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[wasm] Make the number of locals available faster

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Operations on locals are the most common wasm operations (especially
local.get), and just computing the number of locals from the vector
shows up with a few percent in the profile. Storing this number
separately removes a few percent of execution time from the
{DecodeLocalGet} method.

R=thibaudm@chromium.org

Bug: v8:10576
Change-Id: I9c12842c944e4ad2e602e05838948a33922ff438
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2429950
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70148}
This commit is contained in:
Clemens Backes 2020-09-25 13:50:53 +02:00 committed by Commit Bot
parent f50d8c7840
commit 65c15f4fe3
1 changed files with 10 additions and 2 deletions
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12
src/wasm/function-body-decoder-impl.h
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@ -1002,7 +1002,8 @@ class WasmDecoder : public Decoder {
Zone* zone() const { return local_types_.get_allocator().zone(); }
uint32_t num_locals() const {
return static_cast<uint32_t>(local_types_.size());
DCHECK_EQ(num_locals_, local_types_.size());
return num_locals_;
}
ValueType local_type(uint32_t index) const { return local_types_[index]; }
@ -1011,12 +1012,13 @@ class WasmDecoder : public Decoder {
DCHECK_NOT_NULL(sig_);
DCHECK_EQ(0, this->local_types_.size());
local_types_.assign(sig_->parameters().begin(), sig_->parameters().end());
num_locals_ = static_cast<uint32_t>(sig_->parameters().size());
}
// Decodes local definitions in the current decoder.
// Returns true iff locals are found.
// Writes the total length of decoded locals in 'total_length'.
// If insert_postion is present, the decoded locals will be inserted into the
// If insert_position is present, the decoded locals will be inserted into the
// 'local_types_' of this decoder. Otherwise, this function is used just to
// check validity and determine the encoding length of the locals in bytes.
// The decoder's pc is not advanced. If no locals are found (i.e., no
@ -1072,6 +1074,7 @@ class WasmDecoder : public Decoder {
// Move the insertion iterator to the end of the newly inserted locals.
insert_iterator =
local_types_.insert(insert_iterator, count, type) + count;
num_locals_ += count;
}
}
DCHECK(ok());
@ -1899,6 +1902,10 @@ class WasmDecoder : public Decoder {
// needed (see {zone()} accessor below).
ZoneVector<ValueType> local_types_;
// Cached value, for speed (yes, it's measurably faster to load this value
// than to load the start and end pointer from a vector, subtract and shift).
uint32_t num_locals_ = 0;
const WasmModule* module_;
const WasmFeatures enabled_;
WasmFeatures* detected_;
@ -2434,6 +2441,7 @@ class WasmFullDecoder : public WasmDecoder<validate> {
if (c->is_let()) {
this->local_types_.erase(this->local_types_.begin(),
this->local_types_.begin() + c->locals_count);
this->num_locals_ -= c->locals_count;
CALL_INTERFACE_IF_REACHABLE(DeallocateLocals, c->locals_count);
}
if (!TypeCheckFallThru()) return 0;