KonstantinSeurer
/
mesa
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

pan/bi: Avoid *FADD.v2f16 hazard in optimizer 

This is a very obscure encoding restriction in the Bifrost ISA. Unknown if any
real apps or tests hit this, but we still need to get it right sadly.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15072>
This commit is contained in:
Alyssa Rosenzweig 2022-02-17 19:33:29 -05:00 committed by Marge Bot
parent c2178d09d0
commit 8e0eb592d5
1 changed files with 25 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
src/panfrost/bifrost/bi_opt_mod_props.c
View File

@ -25,6 +25,18 @@
#include "compiler.h"
#include "bi_builder.h"
/*
* Due to a Bifrost encoding restriction, some instructions cannot have an abs
* modifier on both sources. Check if adding a fabs modifier to a given source
* of a binary instruction would cause this restriction to be hit.
*/
static bool
bi_would_impact_abs(unsigned arch, bi_instr *I, bi_index repl, unsigned s)
{
return (arch <= 8) && I->src[1 - s].abs &&
bi_is_word_equiv(I->src[1 - s], repl);
}
static bool
bi_takes_fabs(unsigned arch, bi_instr *I, bi_index repl, unsigned s)
{
@ -32,9 +44,15 @@ bi_takes_fabs(unsigned arch, bi_instr *I, bi_index repl, unsigned s)
case BI_OPCODE_FCMP_V2F16:
case BI_OPCODE_FMAX_V2F16:
case BI_OPCODE_FMIN_V2F16:
/* Bifrost encoding restriction: can't have both abs if equal sources */
return !(arch <= 8 && I->src[1 - s].abs
&& bi_is_word_equiv(I->src[1 - s], repl));
return !bi_would_impact_abs(arch, I, repl, s);
case BI_OPCODE_FADD_V2F16:
/*
* For FADD.v2f16, the FMA pipe has the abs encoding hazard,
* while the FADD pipe cannot encode a clamp. Either case in
* isolation can be worked around in the scheduler, but both
* together is impossible to encode. Avoid the hazard.
*/
return !(I->clamp && bi_would_impact_abs(arch, I, repl, s));
case BI_OPCODE_V2F32_TO_V2F16:
/* TODO: Needs both match or lower */
return false;
@ -182,6 +200,10 @@ bi_takes_clamp(bi_instr *I)
case BI_OPCODE_FMA_RSCALE_V2F16:
case BI_OPCODE_FADD_RSCALE_F32:
return false;
case BI_OPCODE_FADD_V2F16:
/* Encoding restriction */
return !(I->src[0].abs && I->src[1].abs &&
bi_is_word_equiv(I->src[0], I->src[1]));
default:
return bi_opcode_props[I->op].clamp;
}