove unused nir_builder
- use Jasons new from ssa helper
- tidy/fixup cursor use
- unroll terminators that contain control flow correctly
- unroll complex loops with control flow before the terminators
correctly
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Rob Clark
Timothy Arceri
Dave Airlie
Elie TOURNIER
Timothy Arceri
Jason Ekstrand