Clean up dsp headers and documentation.

include/dsp/simd.hpp

@@ -1,27 +1,27 @@
 #include "sse_mathfun.h"
 #include <cstring>
 #include <cmath>
-#include <emmintrin.h>
+#include <x86intrin.h>
 
 
 namespace rack {
 namespace dsp {
 
 
-/** Casts an int to float, bitwise without conversion. */
-inline float cast_i32_f32(int i) {
-	static_assert(sizeof(int) == sizeof(float), "int and float must be the same size");
-	// Should be optimized to two `mov` instructions
-	float f;
-	std::memcpy(&f, &i, sizeof(f));
-	return f;
-}
+/** Casts the literal bits of FROM to TO without type conversion.
+API copied from C++20.
 
+Usage example:
 
-inline int cast_f32_i32(float f) {
-	float i;
-	std::memcpy(&i, &f, sizeof(i));
-	return i;
+	printf("%08x\n", bit_cast<int>(1.f)); // Prints 3f800000
+*/
+template <typename TO, typename FROM>
+TO bit_cast(const FROM &x) {
+	static_assert(sizeof(FROM) == sizeof(TO), "types must have equal size");
+	// Should be optimized to two `mov` instructions
+	TO y;
+	std::memcpy(&y, &x, sizeof(x));
+	return y;
 }
 
 
@@ -30,6 +30,7 @@ inline int cast_f32_i32(float f) {
 This class is designed to be used just like `float` scalars, with extra features for handling bitwise logic, conditions, loading, and storing.
 
 Usage example:
+
 	float a[4], b[4];
 	f32_4 a = f32_4::load(in);
 	f32_4 b = 2.f * a / (1 - a);
@@ -117,9 +118,11 @@ DECLARE_F32_4_OPERATOR_INFIX(operator/, _mm_div_ps)
 
 /**
 Use these to apply logic, bit masks, and conditions to elements.
+
 Examples:
 
 Subtract 1 from value if greater than or equal to 1.
+
 	x -= (x >= 1.f) & 1.f;
 */
 DECLARE_F32_4_OPERATOR_INFIX(operator^, _mm_xor_ps)

include/dsp/window.hpp

@@ -6,7 +6,7 @@ namespace rack {
 namespace dsp {
 
 
-/** Hann window function
+/** Hann window function.
 p: proportion from [0, 1], usually `i / (len - 1)`
 https://en.wikipedia.org/wiki/Window_function#Hann_and_Hamming_windows
 */
@@ -14,14 +14,14 @@ inline float hann(float p) {
 	return 0.5f * (1.f - std::cos(2*M_PI * p));
 }
 
-/** Applies the Hann window to a signal `x` */
+/** Applies the Hann window to a signal `x`. */
 inline void hannWindow(float *x, int len) {
 	for (int i = 0; i < len; i++) {
 		x[i] *= hann((float) i / (len - 1));
 	}
 }
 
-/** Blackman window function
+/** Blackman window function.
 https://en.wikipedia.org/wiki/Window_function#Blackman_window
 A typical alpha value is 0.16.
 */
@@ -39,7 +39,7 @@ inline void blackmanWindow(float alpha, float *x, int len) {
 }
 
 
-/** Blackman-Nuttall window function
+/** Blackman-Nuttall window function.
 https://en.wikipedia.org/wiki/Window_function#Blackman%E2%80%93Nuttall_window
 */
 inline float blackmanNuttall(float p) {
@@ -56,7 +56,7 @@ inline void blackmanNuttallWindow(float *x, int len) {
 	}
 }
 
-/** Blackman-Harris window function
+/** Blackman-Harris window function.
 https://en.wikipedia.org/wiki/Window_function#Blackman%E2%80%93Harris_window
 */
 inline float blackmanHarris(float p) {

include/engine/Port.hpp

@@ -43,7 +43,7 @@ struct alignas(32) Port {
 
 	/** Returns the given channel's voltage if the port is polyphonic, otherwise returns the first voltage (channel 0). */
 	float getPolyVoltage(int channel) {
-		return (channels > 1) ? getVoltage(channel) : getVoltage(0);
+		return (channels == 1) ? getVoltage(0) : getVoltage(channel);
 	}
 
 	/** Returns the voltage if a cable is connected, otherwise returns the given normal voltage. */

include/rack.hpp

@@ -80,6 +80,7 @@
 #include "plugin/callbacks.hpp"
 
 #include "dsp/common.hpp"
+#include "dsp/simd.hpp"
 #include "dsp/digital.hpp"
 #include "dsp/fft.hpp"
 #include "dsp/filter.hpp"