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nir: consider loop invariance in nir_src_is_divergent()

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By doing so, this function does not require LCSSA form anymore
in order to provide correct results.

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30787>
This commit is contained in:
Daniel Schürmann 2024-09-03 13:00:14 +02:00 • committed by Marge Bot
parent 1a55d6c23b
commit d34d2f8fa8
1 changed files with 34 additions and 1 deletions
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35
src/compiler/nir/nir_divergence_analysis.c
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@ -73,7 +73,40 @@ visit_cf_list(struct exec_list *list, struct divergence_state *state);
bool
nir_src_is_divergent(nir_src *src)
{
return src->ssa->divergent;
if (src->ssa->divergent)
return true;
nir_cf_node *use_node = nir_src_get_block(src)->cf_node.parent;
nir_cf_node *def_node = src->ssa->parent_instr->block->cf_node.parent;
/* Short-cut the common case. */
if (def_node == use_node)
return false;
/* If the source was computed in a divergent loop, and is not
* loop-invariant, then it must also be considered divergent.
*/
bool loop_invariant = src->ssa->loop_invariant;
while (def_node) {
if (def_node->type == nir_cf_node_loop) {
/* Check whether the use is inside this loop. */
for (nir_cf_node *node = use_node; node != NULL; node = node->parent) {
if (def_node == node)
return false;
}
/* Because the use is outside of this loop, it is divergent. */
if (nir_cf_node_as_loop(def_node)->divergent_break && !loop_invariant)
return true;
/* For outer loops, consider this variable not loop invariant. */
loop_invariant = false;
}
def_node = def_node->parent;
}
return false;
}
static inline bool