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aco/spill: avoid re-spilling loop-carried variables in process_block()

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If a variable is spilled at the loop-header of the current loop,
there is no need to spill it redundantly. Instead, re-use the
spill-slot from the loop-header.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27774>
This commit is contained in:
Daniel Schürmann 2024-02-21 16:48:18 +01:00 • committed by Marge Bot
parent bb3b6a5ff3
commit 7726b92707
1 changed files with 27 additions and 7 deletions
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34
src/amd/compiler/aco_spill.cpp
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@ -1157,25 +1157,45 @@ process_block(spill_ctx& ctx, unsigned block_idx, Block* block, RegisterDemand s
while ((new_demand - spilled_registers).exceeds(ctx.target_pressure)) {
unsigned distance = 0;
Temp to_spill;
bool do_rematerialize = false;
unsigned do_rematerialize = 0;
unsigned avoid_respill = 0;
RegType type = RegType::sgpr;
if (new_demand.vgpr - spilled_registers.vgpr > ctx.target_pressure.vgpr)
type = RegType::vgpr;
for (std::pair<Temp, uint32_t> pair : ctx.local_next_use_distance[idx]) {
if (pair.first.type() != type)
if (pair.first.type() != type || current_spills.count(pair.first))
continue;
bool can_rematerialize = ctx.remat.count(pair.first);
if (((pair.second > distance && can_rematerialize == do_rematerialize) ||
(can_rematerialize && !do_rematerialize && pair.second > idx)) &&
!current_spills.count(pair.first)) {
unsigned can_rematerialize = ctx.remat.count(pair.first);
unsigned loop_variable =
block->loop_nest_depth && ctx.loop.back().spills.count(pair.first);
if (avoid_respill > loop_variable || do_rematerialize > can_rematerialize)
continue;
if (can_rematerialize > do_rematerialize || loop_variable > avoid_respill ||
pair.second > distance) {
/* Don't spill operands */
if (pair.second <= idx)
continue;
to_spill = pair.first;
distance = pair.second;
do_rematerialize = can_rematerialize;
avoid_respill = loop_variable;
}
}
assert(distance != 0 && distance > idx);
if (avoid_respill) {
/* This variable is spilled at the loop-header of the current loop.
* Re-use the spill-slot in order to avoid an extra store.
*/
current_spills[to_spill] = ctx.loop.back().spills[to_spill];
spilled_registers += to_spill;
continue;
}
uint32_t spill_id = ctx.add_to_spills(to_spill, current_spills);
/* add interferences with reloads */
for (std::pair<const Temp, std::pair<Temp, uint32_t>>& pair : reloads)