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aco/gfx11: fix VMEM/DS->VALU WaW/RaW hazard

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Previously, we could safely read/write unused lanes of VMEM/DS
destination VGPRs without waiting for the load to finish. That doesn't
seem to be the case on GFX11.

fossil-db (gfx1100):
Totals from 6698 (4.94% of 135636) affected shaders:
Instrs: 11184274 -> 11199420 (+0.14%); split: -0.00%, +0.14%
CodeSize: 57578344 -> 57638928 (+0.11%); split: -0.00%, +0.11%
Latency: 198348808 -> 198382472 (+0.02%); split: -0.00%, +0.02%
InvThroughput: 24376324 -> 24378439 (+0.01%); split: -0.00%, +0.01%
VClause: 192420 -> 192559 (+0.07%)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/8722
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/8239
Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22965>
This commit is contained in:
Rhys Perry 2023-05-11 17:08:39 +01:00 • committed by Marge Bot
parent 8fc5dd935f
commit 88f6d7f4bd
2 changed files with 18 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
src/amd/compiler/README-ISA.md
View file

@ -206,6 +206,11 @@ Currently, we don't do this.
This leads to wrong bounds checking, using a VGPR offset fixes it.
## unused VMEM/DS destination lanes can't be used without waiting
On GFX11, we can't safely read/write unused lanes of VMEM/DS destination
VGPRs without waiting for the load to finish.
## GCN / GFX6 hazards
### VINTRP followed by a read with `v_readfirstlane` or `v_readlane`

18
src/amd/compiler/aco_insert_waitcnt.cpp
View file

@ -224,14 +224,15 @@ struct wait_entry {
bool join(const wait_entry& other)
{
bool changed = (other.events & ~events) || (other.counters & ~counters) ||
(other.wait_on_read && !wait_on_read) || (other.vmem_types & !vmem_types);
(other.wait_on_read && !wait_on_read) || (other.vmem_types & !vmem_types) ||
(!other.logical && logical);
events |= other.events;
counters |= other.counters;
changed |= imm.combine(other.imm);
changed |= delay.combine(other.delay);
wait_on_read |= other.wait_on_read;
vmem_types |= other.vmem_types;
assert(logical == other.logical);
logical &= other.logical;
return changed;
}
@ -736,7 +737,7 @@ update_counters_for_flat_load(wait_ctx& ctx, memory_sync_info sync = memory_sync
void
insert_wait_entry(wait_ctx& ctx, PhysReg reg, RegClass rc, wait_event event, bool wait_on_read,
uint8_t vmem_types = 0, unsigned cycles = 0)
uint8_t vmem_types = 0, unsigned cycles = 0, bool force_linear = false)
{
uint16_t counters = get_counters_for_event(event);
wait_imm imm;
@ -760,7 +761,7 @@ insert_wait_entry(wait_ctx& ctx, PhysReg reg, RegClass rc, wait_event event, boo
delay.salu_cycles = cycles;
}
wait_entry new_entry(event, imm, delay, !rc.is_linear(), wait_on_read);
wait_entry new_entry(event, imm, delay, !rc.is_linear() && !force_linear, wait_on_read);
new_entry.vmem_types |= vmem_types;
for (unsigned i = 0; i < rc.size(); i++) {
@ -781,7 +782,14 @@ void
insert_wait_entry(wait_ctx& ctx, Definition def, wait_event event, uint8_t vmem_types = 0,
unsigned cycles = 0)
{
insert_wait_entry(ctx, def.physReg(), def.regClass(), event, true, vmem_types, cycles);
/* We can't safely write to unwritten destination VGPR lanes on GFX11 without waiting for
* the load to finish.
*/
bool force_linear =
ctx.gfx_level >= GFX11 && (event & (event_lds | event_gds | event_vmem | event_flat));
insert_wait_entry(ctx, def.physReg(), def.regClass(), event, true, vmem_types, cycles,
force_linear);
}
void