From f0ab3de6ec0e3540f2e57f3f5628005f0a4e3fa5 Mon Sep 17 00:00:00 2001
From: Jan Hubicka <jh@suse.cz>
Date: Tue, 3 Sep 2024 18:20:34 +0200
Subject: [PATCH] Zen5 tuning part 4: update reassocation width
Zen5 has 6 instead of 4 ALUs and the integer multiplication can now execute in
3 of them. FP units can do 2 additions and 2 multiplications with latency 2
and 3. This patch updates reassociation width accordingly. This has potential
of increasing register pressure but unlike while benchmarking znver1 tuning
I did not noticed this actually causing problem on spec, so this patch bumps
up reassociation width to 6 for everything except for integer vectors, where
there are 4 units with typical latency of 1.
Bootstrapped/regtested x86_64-linux, comitted.
gcc/ChangeLog:
* config/i386/i386.cc (ix86_reassociation_width): Update for Znver5.
* config/i386/x86-tune-costs.h (znver5_costs): Update reassociation
widths.
---
gcc/config/i386/i386.cc | 10 +++++++---
gcc/config/i386/x86-tune-costs.h | 23 +++++++++++++----------
2 files changed, 20 insertions(+), 13 deletions(-)
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 7af9ceca429f..e8744fa77ead 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -24483,13 +24483,17 @@ ix86_reassociation_width (unsigned int op, machine_mode mode)
if (width == 1)
return 1;
- /* Integer vector instructions execute in FP unit
+ /* Znver1-4 Integer vector instructions execute in FP unit
and can execute 3 additions and one multiplication per cycle. */
if ((ix86_tune == PROCESSOR_ZNVER1 || ix86_tune == PROCESSOR_ZNVER2
- || ix86_tune == PROCESSOR_ZNVER3 || ix86_tune == PROCESSOR_ZNVER4
- || ix86_tune == PROCESSOR_ZNVER5)
+ || ix86_tune == PROCESSOR_ZNVER3 || ix86_tune == PROCESSOR_ZNVER4)
&& INTEGRAL_MODE_P (mode) && op != PLUS && op != MINUS)
return 1;
+ /* Znver5 can do 2 integer multiplications per cycle with latency
+ of 3. */
+ if (ix86_tune == PROCESSOR_ZNVER5
+ && INTEGRAL_MODE_P (mode) && op != PLUS && op != MINUS)
+ width = 6;
/* Account for targets that splits wide vectors into multiple parts. */
if (TARGET_AVX512_SPLIT_REGS && GET_MODE_BITSIZE (mode) > 256)
diff --git a/gcc/config/i386/x86-tune-costs.h b/gcc/config/i386/x86-tune-costs.h
index 2bfaee554d53..b90567fbbf23 100644
--- a/gcc/config/i386/x86-tune-costs.h
+++ b/gcc/config/i386/x86-tune-costs.h
@@ -2100,16 +2100,19 @@ struct processor_costs znver5_cost = {
COSTS_N_INSNS (13), /* cost of DIVSD instruction. */
COSTS_N_INSNS (14), /* cost of SQRTSS instruction. */
COSTS_N_INSNS (20), /* cost of SQRTSD instruction. */
- /* Zen can execute 4 integer operations per cycle. FP operations
- take 3 cycles and it can execute 2 integer additions and 2
- multiplications thus reassociation may make sense up to with of 6.
- SPEC2k6 bencharks suggests
- that 4 works better than 6 probably due to register pressure.
-
- Integer vector operations are taken by FP unit and execute 3 vector
- plus/minus operations per cycle but only one multiply. This is adjusted
- in ix86_reassociation_width. */
- 4, 4, 3, 6, /* reassoc int, fp, vec_int, vec_fp. */
+ /* Zen5 can execute:
+ - integer ops: 6 per cycle, at most 3 multiplications.
+ latency 1 for additions, 3 for multiplications (pipelined)
+
+ Setting width of 9 for multiplication is probably excessive
+ for register pressure.
+ - fp ops: 2 additions per cycle, latency 2-3
+ 2 multiplicaitons per cycle, latency 3
+ - vector intger ops: 4 additions, latency 1
+ 2 multiplications, latency 4
+ We increase width to 6 for multiplications
+ in ix86_reassociation_width. */
+ 6, 6, 4, 6, /* reassoc int, fp, vec_int, vec_fp. */
znver2_memcpy,
znver2_memset,
COSTS_N_INSNS (4), /* cond_taken_branch_cost. */
--
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