Revert "Micro-optimizations in CollectMatchingRulesForListInternal."

This reverts commit cf2358b.

Reason for revert: Causes memory regressions.

Original change's description:
> Micro-optimizations in CollectMatchingRulesForListInternal.
>
> Combine four optimizations that are too small to measure individually,
> but that together benchmark positive:
>
>  - Make CascadeLayerMap::kImplicitOuterLayerOrder a true constant,
>    so that the compiler doesn't have to load it from the binary
>    every time. (Fix resulting warning coming from implicit cast.)
>  - Don't count number of rejected rules separately; calculate it
>    at the end instead if needed. (This saves a register.)
>  - Don't refcount result.custom_highlight_name, especially as it's
>    almost never actually set.
>  - Store the Bloom filter directly in SelectorFilter, instead of
>    going through a pointer indirection every time. This also keeps
>    it from being allocated and deallocated every time we go hit the
>    uppermost element; we just clear it instead.
>
> Style microbenchmarks (Zen 3, LTO but no PGO):
>
> Initial style (µs)     Before     After    Perf      95% CI (BCa)
> =================== ========= ========= ======= =================
> ECommerce                8041      8015   +0.3%  [ -0.6%,  +1.0%]
> Encyclopedia            71498     70901   +0.8%  [ +0.2%,  +1.4%]
> Extension              166003    164651   +0.8%  [ +0.3%,  +1.3%]
> News                    31801     31391   +1.3%  [ +0.5%,  +1.8%]
> Search                   2164      2149   +0.7%  [ -0.1%,  +1.4%]
> Social1                 18797     18510   +1.5%  [ +0.8%,  +2.3%]
> Social2                   797       795   +0.3%  [ -0.4%,  +0.9%]
> Sports                  26062     26132   -0.3%  [ -0.9%,  +0.3%]
> Video                   31769     31868   -0.3%  [ -0.9%,  +0.4%]
> Geometric mean                            +0.6%  [ +0.3%,  +0.7%]
>
> Recalc style (µs)      Before     After    Perf      95% CI (BCa)
> =================== ========= ========= ======= =================
> ECommerce                9250      9240   +0.1%  [ -0.8%,  +0.7%]
> Encyclopedia            63747     63213   +0.8%  [ +0.1%,  +1.6%]
> Extension              164301    163611   +0.4%  [ -0.2%,  +0.9%]
> News                    23482     23118   +1.6%  [ +0.7%,  +2.2%]
> Search                    182       181   +0.5%  [ -0.9%,  +1.9%]
> Social1                 13178     12913   +2.0%  [ +1.4%,  +2.7%]
> Social2                   395       392   +0.7%  [ -0.2%,  +2.1%]
> Sports                  19213     19090   +0.6%  [ -0.1%,  +1.2%]
> Video                   19874     19708   +0.8%  [ -0.1%,  +1.5%]
> Geometric mean                            +0.9%  [ +0.5%,  +1.1%]
>
> Change-Id: I5aba1a57bdcfeba735154be814e1bd2532816e02
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3810556
> Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
> Commit-Queue: Steinar H Gunderson <sesse@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1031876}

Change-Id: I537af3d9563471e5fd35fa80ca7655ba83a57a47
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3812172
Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Steinar H Gunderson <sesse@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1032477}

third_party/blink/renderer/core/css/cascade_layer_map.cc

@@ -7,6 +7,10 @@
 #include "third_party/blink/renderer/core/css/rule_set.h"
 
 namespace blink {
+
+const unsigned CascadeLayerMap::kImplicitOuterLayerOrder =
+    std::numeric_limits<unsigned>::max();
+
 namespace {
 
 using CanonicalLayerMap =

third_party/blink/renderer/core/css/cascade_layer_map.h

@@ -17,8 +17,7 @@ namespace blink {
 // layers in each sheet to the sorted layer order number.
 class CORE_EXPORT CascadeLayerMap : public GarbageCollected<CascadeLayerMap> {
  public:
-  static constexpr unsigned kImplicitOuterLayerOrder =
-      std::numeric_limits<unsigned>::max();
+  static const unsigned kImplicitOuterLayerOrder;
 
   explicit CascadeLayerMap(const ActiveStyleSheetVector&);
 

third_party/blink/renderer/core/css/element_rule_collector.cc

@@ -351,13 +351,14 @@ void ElementRuleCollector::CollectMatchingRulesForListInternal(
       rule_set->ContainerQueryIntervals());
   Seeker<StyleScope> scope_seeker(rule_set->ScopeIntervals());
 
+  unsigned rejected = 0;
   unsigned fast_rejected = 0;
   unsigned matched = 0;
   SelectorStatisticsCollector selector_statistics_collector;
   if (perf_trace_enabled)
     selector_statistics_collector.ReserveCapacity(rules->size());
 
