From ab654af0e29e5eb6eab7289d05699b45417d1f68 Mon Sep 17 00:00:00 2001
From: Etienne Noreau-Hebert <etienne@korg.co.jp>
Date: Wed, 17 Jun 2020 13:46:10 +0900
Subject: [PATCH] [nutekt/minilogue-xd/prologue] Fixes and performance
 improvements for float_math.h

---
 platform/minilogue-xd/inc/utils/float_math.h   | 9 +++++----
 platform/nutekt-digital/inc/utils/float_math.h | 9 +++++----
 platform/prologue/inc/utils/float_math.h       | 9 +++++----
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/platform/minilogue-xd/inc/utils/float_math.h b/platform/minilogue-xd/inc/utils/float_math.h
index 1d97db85..97b4e7dc 100644
--- a/platform/minilogue-xd/inc/utils/float_math.h
+++ b/platform/minilogue-xd/inc/utils/float_math.h
@@ -661,7 +661,7 @@ float fasterlog2f(float x) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fastlogf(float x) {
-  return 0.69314718f * fastlog2f(x);
+  return M_LN2 * fastlog2f(x);
 }
 
 /** "Fast" natural logarithm approximation, valid for positive x as precision allows.
@@ -669,7 +669,7 @@ float fastlogf(float x) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterlogf(float x) {
-  return 0.69314718f * fasterlog2f(x);
+  return M_LN2 * fasterlog2f(x);
 }
 
 /** "Fast" power of 2 approximation, valid for x in [ -126, ... as precision allows.
@@ -789,7 +789,8 @@ float ampdbf(const float amp) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterampdbf(const float amp) {
-  return 20.f*fasterlog2f(amp)/fasterlog2f(10);
+  static const float c = 3.3219280948873626f; // 20.f / log2f(10);
+  return c*fasterlog2f(amp);
 }
 
 /** dB to ampltitude
@@ -803,7 +804,7 @@ float dbampf(const float db) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterdbampf(const float db) {
-  return 20.f*fasterpowf(10.f, 0.05f*db);
+  return fasterpowf(10.f, 0.05f*db);
 }
 
 /** @} */
diff --git a/platform/nutekt-digital/inc/utils/float_math.h b/platform/nutekt-digital/inc/utils/float_math.h
index 1d97db85..97b4e7dc 100644
--- a/platform/nutekt-digital/inc/utils/float_math.h
+++ b/platform/nutekt-digital/inc/utils/float_math.h
@@ -661,7 +661,7 @@ float fasterlog2f(float x) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fastlogf(float x) {
-  return 0.69314718f * fastlog2f(x);
+  return M_LN2 * fastlog2f(x);
 }
 
 /** "Fast" natural logarithm approximation, valid for positive x as precision allows.
@@ -669,7 +669,7 @@ float fastlogf(float x) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterlogf(float x) {
-  return 0.69314718f * fasterlog2f(x);
+  return M_LN2 * fasterlog2f(x);
 }
 
 /** "Fast" power of 2 approximation, valid for x in [ -126, ... as precision allows.
@@ -789,7 +789,8 @@ float ampdbf(const float amp) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterampdbf(const float amp) {
-  return 20.f*fasterlog2f(amp)/fasterlog2f(10);
+  static const float c = 3.3219280948873626f; // 20.f / log2f(10);
+  return c*fasterlog2f(amp);
 }
 
 /** dB to ampltitude
@@ -803,7 +804,7 @@ float dbampf(const float db) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterdbampf(const float db) {
-  return 20.f*fasterpowf(10.f, 0.05f*db);
+  return fasterpowf(10.f, 0.05f*db);
 }
 
 /** @} */
diff --git a/platform/prologue/inc/utils/float_math.h b/platform/prologue/inc/utils/float_math.h
index 1d97db85..97b4e7dc 100644
--- a/platform/prologue/inc/utils/float_math.h
+++ b/platform/prologue/inc/utils/float_math.h
@@ -661,7 +661,7 @@ float fasterlog2f(float x) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fastlogf(float x) {
-  return 0.69314718f * fastlog2f(x);
+  return M_LN2 * fastlog2f(x);
 }
 
 /** "Fast" natural logarithm approximation, valid for positive x as precision allows.
@@ -669,7 +669,7 @@ float fastlogf(float x) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterlogf(float x) {
-  return 0.69314718f * fasterlog2f(x);
+  return M_LN2 * fasterlog2f(x);
 }
 
 /** "Fast" power of 2 approximation, valid for x in [ -126, ... as precision allows.
@@ -789,7 +789,8 @@ float ampdbf(const float amp) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterampdbf(const float amp) {
-  return 20.f*fasterlog2f(amp)/fasterlog2f(10);
+  static const float c = 3.3219280948873626f; // 20.f / log2f(10);
+  return c*fasterlog2f(amp);
 }
 
 /** dB to ampltitude
@@ -803,7 +804,7 @@ float dbampf(const float db) {
  */
 static inline __attribute__((optimize("Ofast"), always_inline))
 float fasterdbampf(const float db) {
-  return 20.f*fasterpowf(10.f, 0.05f*db);
+  return fasterpowf(10.f, 0.05f*db);
 }
 
 /** @} */