Module: Mesa Branch: staging/21.3 Commit: 78098039f3c9b6a18d9f0cdbda5cf90c4ec412e3 URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=78098039f3c9b6a18d9f0cdbda5cf90c4ec412e3
Author: Alyssa Rosenzweig <[email protected]> Date: Thu Feb 17 19:33:29 2022 -0500 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 <[email protected]> Cc: mesa-stable Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15072> (cherry picked from commit 8e0eb592d5bbcf00f8bed55cc95013abf77fad12) --- .pick_status.json | 2 +- src/panfrost/bifrost/bi_opt_mod_props.c | 28 +++++++++++++++++++++++++--- 2 files changed, 26 insertions(+), 4 deletions(-) diff --git a/.pick_status.json b/.pick_status.json index 21bfac84d72..3a4da06c144 100644 --- a/.pick_status.json +++ b/.pick_status.json @@ -490,7 +490,7 @@ "description": "pan/bi: Avoid *FADD.v2f16 hazard in optimizer", "nominated": true, "nomination_type": 0, - "resolution": 0, + "resolution": 1, "main_sha": null, "because_sha": null }, diff --git a/src/panfrost/bifrost/bi_opt_mod_props.c b/src/panfrost/bifrost/bi_opt_mod_props.c index 44eae29bd62..ce06f9596ad 100644 --- a/src/panfrost/bifrost/bi_opt_mod_props.c +++ b/src/panfrost/bifrost/bi_opt_mod_props.c @@ -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; }
