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Functions: improve compiler optimizability of multi-function evaluation 

This simplifies the code enough so that msvc is able to unroll and
vectorize some multi-functions like simple addition.

The performance improvements are almost as good as the GCC
improvements shown in D16942 (for add and multiply at least).
This commit is contained in:
Jacques Lucke 2023-01-08 15:04:51 +01:00
parent d4c085c17d
commit 5f9a48ed59
Notes: blender-bot 2023-02-13 13:38:09 +01:00 
Referenced by issue #103737, Functions: Improve multi-function evaluation to support loop optimizations with msvc.
1 changed files with 14 additions and 19 deletions
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33
source/blender/functions/FN_multi_function_builder.hh
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@ -138,23 +138,18 @@ execute_array(TypeSequence<ParamTags...> /*param_tags*/,
* other. This is important for some compiler optimizations. */
Args &&__restrict... args)
{
for (const int64_t i : mask) {
element_fn([&]() -> decltype(auto) {
using ParamTag = typename TypeSequence<ParamTags...>::template at_index<I>;
if constexpr (ParamTag::category == ParamCategory::SingleInput) {
/* For inputs, pass the value (or a reference to it) to the function. */
return args[i];
}
else if constexpr (ParamTag::category == ParamCategory::SingleOutput) {
/* For outputs, pass a pointer to the function. This is done instead of passing a
* reference, because the pointer points to uninitialized memory. */
return args + i;
}
else if constexpr (ParamTag::category == ParamCategory::SingleMutable) {
/* For mutables, pass a mutable reference to the function. */
return args[i];
}
}()...);
if constexpr (std::is_same_v<std::decay_t<MaskT>, IndexRange>) {
/* Having this explicit loop is necessary for msvc to be able to vectorize this. */
const int64_t start = mask.start();
const int64_t end = mask.one_after_last();
for (int64_t i = start; i < end; i++) {
element_fn(args[i]...);
}
}
else {
for (const int32_t i : mask) {
element_fn(args[i]...);
}
}
}
@ -190,7 +185,7 @@ inline void execute_materialized_impl(TypeSequence<ParamTags...> /*param_tags*/,
return chunks[in_i];
}
else if constexpr (ParamTag::category == ParamCategory::SingleOutput) {
return chunks + out_i;
return chunks[out_i];
}
else if constexpr (ParamTag::category == ParamCategory::SingleMutable) {
return chunks[out_i];
@ -472,7 +467,7 @@ inline auto build_multi_function_with_n_inputs_one_output(const char *name,
constexpr auto param_tags = TypeSequence<MFParamTag<ParamCategory::SingleInput, In>...,
MFParamTag<ParamCategory::SingleOutput, Out>>();
auto call_fn = build_multi_function_call_from_element_fn(
[element_fn](const In &...in, Out *out) { new (out) Out(element_fn(in...)); },
[element_fn](const In &...in, Out &out) { new (&out) Out(element_fn(in...)); },
exec_preset,
param_tags);
return CustomMF(name, call_fn, param_tags);