From c8bb2371ebf25ab78abde84e3c5742f9844a74b7 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Thu, 23 Jul 2015 23:11:08 +0200
Subject: Optimize empty sets

This reduces the number of Bindings allocations by about 10%.
---
 src/libexpr/attr-set.cc | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

(limited to 'src/libexpr/attr-set.cc')

diff --git a/src/libexpr/attr-set.cc b/src/libexpr/attr-set.cc
index 9ac5e603199a..910428c02686 100644
--- a/src/libexpr/attr-set.cc
+++ b/src/libexpr/attr-set.cc
@@ -29,13 +29,17 @@ Bindings * EvalState::allocBindings(Bindings::size_t capacity)
 }
 
 
-void EvalState::mkAttrs(Value & v, unsigned int expected)
+void EvalState::mkAttrs(Value & v, unsigned int capacity)
 {
+    if (capacity == 0) {
+        v = vEmptySet;
+        return;
+    }
     clearValue(v);
     v.type = tAttrs;
-    v.attrs = allocBindings(expected);
+    v.attrs = allocBindings(capacity);
     nrAttrsets++;
-    nrAttrsInAttrsets += expected;
+    nrAttrsInAttrsets += capacity;
 }
 
 
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cgit 1.4.1