[Mesa-dev] [PATCH 5/6] i965/vec4: Propagate conditional modifiers from compares to adds
Alejandro Piñeiro
apinheiro at igalia.com
Fri Mar 23 08:19:43 UTC 2018
On 22/03/18 19:05, Ian Romanick wrote:
> 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. :)
Ok, I guess that those could be added later on a different patch,
independently of this one.
>> 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.
Oh true, the file already had other Sky Lake PRM references. Then I
guess that it is okish to add a new one (although bonus points if in the
future someone update all the PRM references).
In any case, the patch:
Reviewed-by: Alejandro Piñeiro <apinheiro at igalia.com>
>
>>> +
>>> + /* 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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