From: Jean Privat <jean@pryen.org>
Date: Tue, 3 Mar 2015 15:05:33 +0000 (+0700)
Subject: Merge: compiler: fast path is the hot path in once and literal strings
X-Git-Tag: v0.7.3~42
X-Git-Url: http://nitlanguage.org?hp=bac6a950e3c79f5fd9a65be26c3119a4fe3ee6ae

Merge: compiler: fast path is the hot path in once and literal strings

`once` structure and literal strings are implemented with a guard so that
onced-expression and literal strings are evaluated/created once then
stored in a static variable.

This patch just informs GCC that the fast path (get the saved value)
it the frequent path. It's up to GCC to do something useful with this
information.

It seems it does since number for nitc/nitc/nitc are

before: 0m7.324s
after: 0m7.156s (-2.3%)

Pull-Request: #1183
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
---

diff --git a/src/compiler/abstract_compiler.nit b/src/compiler/abstract_compiler.nit
index 01de936..b53a7a2 100644
--- a/src/compiler/abstract_compiler.nit
+++ b/src/compiler/abstract_compiler.nit
@@ -1443,7 +1443,7 @@ abstract class AbstractCompilerVisitor
 		var name = self.get_name("varonce")
 		self.add_decl("static {mtype.ctype} {name};")
 		var res = self.new_var(mtype)
-		self.add("if ({name}) \{")
+		self.add("if (likely({name}!=NULL)) \{")
 		self.add("{res} = {name};")
 		self.add("\} else \{")
 		var native_mtype = self.get_class("NativeString").mclass_type
@@ -2823,7 +2823,7 @@ redef class AOnceExpr
 		v.add_decl("static {mtype.ctype} {name};")
 		v.add_decl("static int {guard};")
 		var res = v.new_var(mtype)
-		v.add("if ({guard}) \{")
+		v.add("if (likely({guard})) \{")
 		v.add("{res} = {name};")
 		v.add("\} else \{")
 		var i = v.expr(self.n_expr, mtype)