From 93cc2eef38eab76831916bfee9d6fe16fbaaf4c1 Mon Sep 17 00:00:00 2001
From: Stephen Kelly <steveire@gmail.com>
Date: Sat, 6 Jun 2015 09:41:05 +0200
Subject: [PATCH] cmPolicies: Store all statuses in a single bitset.

Currently there are an optimal number of policies (64) such that
there are no wasted bits.  When another policy is added, the
cmPolicyMap will grow from 40 bytes to 80, and occupy 45.  By storing
all in a single bitset, we stay under the cache line size of 64 bytes
until there are 512 policies in a range.
---
 Source/cmPolicies.cxx | 30 +++++++++++++++++-------------
 Source/cmPolicies.h   |  7 ++-----
 2 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/Source/cmPolicies.cxx b/Source/cmPolicies.cxx
index 3498adc80..5026893ba 100644
--- a/Source/cmPolicies.cxx
+++ b/Source/cmPolicies.cxx
@@ -348,19 +348,19 @@ cmPolicies::PolicyMap::Get(cmPolicies::PolicyID id) const
 {
   PolicyStatus status = cmPolicies::WARN;
 
-  if (this->OLD[id])
+  if (this->Status[(POLICY_STATUS_COUNT * id) + OLD])
     {
     status = cmPolicies::OLD;
     }
-  else if (this->NEW[id])
+  else if (this->Status[(POLICY_STATUS_COUNT * id) + NEW])
     {
     status = cmPolicies::NEW;
     }
-  else if (this->REQUIRED_ALWAYS[id])
+  else if (this->Status[(POLICY_STATUS_COUNT * id) + REQUIRED_ALWAYS])
     {
     status = cmPolicies::REQUIRED_ALWAYS;
     }
-  else if (this->REQUIRED_IF_USED[id])
+  else if (this->Status[(POLICY_STATUS_COUNT * id) + REQUIRED_IF_USED])
     {
     status = cmPolicies::REQUIRED_IF_USED;
     }
@@ -370,21 +370,25 @@ cmPolicies::PolicyMap::Get(cmPolicies::PolicyID id) const
 void cmPolicies::PolicyMap::Set(cmPolicies::PolicyID id,
                                 cmPolicies::PolicyStatus status)
 {
-  this->OLD[id] = (status == cmPolicies::OLD);
-  this->WARN[id] = (status == cmPolicies::WARN);
-  this->NEW[id] = (status == cmPolicies::NEW);
-  this->REQUIRED_ALWAYS[id] = (status == cmPolicies::REQUIRED_ALWAYS);
-  this->REQUIRED_IF_USED[id] = (status == cmPolicies::REQUIRED_IF_USED);
+  this->Status[(POLICY_STATUS_COUNT * id) + OLD] = (status == OLD);
+  this->Status[(POLICY_STATUS_COUNT * id) + WARN] = (status == WARN);
+  this->Status[(POLICY_STATUS_COUNT * id) + NEW] = (status == NEW);
+  this->Status[(POLICY_STATUS_COUNT * id) + REQUIRED_ALWAYS] =
+      (status == REQUIRED_ALWAYS);
+  this->Status[(POLICY_STATUS_COUNT * id) + REQUIRED_IF_USED] =
+      (status == REQUIRED_IF_USED);
 }
 
 bool cmPolicies::PolicyMap::IsDefined(cmPolicies::PolicyID id) const
 {
-  return this->OLD[id] || this->WARN[id] || this->NEW[id]
-      || this->REQUIRED_ALWAYS[id] || this->REQUIRED_IF_USED[id];
+  return this->Status[(POLICY_STATUS_COUNT * id) + OLD]
+      || this->Status[(POLICY_STATUS_COUNT * id) + WARN]
+      || this->Status[(POLICY_STATUS_COUNT * id) + NEW]
+      || this->Status[(POLICY_STATUS_COUNT * id) + REQUIRED_ALWAYS]
+      || this->Status[(POLICY_STATUS_COUNT * id) + REQUIRED_IF_USED];
 }
 
 bool cmPolicies::PolicyMap::IsEmpty() const
 {
-  return this->OLD.none() && this->WARN.none() && this->NEW.none()
-      && this->REQUIRED_ALWAYS.none() && this->REQUIRED_IF_USED.none();
+  return this->Status.none();
 }
diff --git a/Source/cmPolicies.h b/Source/cmPolicies.h
index 8c72dfe4a..8a3c27d9f 100644
--- a/Source/cmPolicies.h
+++ b/Source/cmPolicies.h
@@ -244,6 +244,7 @@ public:
     REQUIRED_IF_USED,
     REQUIRED_ALWAYS ///< Issue an error unless user sets policy status to NEW.
   };
+#define POLICY_STATUS_COUNT 5
 
   /// Policy identifiers
   enum PolicyID
@@ -287,11 +288,7 @@ public:
     bool IsEmpty() const;
 
   private:
-    std::bitset<cmPolicies::CMPCOUNT> OLD;
-    std::bitset<cmPolicies::CMPCOUNT> WARN;
-    std::bitset<cmPolicies::CMPCOUNT> NEW;
-    std::bitset<cmPolicies::CMPCOUNT> REQUIRED_IF_USED;
-    std::bitset<cmPolicies::CMPCOUNT> REQUIRED_ALWAYS;
+    std::bitset<cmPolicies::CMPCOUNT * POLICY_STATUS_COUNT> Status;
   };
 };