-  for (const RuleData& rule_data : *rules) {
+  for (const auto& rule_data : *rules) {
     if (perf_trace_enabled) {
       selector_statistics_collector.EndCollectionForCurrentRule();
       selector_statistics_collector.BeginCollectionForRule(&rule_data);
@@ -381,6 +382,7 @@ void ElementRuleCollector::CollectMatchingRulesForListInternal(
     if (UNLIKELY(part_request && part_request->for_shadow_pseudo)) {
       if (!selector.IsAllowedAfterPart()) {
         DCHECK_EQ(selector.GetPseudoType(), CSSSelector::kPseudoPart);
+        rejected++;
         continue;
       }
       DCHECK_EQ(selector.Relation(), CSSSelector::kUAShadow);
@@ -394,10 +396,12 @@ void ElementRuleCollector::CollectMatchingRulesForListInternal(
     DCHECK(!context.is_inside_visited_link ||
            inside_link_ != EInsideLink::kNotInsideLink);
     if (!checker.Match(context, result)) {
+      rejected++;
       continue;
     }
     if (pseudo_style_request_.pseudo_id != kPseudoIdNone &&
         pseudo_style_request_.pseudo_id != result.dynamic_pseudo) {
+      rejected++;
       continue;
     }
     const ContainerQuery* container_query =
@@ -417,6 +421,7 @@ void ElementRuleCollector::CollectMatchingRulesForListInternal(
           result.dynamic_pseudo == kPseudoIdNone) {
         if (!EvaluateAndAddContainerQueries(*container_query,
                                             style_recalc_context_, result_)) {
+          rejected++;
           if (AffectsAnimations(rule_data))
             result_.SetConditionallyAffectsAnimations();
           continue;
@@ -442,7 +447,6 @@ void ElementRuleCollector::CollectMatchingRulesForListInternal(
   if (!style_engine.Stats())
     return;
 
-  unsigned rejected = rules->size() - fast_rejected - matched;
   INCREMENT_STYLE_STATS_COUNTER(style_engine, rules_rejected, rejected);
   INCREMENT_STYLE_STATS_COUNTER(style_engine, rules_fast_rejected,
                                 fast_rejected);
@@ -877,8 +881,7 @@ void ElementRuleCollector::DidMatchRule(
 
       if (dynamic_pseudo == kPseudoIdHighlight) {
         DCHECK(result.custom_highlight_name);
-        style_->SetHasCustomHighlightName(
-            AtomicString(result.custom_highlight_name));
+        style_->SetHasCustomHighlightName(result.custom_highlight_name);
       }
     } else if (dynamic_pseudo == kPseudoIdFirstLine && container_query) {
       style_->SetFirstLineDependsOnSizeContainerQueries(true);

third_party/blink/renderer/core/css/resolver/style_resolver_test.cc

@@ -1433,7 +1433,7 @@ TEST_F(StyleResolverTest, NoCascadeLayers) {
   ASSERT_EQ(properties.size(), 3u);
 
   const uint16_t kImplicitOuterLayerOrder =
-      ClampTo<uint16_t>(CascadeLayerMap::kImplicitOuterLayerOrder);
+      CascadeLayerMap::kImplicitOuterLayerOrder;
 
   // div { display: block; }
   EXPECT_TRUE(properties[0].properties->HasProperty(CSSPropertyID::kDisplay));
@@ -1480,7 +1480,7 @@ TEST_F(StyleResolverTest, CascadeLayersInDifferentSheets) {
   ASSERT_EQ(properties.size(), 4u);
 
   const uint16_t kImplicitOuterLayerOrder =
-      ClampTo<uint16_t>(CascadeLayerMap::kImplicitOuterLayerOrder);
+      CascadeLayerMap::kImplicitOuterLayerOrder;
 
   // div { display: block; }
   EXPECT_TRUE(properties[0].properties->HasProperty(CSSPropertyID::kDisplay));
@@ -1539,7 +1539,7 @@ TEST_F(StyleResolverTest, CascadeLayersInDifferentTreeScopes) {
   ASSERT_EQ(properties.size(), 3u);
 
   const uint16_t kImplicitOuterLayerOrder =
-      ClampTo<uint16_t>(CascadeLayerMap::kImplicitOuterLayerOrder);
+      CascadeLayerMap::kImplicitOuterLayerOrder;
 
   // div { display: block }
   EXPECT_TRUE(properties[0].properties->HasProperty(CSSPropertyID::kDisplay));
@@ -1593,7 +1593,7 @@ TEST_F(StyleResolverTest, CascadeLayersAfterModifyingAnotherSheet) {
   ASSERT_EQ(properties.size(), 2u);
 
   const uint16_t kImplicitOuterLayerOrder =
-      ClampTo<uint16_t>(CascadeLayerMap::kImplicitOuterLayerOrder);
+      CascadeLayerMap::kImplicitOuterLayerOrder;
 
