[Mesa-dev] [PATCH 5/6] i965/vec4: Propagate conditional modifiers from compares to adds
Ian Romanick
idr at freedesktop.org
Thu Mar 22 18:05:56 UTC 2018
On 03/22/2018 01:12 AM, Alejandro Piñeiro wrote:
> Any reason to not add tests on test_vec4_cmod_propagation as the fs
> equivalent did?
Laziness. :)
> Also, two small comments below.
>
> On 22/03/18 01:58, Ian Romanick wrote:
>> From: Ian Romanick <ian.d.romanick at intel.com>
>>
>> No changes on Broadwell and later becuase those plaforms do not use the
>> vec4 backend at all.
>
> typo: becuase -> because
And plaforms -> platforms. I'll fix those.
>> Ivy Bridge and Haswell had similar results. (Ivy Bridge shown)
>> total instructions in shared programs: 11682119 -> 11681056 (<.01%)
>> instructions in affected programs: 150403 -> 149340 (-0.71%)
>> helped: 950
>> HURT: 0
>> helped stats (abs) min: 1 max: 16 x̄: 1.12 x̃: 1
>> helped stats (rel) min: 0.23% max: 2.78% x̄: 0.82% x̃: 0.71%
>> 95% mean confidence interval for instructions value: -1.19 -1.04
>> 95% mean confidence interval for instructions %-change: -0.84% -0.79%
>> Instructions are helped.
>>
>> total cycles in shared programs: 257495842 -> 257495238 (<.01%)
>> cycles in affected programs: 270302 -> 269698 (-0.22%)
>> helped: 271
>> HURT: 13
>> helped stats (abs) min: 2 max: 14 x̄: 2.42 x̃: 2
>> helped stats (rel) min: 0.06% max: 1.13% x̄: 0.32% x̃: 0.28%
>> HURT stats (abs) min: 2 max: 12 x̄: 4.00 x̃: 4
>> HURT stats (rel) min: 0.15% max: 1.18% x̄: 0.30% x̃: 0.26%
>> 95% mean confidence interval for cycles value: -2.41 -1.84
>> 95% mean confidence interval for cycles %-change: -0.31% -0.26%
>> Cycles are helped.
>>
>> Sandy Bridge
>> total instructions in shared programs: 10430493 -> 10429727 (<.01%)
>> instructions in affected programs: 120860 -> 120094 (-0.63%)
>> helped: 766
>> HURT: 0
>> helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
>> helped stats (rel) min: 0.30% max: 2.70% x̄: 0.78% x̃: 0.73%
>> 95% mean confidence interval for instructions value: -1.00 -1.00
>> 95% mean confidence interval for instructions %-change: -0.80% -0.75%
>> Instructions are helped.
>>
>> total cycles in shared programs: 146138718 -> 146138446 (<.01%)
>> cycles in affected programs: 244114 -> 243842 (-0.11%)
>> helped: 132
>> HURT: 0
>> helped stats (abs) min: 2 max: 4 x̄: 2.06 x̃: 2
>> helped stats (rel) min: 0.03% max: 0.43% x̄: 0.16% x̃: 0.19%
>> 95% mean confidence interval for cycles value: -2.12 -2.00
>> 95% mean confidence interval for cycles %-change: -0.18% -0.15%
>> Cycles are helped.
>>
>> GM45 and Iron Lake had identical results. (Iron Lake shown)
>> total instructions in shared programs: 7780251 -> 7780248 (<.01%)
>> instructions in affected programs: 175 -> 172 (-1.71%)
>> helped: 3
>> HURT: 0
>> helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
>> helped stats (rel) min: 1.49% max: 2.44% x̄: 1.81% x̃: 1.49%
>>
>> total cycles in shared programs: 177851584 -> 177851578 (<.01%)
>> cycles in affected programs: 9796 -> 9790 (-0.06%)
>> helped: 3
>> HURT: 0
>> helped stats (abs) min: 2 max: 2 x̄: 2.00 x̃: 2
>> helped stats (rel) min: 0.05% max: 0.08% x̄: 0.06% x̃: 0.05%
>>
>> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
>> ---
>> src/intel/compiler/brw_vec4_cmod_propagation.cpp | 70 ++++++++++++++++++++++--
>> 1 file changed, 65 insertions(+), 5 deletions(-)
>>
>> diff --git a/src/intel/compiler/brw_vec4_cmod_propagation.cpp b/src/intel/compiler/brw_vec4_cmod_propagation.cpp
>> index 7f1001b..5205da4 100644
>> --- a/src/intel/compiler/brw_vec4_cmod_propagation.cpp
>> +++ b/src/intel/compiler/brw_vec4_cmod_propagation.cpp
>> @@ -50,8 +50,14 @@ opt_cmod_propagation_local(bblock_t *block)
>> inst->predicate != BRW_PREDICATE_NONE ||
>> !inst->dst.is_null() ||
>> (inst->src[0].file != VGRF && inst->src[0].file != ATTR &&
>> - inst->src[0].file != UNIFORM) ||
>> - inst->src[0].abs)
>> + inst->src[0].file != UNIFORM))
>> + continue;
>> +
>> + /* An ABS source modifier can only be handled when processing a compare
>> + * with a value other than zero.
