From a5ad974bec932c63ddc647c9986a513ae32ef663 Mon Sep 17 00:00:00 2001
From: Aleksey Shipilev <shade@openjdk.org>
Date: Mon, 28 Oct 2024 12:11:51 +0000
Subject: [PATCH] 8343056: C2: Micro-optimize Node lists grow

Reviewed-by: kvn, redestad
---
 src/hotspot/share/libadt/vectset.cpp |  8 ++------
 src/hotspot/share/libadt/vectset.hpp | 11 +++++++++--
 src/hotspot/share/opto/node.cpp      |  4 +---
 src/hotspot/share/opto/node.hpp      | 11 +++++++++--
 4 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/src/hotspot/share/libadt/vectset.cpp b/src/hotspot/share/libadt/vectset.cpp
index b0d5d100400..e2eb08b1a34 100644
--- a/src/hotspot/share/libadt/vectset.cpp
+++ b/src/hotspot/share/libadt/vectset.cpp
@@ -49,9 +49,7 @@ void VectorSet::init(Arena* arena) {
 // Expand the existing set to a bigger size
 void VectorSet::grow(uint new_word_capacity) {
   _nesting.check(_set_arena); // Check if a potential reallocation in the arena is safe
-  if (new_word_capacity < _size) {
-    return; // No need to grow
-  }
+  assert(new_word_capacity >= _size, "Should have been checked before, use maybe_grow?");
   assert(new_word_capacity < (1U << 30), "");
   uint x = next_power_of_2(new_word_capacity);
   if (x > _data_size) {
@@ -66,9 +64,7 @@ void VectorSet::grow(uint new_word_capacity) {
 void VectorSet::insert(uint elem) {
   uint32_t word = elem >> word_bits;
   uint32_t mask = 1U << (elem & bit_mask);
-  if (word >= _size) {
-    grow(word);
-  }
+  maybe_grow(word);
   _data[word] |= mask;
 }
 
diff --git a/src/hotspot/share/libadt/vectset.hpp b/src/hotspot/share/libadt/vectset.hpp
index eafa60db1fe..fee15566f24 100644
--- a/src/hotspot/share/libadt/vectset.hpp
+++ b/src/hotspot/share/libadt/vectset.hpp
@@ -49,8 +49,15 @@ private:
   ReallocMark _nesting; // Safety checks for arena reallocation
 
   void init(Arena* arena);
+
   // Grow vector to required word capacity
+  void maybe_grow(uint new_word_capacity) {
+    if (new_word_capacity >= _size) {
+      grow(new_word_capacity);
+    }
+  }
   void grow(uint new_word_capacity);
+
 public:
   VectorSet();
   VectorSet(Arena* arena);
@@ -78,7 +85,7 @@ public:
   //
   bool test_set(uint elem) {
     uint32_t word = elem >> word_bits;
-    grow(word);
+    maybe_grow(word);
     uint32_t mask = 1U << (elem & bit_mask);
     uint32_t data = _data[word];
     _data[word] = data | mask;
@@ -107,7 +114,7 @@ public:
   // Fast inlined set
   void set(uint elem) {
     uint32_t word = elem >> word_bits;
-    grow(word);
+    maybe_grow(word);
     uint32_t mask = 1U << (elem & bit_mask);
     _data[word] |= mask;
   }
diff --git a/src/hotspot/share/opto/node.cpp b/src/hotspot/share/opto/node.cpp
index 8dbf09f7d4f..3f82c472163 100644
--- a/src/hotspot/share/opto/node.cpp
+++ b/src/hotspot/share/opto/node.cpp
@@ -2770,9 +2770,7 @@ const RegMask &Node::in_RegMask(uint) const {
 
 void Node_Array::grow(uint i) {
   _nesting.check(_a); // Check if a potential reallocation in the arena is safe
-  if (i < _max) {
-    return; // No need to grow
-  }
+  assert(i >= _max, "Should have been checked before, use maybe_grow?");
   assert(_max > 0, "invariant");
   uint old = _max;
   _max = next_power_of_2(i);
diff --git a/src/hotspot/share/opto/node.hpp b/src/hotspot/share/opto/node.hpp
index 0afb3c9166b..821e1aa38a7 100644
--- a/src/hotspot/share/opto/node.hpp
+++ b/src/hotspot/share/opto/node.hpp
@@ -1610,7 +1610,14 @@ protected:
   Node** _nodes;
   ReallocMark _nesting;         // Safety checks for arena reallocation
 
-  void   grow( uint i );        // Grow array node to fit
+  // Grow array to required capacity
+  void maybe_grow(uint i) {
+    if (i >= _max) {
+      grow(i);
+    }
+  }
+  void grow(uint i);
+
 public:
   Node_Array(Arena* a, uint max = OptoNodeListSize) : _a(a), _max(max) {
     _nodes = NEW_ARENA_ARRAY(a, Node*, max);
@@ -1628,7 +1635,7 @@ public:
   Node* at(uint i) const { assert(i<_max,"oob"); return _nodes[i]; }
   Node** adr() { return _nodes; }
   // Extend the mapping: index i maps to Node *n.
-  void map( uint i, Node *n ) { grow(i); _nodes[i] = n; }
+  void map( uint i, Node *n ) { maybe_grow(i); _nodes[i] = n; }
   void insert( uint i, Node *n );
   void remove( uint i );        // Remove, preserving order
   // Clear all entries in _nodes to null but keep storage