Hi,
there is nothing exciting in this patch. I measured latencies and also
compared them with newly released optimization guide and it seems that
only important change is that addss is fastr now. It can be 2 cycles
instaead of 3 in some cases when the input parameter is computed by
another addition. The throughput has increased but we have no model for
that.
I added comments whic should make it easier to update the table for
future revisions.
I also increased the large insn bound since decoders seems no longer
require instructions to be 8 bytes or less.
Bootstrapped/rgtested x86_64-linux, comitted.
gcc/ChangeLog:
* config/i386/x86-tune-costs.h (znver5_cost): Update instruction
costs.
diff --git a/gcc/config/i386/x86-tune-costs.h b/gcc/config/i386/x86-tune-costs.h
index b90567fbbf2..1b3227ace16 100644
--- a/gcc/config/i386/x86-tune-costs.h
+++ b/gcc/config/i386/x86-tune-costs.h
@@ -2034,6 +2034,7 @@ struct processor_costs znver5_cost = {
COSTS_N_INSNS (1), /* cost of a lea instruction. */
COSTS_N_INSNS (1), /* variable shift costs. */
COSTS_N_INSNS (1), /* constant shift costs. */
+ /* mul has latency 3, executes in 3 integer units. */
{COSTS_N_INSNS (3), /* cost of starting multiply for QI. */
COSTS_N_INSNS (3), /* HI. */
COSTS_N_INSNS (3), /* SI. */
@@ -2041,6 +2042,8 @@ struct processor_costs znver5_cost = {
COSTS_N_INSNS (3)}, /* other. */
0, /* cost of multiply per each bit
set. */
+ /* integer divide has latency of 8 cycles
+ plus 1 for every 9 bits of quotient. */
{COSTS_N_INSNS (10), /* cost of a divide/mod for QI. */
COSTS_N_INSNS (11), /* HI. */
COSTS_N_INSNS (13), /* SI. */
@@ -2048,7 +2051,7 @@ struct processor_costs znver5_cost = {
COSTS_N_INSNS (16)}, /*
other. */
COSTS_N_INSNS (1), /* cost of movsx. */
COSTS_N_INSNS (1), /* cost of movzx. */
- 8, /* "large" insn. */
+ 15, /* "large" insn. */
9, /* MOVE_RATIO. */
6, /* CLEAR_RATIO */
{6, 6, 6}, /* cost of loading integer registers
@@ -2065,12 +2068,13 @@ struct processor_costs znver5_cost = {
2, 2, 2, /* cost of moving XMM,YMM,ZMM
register. */
6, /* cost of moving SSE register to
integer. */
- /* VGATHERDPD is 17 uops and throughput is 4, VGATHERDPS is 24 uops,
- throughput 5. Approx 7 uops do not depend on vector size and every load
- is 5 uops. */
+
+ /* TODO: gather and scatter instructions are currently disabled in
+ x86-tune.def. In some cases they are however a win, see PR116582
+ We however need good cost model for them. */
14, 10, /* Gather load static, per_elt. */
14, 20, /* Gather store static, per_elt. */
- 32, /* size of l1 cache. */
+ 48, /* size of l1 cache. */
1024, /* size of l2 cache. */
64, /* size of prefetch block. */
/* New AMD processors never drop prefetches; if they cannot be performed
@@ -2080,6 +2084,8 @@ struct processor_costs znver5_cost = {
time). */
100, /* number of parallel prefetches. */
3, /* Branch cost. */
+ /* TODO x87 latencies are still based on znver4.
+ Probably not very important these days. */
COSTS_N_INSNS (7), /* cost of FADD and FSUB insns. */
COSTS_N_INSNS (7), /* cost of FMUL instruction. */
/* Latency of fdiv is 8-15. */
@@ -2089,16 +2095,24 @@ struct processor_costs znver5_cost = {
/* Latency of fsqrt is 4-10. */
COSTS_N_INSNS (25), /* cost of FSQRT instruction. */
+ /* SSE instructions have typical throughput 4 and latency 1. */
COSTS_N_INSNS (1), /* cost of cheap SSE instruction. */
- COSTS_N_INSNS (3), /* cost of ADDSS/SD SUBSS/SD insns. */
+ /* ADDSS has throughput 2 and latency 2
+ (in some cases when source is another addition). */
+ COSTS_N_INSNS (2), /* cost of ADDSS/SD SUBSS/SD insns. */
+ /* MULSS has throughput 2 and latency 3. */
COSTS_N_INSNS (3), /* cost of MULSS instruction. */
COSTS_N_INSNS (3), /* cost of MULSD instruction. */
+ /* FMA had throughput 2 and latency 4. */
COSTS_N_INSNS (4), /* cost of FMA SS instruction. */
COSTS_N_INSNS (4), /* cost of FMA SD instruction. */
+ /* DIVSS has throughtput 0.4 and latency 10. */
COSTS_N_INSNS (10), /* cost of DIVSS instruction. */
- /* 9-13. */
+ /* DIVSD has throughtput 0.25 and latency 13. */
COSTS_N_INSNS (13), /* cost of DIVSD instruction. */
+ /* DIVSD has throughtput 0.22 and latency 14. */
COSTS_N_INSNS (14), /* cost of SQRTSS instruction. */
+ /* DIVSD has throughtput 0.13 and latency 20. */
COSTS_N_INSNS (20), /* cost of SQRTSD instruction. */
/* Zen5 can execute:
- integer ops: 6 per cycle, at most 3 multiplications.
