From 950a84c337f317388cf39a3820125e049c598b8d Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 18 Apr 2022 14:39:13 +0200
Subject: Optimize header cache some more by storing hash in key

---
 libbuild2/cc/compile-rule.cxx | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

(limited to 'libbuild2/cc/compile-rule.cxx')

diff --git a/libbuild2/cc/compile-rule.cxx b/libbuild2/cc/compile-rule.cxx
index 2faa711..c72c94c 100644
--- a/libbuild2/cc/compile-rule.cxx
+++ b/libbuild2/cc/compile-rule.cxx
@@ -2906,7 +2906,10 @@ namespace build2
 
       // First check the cache.
       //
-      if (fp.absolute ())
+      config_module::header_key hk;
+
+      bool e (fp.absolute ());
+      if (e)
       {
         if (!norm)
         {
@@ -2914,14 +2917,19 @@ namespace build2
           norm = true;
         }
 
+        hk.file = move (fp);
+        hk.hash = hash<path> () (hk.file);
+
         slock l (hc.header_map_mutex);
-        auto i (hc.header_map.find (fp));
+        auto i (hc.header_map.find (hk));
         if (i != hc.header_map.end ())
         {
           //cache_hit.fetch_add (1, memory_order_relaxed);
           return make_pair (i->second, false);
         }
 
+        fp = move (hk.file);
+
         //cache_mis.fetch_add (1, memory_order_relaxed);
       }
 
@@ -2957,10 +2965,18 @@ namespace build2
       //
       if (r.first != nullptr)
       {
+        hk.file = move (fp);
+
+        // Calculate the hash if we haven't yet and re-calculate it if the
+        // path has changed (header has been remapped).
+        //
+        if (!e || r.second)
+          hk.hash = hash<path> () (hk.file);
+
         const file* f;
         {
           ulock l (hc.header_map_mutex);
-          auto p (hc.header_map.emplace (move (fp), r.first));
+          auto p (hc.header_map.emplace (move (hk), r.first));
           f = p.second ? nullptr : p.first->second;
         }
 
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