   // @layer { target { color: red } }"
   EXPECT_TRUE(properties[0].properties->HasProperty(CSSPropertyID::kColor));

third_party/blink/renderer/core/css/selector_checker.cc

@@ -1661,7 +1661,7 @@ bool SelectorChecker::CheckPseudoElement(const SelectorCheckingContext& context,
       // elements we have a single flag for tracking whether an element may
       // match _any_ ::highlight() element (kPseudoIdHighlight).
       if (!pseudo_argument_ || pseudo_argument_ == selector.Argument()) {
-        result.custom_highlight_name = selector.Argument().Impl();
+        result.custom_highlight_name = selector.Argument();
         return true;
       }
       return false;

third_party/blink/renderer/core/css/selector_checker.h

@@ -191,11 +191,7 @@ class CORE_EXPORT SelectorChecker {
 
    public:
     PseudoId dynamic_pseudo{kPseudoIdNone};
-
-    // Comes from an AtomicString, but not stored as one to avoid
-    // the cost of checking the refcount on cleaning up from every
-    // Match() call. Owned by the CSS selector it came from.
-    StringImpl* custom_highlight_name{nullptr};
+    AtomicString custom_highlight_name;
 
     // From the :has() argument selector checking, we need to get the element
     // that matches the leftmost compound selector to mark all possible :has()

third_party/blink/renderer/core/css/selector_filter.cc

@@ -120,6 +120,7 @@ inline void CollectDescendantSelectorIdentifierHashes(
 }  // namespace
 
 void SelectorFilter::PushParentStackFrame(Element& parent) {
+  DCHECK(ancestor_identifier_filter_);
   DCHECK(parent_stack_.IsEmpty() ||
          parent_stack_.back().element ==
              FlatTreeTraversal::ParentElement(parent));
@@ -131,21 +132,22 @@ void SelectorFilter::PushParentStackFrame(Element& parent) {
   CollectElementIdentifierHashes(parent, parent_frame.identifier_hashes);
   wtf_size_t count = parent_frame.identifier_hashes.size();
   for (wtf_size_t i = 0; i < count; ++i)
-    ancestor_identifier_filter_.Add(parent_frame.identifier_hashes[i]);
+    ancestor_identifier_filter_->Add(parent_frame.identifier_hashes[i]);
 }
 
 void SelectorFilter::PopParentStackFrame() {
   DCHECK(!parent_stack_.IsEmpty());
+  DCHECK(ancestor_identifier_filter_);
   const ParentStackFrame& parent_frame = parent_stack_.back();
   wtf_size_t count = parent_frame.identifier_hashes.size();
   for (wtf_size_t i = 0; i < count; ++i)
-    ancestor_identifier_filter_.Remove(parent_frame.identifier_hashes[i]);
+    ancestor_identifier_filter_->Remove(parent_frame.identifier_hashes[i]);
   parent_stack_.pop_back();
   if (parent_stack_.IsEmpty()) {
 #if DCHECK_IS_ON()
-    DCHECK(ancestor_identifier_filter_.LikelyEmpty());
+    DCHECK(ancestor_identifier_filter_->LikelyEmpty());
 #endif
-    ancestor_identifier_filter_.Clear();
+    ancestor_identifier_filter_.reset();
   }
 }
 
@@ -154,12 +156,12 @@ void SelectorFilter::PushParent(Element& parent) {
   DCHECK(parent.InActiveDocument());
   if (parent_stack_.IsEmpty()) {
     DCHECK_EQ(parent, parent.GetDocument().documentElement());
-#if DCHECK_IS_ON()
-    DCHECK(ancestor_identifier_filter_.IsClear());
-#endif
+    DCHECK(!ancestor_identifier_filter_);
+    ancestor_identifier_filter_ = std::make_unique<IdentifierFilter>();
     PushParentStackFrame(parent);
     return;
   }
+  DCHECK(ancestor_identifier_filter_);
   // We may get invoked for some random elements in some wacky cases during
   // style resolve. Pause maintaining the stack in this case.
   if (parent_stack_.back().element != FlatTreeTraversal::ParentElement(parent))

third_party/blink/renderer/core/css/selector_filter.h

@@ -31,6 +31,8 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CSS_SELECTOR_FILTER_H_
 #define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_SELECTOR_FILTER_H_
 
+#include <memory>
+
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/dom/element.h"
 #include "third_party/blink/renderer/platform/wtf/bloom_filter.h"
@@ -118,15 +120,16 @@ class CORE_EXPORT SelectorFilter {
   // With 100 unique strings in the filter, 2^12 slot table has false positive
   // rate of ~0.2%.
   using IdentifierFilter = CountingBloomFilter<12>;
-  IdentifierFilter ancestor_identifier_filter_;
+  std::unique_ptr<IdentifierFilter> ancestor_identifier_filter_;
 };
 
 template <unsigned maximumIdentifierCount>
 inline bool SelectorFilter::FastRejectSelector(
     const unsigned* identifier_hashes) const {
+  DCHECK(ancestor_identifier_filter_);
   for (unsigned n = 0; n < maximumIdentifierCount && identifier_hashes[n];
        ++n) {
-    if (!ancestor_identifier_filter_.MayContain(identifier_hashes[n]))
+    if (!ancestor_identifier_filter_->MayContain(identifier_hashes[n]))
       return true;
   }
   return false;