Optimise usage of pow using fast equivalent and exp2 (#7548)

* replace std::pow with better performing equivalents

* revert one instance where I swapped to fastPow10f

* Negative slope instead of multiplying -1

Co-authored-by: saker <sakertooth@gmail.com>

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Co-authored-by: saker <sakertooth@gmail.com>

plugins/FreeBoy/FreeBoy.cpp

@@ -352,14 +352,14 @@ void FreeBoyInstrument::playNote(NotePlayHandle* nph, SampleFrame* workingBuffer
 		// a unique frequency, we can start by guessing s = r = 0 here and then skip r = 0 in the loop.
 		char clock_freq = 0;
 		char div_ratio = 0;
-		float closest_freq = 524288.0 / (0.5 * std::pow(2.0, clock_freq + 1.0));
+		float closest_freq = 524288.0 / (0.5 * std::exp2(clock_freq + 1.0));
 		// This nested for loop iterates over all possible combinations of clock frequency and dividing
 		// ratio and chooses the combination whose resulting frequency is closest to the note frequency
 		for (char s = 0; s < 16; ++s)
 		{
 			for (char r = 1; r < 8; ++r)
 			{
-				float f = 524288.0 / (r * std::pow(2.0, s + 1.0));
+				float f = 524288.0 / (r * std::exp2(s + 1.0));
 				if (std::fabs(freq - closest_freq) > std::fabs(freq - f))
 				{
 					closest_freq = f;

plugins/Monstro/Monstro.cpp

@@ -1462,14 +1462,14 @@ void MonstroInstrument::updateSamplerate()
 void MonstroInstrument::updateSlope1()
 {
 	const float slope = m_env1Slope.value();
-	m_slope[0] = std::pow(10.f, slope * -1.0f );
+	m_slope[0] = fastPow10f(-slope);
 }
 
 
 void MonstroInstrument::updateSlope2()
 {
 	const float slope = m_env2Slope.value();
-	m_slope[1] = std::pow(10.f, slope * -1.0f );
+	m_slope[1] = fastPow10f(-slope);
 }
 
 

plugins/MultitapEcho/MultitapEchoControls.cpp

@@ -147,7 +147,7 @@ void MultitapEchoControls::lpSamplesChanged( int begin, int end )
 	const float * samples = m_lpGraph.samples();
 	for( int i = begin; i <= end; ++i )
 	{
-		m_effect->m_lpFreq[i] = 20.0f * std::pow(10.f, samples[i] );
+		m_effect->m_lpFreq[i] = 20.0f * fastPow10f(samples[i]);
 	}
 	m_effect->updateFilters( begin, end );
 }

plugins/SlicerT/SlicerT.cpp

@@ -214,7 +214,7 @@ void SlicerT::findSlices()
 			float magnitude = std::sqrt(real * real + imag * imag);
 
 			// using L2-norm (euclidean distance)
-			float diff = std::sqrt(std::pow(magnitude - prevMags[j], 2));
+			float diff = std::abs(magnitude - prevMags[j]);
 			spectralFlux += diff;
 
 			prevMags[j] = magnitude;