>> + */
>> + if (inst->src[0].abs &&
>> + (inst->opcode != BRW_OPCODE_CMP || inst->src[1].is_zero()))
>> continue;
>>
>> if (inst->opcode == BRW_OPCODE_AND &&
>> @@ -60,15 +66,68 @@ opt_cmod_propagation_local(bblock_t *block)
>> !inst->src[0].negate))
>> continue;
>>
>> - if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero())
>> - continue;
>> -
>> if (inst->opcode == BRW_OPCODE_MOV &&
>> inst->conditional_mod != BRW_CONDITIONAL_NZ)
>> continue;
>>
>> bool read_flag = false;
>> foreach_inst_in_block_reverse_starting_from(vec4_instruction, scan_inst, inst) {
>> + /* A CMP with a second source of zero can match with anything. A CMP
>> + * with a second source that is not zero can only match with an ADD
>> + * instruction.
>> + */
>> + if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero()) {
>> + bool negate;
>> +
>> + if (scan_inst->opcode != BRW_OPCODE_ADD)
>> + goto not_match;
>> +
>> + /* A CMP is basically a subtraction. The result of the
>> + * subtraction must be the same as the result of the addition.
>> + * This means that one of the operands must be negated. So (a +
>> + * b) vs (a == -b) or (a + -b) vs (a == b).
>> + */
>> + if ((inst->src[0].equals(scan_inst->src[0]) &&
>> + inst->src[1].negative_equals(scan_inst->src[1])) ||
>> + (inst->src[0].equals(scan_inst->src[1]) &&
>> + inst->src[1].negative_equals(scan_inst->src[0]))) {
>> + negate = false;
>> + } else if ((inst->src[0].negative_equals(scan_inst->src[0]) &&
>> + inst->src[1].equals(scan_inst->src[1])) ||
>> + (inst->src[0].negative_equals(scan_inst->src[1]) &&
>> + inst->src[1].equals(scan_inst->src[0]))) {
>> + negate = true;
>> + } else {
>> + goto not_match;
>> + }
>> +
>> + if (scan_inst->exec_size != inst->exec_size ||
>> + scan_inst->group != inst->group)
>> + goto not_match;
>> +
>> + /* From the Sky Lake PRM Vol. 7 "Assigning Conditional Mods":
>> + *
>> + * * Note that the [post condition signal] bits generated at
>> + * the output of a compute are before the .sat.
>> + *
>> + * So we don't have to bail if scan_inst has saturate.
>> + */
>
> As Skylake doesn't use vec4, this comment is superfluous (I guess that
> it is a C&P from the fs equivalent).
It also exists in the old path in this file. I was going to change it
to reference a different PRM, but the same reference was already in this
file. None of that shows up in this diff.
>> +
>> + /* Otherwise, try propagating the conditional. */
>> + const enum brw_conditional_mod cond =
>> + negate ? brw_swap_cmod(inst->conditional_mod)
>> + : inst->conditional_mod;
>> +
>> + if (scan_inst->can_do_cmod() &&
>> + ((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) ||
>> + scan_inst->conditional_mod == cond)) {
>> + scan_inst->conditional_mod = cond;
>> + inst->remove(block);
>> + progress = true;
>> + }
>> + break;
>> + }
>> +
>> if (regions_overlap(inst->src[0], inst->size_read(0),
>> scan_inst->dst, scan_inst->size_written)) {
>> if ((scan_inst->predicate && scan_inst->opcode != BRW_OPCODE_SEL) ||
>> @@ -170,6 +229,7 @@ opt_cmod_propagation_local(bblock_t *block)
>> break;
>> }
>>
>> + not_match:
>> if (scan_inst->writes_flag())
>> break;
>>
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