From 6f05b70b5f68a54657d2e2e52e9e363056b3e574 Mon Sep 17 00:00:00 2001
From: Tobias Doerffel <tobias.doerffel@gmail.com>
Date: Sun, 3 Aug 2008 13:19:13 +0000
Subject: [PATCH] made oscillator-phase always being positive which allows
 further optimizations of fraction()-method

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@1431 0778d3d1-df1d-0410-868b-ea421aaaa00d
---
 ChangeLog               |  7 ++++++
 include/lmms_math.h     | 54 ++++++++++++++++++++++++++++++++++++++---
 src/core/oscillator.cpp |  3 ++-
 3 files changed, 59 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index bf9bbb082..532e8b00f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2008-08-03	Tobias Doerffel	<tobydox/at/users/dot/sourceforge/dot/net>
+
+	* include/lmms_math.h:
+	* src/core/oscillator.cpp:
+	made oscillator-phase always being positive which allows further
+	optimizations of fraction()-method
+
 2008-08-01	Tobias Doerffel	<tobydox/at/users/dot/sourceforge/dot/net>
 
 	* include/visualization_widget.h:
diff --git a/include/lmms_math.h b/include/lmms_math.h
index 108a8d7eb..9eac3c94f 100644
--- a/include/lmms_math.h
+++ b/include/lmms_math.h
@@ -31,21 +31,67 @@
 
 #include <math.h>
 
-// Equivalent to _x - floorf( _x )
-static inline float fraction( const float _x )
+static inline float absFraction( const float _x )
 {
 	return( _x - ( _x >= 0.0f ? floorf( _x ) : floorf( _x ) - 1 ) );
 }
 
+static inline float fraction( const float _x )
+{
+	return( _x - floorf( _x ) );
+}
+
 #else
 
-// Equivalent to _x - floorf( _x )
-static inline float fraction( const float _x )
+static inline float absFraction( const float _x )
 {
 	return( _x - ( _x >= 0.0f ? static_cast<int>( _x ) :
 						static_cast<int>( _x ) - 1 ) );
 }
 
+static inline float fraction( const float _x )
+{
+	return( _x - static_cast<int>( _x ) );
+}
+
+
+#if 0
+// SSE3-version
+static inline float absFraction( float _x )
+{
+	unsigned int tmp;
+	asm(
+		"fld %%st\n\t"
+		"fisttp %1\n\t"
+		"fild %1\n\t"
+		"ftst\n\t"
+		"sahf\n\t"
+		"jae 1f\n\t"
+		"fld1\n\t"
+		"fsubrp %%st, %%st(1)\n\t"
+	"1:\n\t"
+		"fsubrp %%st, %%st(1)"
+		: "+t"( _x ), "=m"( tmp )
+		:
+		: "st(1)", "cc" );
+	return( _x );
+}
+
+static inline float absFraction( float _x )
+{
+	unsigned int tmp;
+	asm(
+		"fld %%st\n\t"
+		"fisttp %1\n\t"
+		"fild %1\n\t"
+		"fsubrp %%st, %%st(1)"
+		: "+t"( _x ), "=m"( tmp )
+		:
+		: "st(1)" );
+	return( _x );
+}
+#endif
+
 #endif
 
 
diff --git a/src/core/oscillator.cpp b/src/core/oscillator.cpp
index 779a40991..b0902c869 100644
--- a/src/core/oscillator.cpp
+++ b/src/core/oscillator.cpp
@@ -317,7 +317,8 @@ inline void oscillator::recalcPhase( void )
 		m_phaseOffset = m_ext_phaseOffset;
 		m_phase += m_phaseOffset;
 	}
-	m_phase = fraction( m_phase );
+	m_phase = absFraction( m_phase )+2;	// make sure we're not running
+						// negative when doing PM
 }