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nir/opt_loop: always try to peel initial break from loops with unrolling hint
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This allows to unroll these loops, even if loop analyze is unable
to calculate the iteration count.
As always with loops, the throughput stats are meaningless.

Totals from 6 (0.00% of 202440) affected shaders: (Navi48)
Instrs: 7825 -> 6201 (-20.75%)
CodeSize: 37056 -> 30412 (-17.93%)
Latency: 21563 -> 16934 (-21.47%)
InvThroughput: 144649 -> 77962 (-46.10%)
SClause: 139 -> 133 (-4.32%)
Copies: 536 -> 388 (-27.61%)
Branches: 156 -> 84 (-46.15%)
PreVGPRs: 298 -> 296 (-0.67%); split: -1.01%, +0.34%
VALU: 2493 -> 2378 (-4.61%); split: -4.65%, +0.04%
SALU: 3263 -> 2199 (-32.61%)
SMEM: 188 -> 183 (-2.66%)

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40349>
This commit is contained in:
Daniel Schürmann 2026-03-05 21:05:33 +01:00 • committed by Marge Bot
parent 738cc6a7db
commit 806fcc6193
1 changed files with 7 additions and 0 deletions
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7
src/compiler/nir/nir_opt_loop.c
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@ -356,6 +356,13 @@ should_peel_initial_break(nir_loop *loop)
nir_cf_node *if_node = nir_cf_node_next(&header_block->cf_node);
nir_if *nif = nir_cf_node_as_if(if_node);
/* If this loop is supposed to get unrolled, try doing so by peeling
* one iteration at a time. This works in cases where loop analysis
* is not able to calculate the iteration count.
*/
if (loop->control & nir_loop_control_unroll)
return can_constant_fold(nir_get_scalar(nif->condition.ssa, 0), header_block);
/* This loop is already in do-while form. */
if (loop->do_while)
return false;