Add ScopedDenormalDisable class, use it in standalone native audio

Signed-off-by: falkTX <falktx@falktx.com>

distrho/extra/ScopedDenormalDisable.hpp

@@ -0,0 +1,112 @@
+/*
+ * DISTRHO Plugin Framework (DPF)
+ * Copyright (C) 2012-2023 Filipe Coelho <falktx@falktx.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any purpose with
+ * or without fee is hereby granted, provided that the above copyright notice and this
+ * permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
+ * TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN
+ * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef DISTRHO_SCOPED_DENORMAL_DISABLE_HPP_INCLUDED
+#define DISTRHO_SCOPED_DENORMAL_DISABLE_HPP_INCLUDED
+
+#include "../DistrhoUtils.hpp"
+
+#ifdef __SSE2_MATH__
+# include <xmmintrin.h>
+#endif
+
+START_NAMESPACE_DISTRHO
+
+// --------------------------------------------------------------------------------------------------------------------
+// ScopedDenormalDisable class definition
+
+/**
+   ScopedDenormalDisable is a handy class for disabling denormal numbers during a function scope.
+   Denormal numbers can happen in IIR or other types of filters, they are often very slow.
+
+   Use this class with care! Messing up with the global state is bound to make some hosts unhappy.
+ */
+class ScopedDenormalDisable {
+public:
+    /*
+     * Constructor.
+     * Current cpu flags will saved, then denormals-as-zero and flush-to-zero set on top.
+     */
+    inline ScopedDenormalDisable() noexcept;
+
+    /*
+     * Destructor.
+     * CPU flags will be restored to the value obtained in the constructor.
+     */
+    inline ~ScopedDenormalDisable() noexcept
+    {
+        setFlags(oldflags);
+    }
+
+private:
+   #if defined(__SSE2_MATH__)
+    typedef uint cpuflags_t;
+   #elif defined(__aarch64__)
+    typedef uint64_t cpuflags_t;
+   #elif defined(__arm__) && !defined(__SOFTFP__)
+    typedef uint32_t cpuflags_t;
+   #else
+    typedef char cpuflags_t;
+   #endif
+
+    // retrieved on constructor, reset to it on destructor
+    cpuflags_t oldflags;
+
+    // helper function to set cpu flags
+    inline void setFlags(cpuflags_t flags) noexcept;
+
+    DISTRHO_DECLARE_NON_COPYABLE(ScopedDenormalDisable)
+    DISTRHO_PREVENT_HEAP_ALLOCATION
+};
+
+// --------------------------------------------------------------------------------------------------------------------
+// ScopedDenormalDisable class implementation
+
+inline ScopedDenormalDisable::ScopedDenormalDisable() noexcept
+    : oldflags(0)
+{
+   #if defined(__SSE2_MATH__)
+    oldflags = _mm_getcsr();
+    setFlags(oldflags | 0x8040);
+   #elif defined(__aarch64__)
+    __asm__ __volatile__("mrs %0, fpcr" : "=r" (oldflags));
+    setFlags(oldflags | 0x1000000);
+    __asm__ __volatile__("isb");
+   #elif defined(__arm__) && !defined(__SOFTFP__)
+    __asm__ __volatile__("vmrs %0, fpscr" : "=r" (oldflags));
+    setFlags(oldflags | 0x1000000);
+   #endif
+}
+
+inline void ScopedDenormalDisable::setFlags(const cpuflags_t flags) noexcept
+{
+   #if defined(__SSE2_MATH__)
+    _mm_setcsr(flags);
+   #elif defined(__aarch64__)
+    __asm__ __volatile__("msr fpcr, %0" :: "r" (flags));
+   #elif defined(__arm__) && !defined(__SOFTFP__)
+    __asm__ __volatile__("vmsr fpscr, %0" :: "r" (flags));
+   #else
+    // unused
+    (void)flags;
+   #endif
+}
+
+// --------------------------------------------------------------------------------------------------------------------
+
+END_NAMESPACE_DISTRHO
+
+#endif // DISTRHO_SCOPED_DENORMAL_DISABLE_HPP_INCLUDED

distrho/src/jackbridge/RtAudioBridge.hpp

@@ -50,6 +50,7 @@
 # include "rtmidi/RtMidi.h"
 # include "../../extra/ScopedPointer.hpp"
 # include "../../extra/String.hpp"
+# include "../../extra/ScopedDenormalDisable.hpp"
 
 using DISTRHO_NAMESPACE::ScopedPointer;
 using DISTRHO_NAMESPACE::String;
@@ -377,6 +378,7 @@ struct RtAudioBridge : NativeBridge {
         }
        #endif
 
+        const ScopedDenormalDisable sdd;
         self->jackProcessCallback(numFrames, self->jackProcessArg);
 
         return 0;

distrho/src/jackbridge/SDL2Bridge.hpp

@@ -1,6 +1,6 @@
 /*
  * SDL Bridge for DPF
- * Copyright (C) 2021-2022 Filipe Coelho <falktx@falktx.com>
+ * Copyright (C) 2021-2023 Filipe Coelho <falktx@falktx.com>
  *
  * Permission to use, copy, modify, and/or distribute this software for any purpose with
  * or without fee is hereby granted, provided that the above copyright notice and this
@@ -18,6 +18,7 @@
 #define SDL_BRIDGE_HPP_INCLUDED
 
 #include "NativeBridge.hpp"
+#include "../../extra/ScopedDenormalDisable.hpp"
 
 #include <SDL.h>
 
@@ -246,6 +247,7 @@ struct SDL2Bridge : NativeBridge {
         const uint numFrames = static_cast<uint>(len / sizeof(float) / DISTRHO_PLUGIN_NUM_OUTPUTS);
         DISTRHO_SAFE_ASSERT_UINT2_RETURN(numFrames == self->bufferSize, numFrames, self->bufferSize,);
 
+        const ScopedDenormalDisable sdd;
         self->jackProcessCallback(numFrames, self->jackProcessArg);
 
         float* const fstream = (float*)stream;