From 2290f05dcb698cbede085807091c365d99c462eb Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Mon, 7 Nov 2022 10:36:34 +0100
Subject: [PATCH] Revert "- Use `std::fma()` in the interpolation code."

This reverts commit ff7e0afa6fdbb93f1c8ac5ab465a40e85b8edd41.

On Visual Studio with precise math, which is our main target this generates a very expensive function call instead of optimized assembly which renders the function's purpose ad absurdum.
---
 source/common/utility/vectors.h | 24 ++++++------------------
 1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/source/common/utility/vectors.h b/source/common/utility/vectors.h
index 5f619923a..019eb9db1 100644
--- a/source/common/utility/vectors.h
+++ b/source/common/utility/vectors.h
@@ -41,7 +41,7 @@
 #define VECTORS_H
 
 #include <cstddef>
-#include <cmath>
+#include <math.h>
 #include <float.h>
 #include <string.h>
 #include "xs_Float.h"
@@ -1548,27 +1548,15 @@ inline TVector2<T> clamp(const TVector2<T> &vec, const TVector2<T> &min, const T
 }
 
 template<class T>
-inline T interpolatedvalue(const T oval, const T val, const double interpfrac)
+inline TAngle<T> interpolatedvalue(const TAngle<T> &oang, const TAngle<T> &ang, const double interpfrac)
 {
-	return std::fma(interpfrac, val, std::fma(-interpfrac, oval, oval));
+	return oang + (deltaangle(oang, ang) * interpfrac);
 }
 
-template<class T>
-inline TVector2<T> interpolatedvalue(const TVector2<T>& oval, const TVector2<T>& val, const double interpfrac)
+template <class T>
+inline T interpolatedvalue(const T& oval, const T& val, const double interpfrac)
 {
-	return { interpolatedvalue(oval.X, val.X, interpfrac), interpolatedvalue(oval.Y, val.Y, interpfrac) };
-}
-
-template<class T>
-inline TVector3<T> interpolatedvalue(const TVector3<T>& oval, const TVector3<T>& val, const double interpfrac)
-{
-	return { interpolatedvalue(oval.X, val.X, interpfrac), interpolatedvalue(oval.Y, val.Y, interpfrac), interpolatedvalue(oval.Z, val.Z, interpfrac) };
-}
-
-template<class T>
-inline TAngle<T> interpolatedvalue(const TAngle<T> oang, const TAngle<T> ang, const double interpfrac)
-{
-	return TAngle<T>::fromDeg(interpolatedvalue(oang.Degrees(), (oang + deltaangle(oang, ang)).Degrees(), interpfrac));
+	return T(oval + (val - oval) * interpfrac);
 }
 
 // Much of this is copied from TVector3. Is all that functionality really appropriate?