From ef3ee55d4216137ae87da314343e0e5e22d90b96 Mon Sep 17 00:00:00 2001
From: EvilSpirit <anandamide@mail.ru>
Date: Wed, 14 Oct 2015 22:26:19 +0600
Subject: [PATCH] Optimize Expr::From(double) by statically allocating common
 constants.

---
 src/expr.cpp | 29 +++++++++++++++++++++++++++++
 src/expr.h   |  3 +++
 2 files changed, 32 insertions(+)

diff --git a/src/expr.cpp b/src/expr.cpp
index 8d6600d5..add6c8b4 100644
--- a/src/expr.cpp
+++ b/src/expr.cpp
@@ -219,6 +219,35 @@ Expr *Expr::From(hParam p) {
 }
 
 Expr *Expr::From(double v) {
+    // Statically allocate common constants.
+    // Note: this is only valid because AllocExpr() uses AllocTemporary(),
+    // and Expr* is never explicitly freed.
+
+    if(v == 0.0) {
+        static Expr zero(0.0);
+        return &zero;
+    }
+
+    if(v == 1.0) {
+        static Expr one(1.0);
+        return &one;
+    }
+
+    if(v == -1.0) {
+        static Expr mone(-1.0);
+        return &mone;
+    }
+
+    if(v == 0.5) {
+        static Expr half(0.5);
+        return &half;
+    }
+
+    if(v == -0.5) {
+        static Expr mhalf(-0.5);
+        return &mhalf;
+    }
+
     Expr *r = AllocExpr();
     r->op = CONSTANT;
     r->x.v = v;
diff --git a/src/expr.h b/src/expr.h
index 30f7b266..d53b0b28 100644
--- a/src/expr.h
+++ b/src/expr.h
@@ -63,6 +63,9 @@ public:
         char    c;
     }       x;
 
+    Expr() { }
+    Expr(double v) : op(CONSTANT) { x.v = v; }
+    
     static inline Expr *AllocExpr(void)
         { return (Expr *)AllocTemporary(sizeof(Expr)); }