section.hpp

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/**
 * @file section.hpp
 * @brief Per-section cycle profiling with EWMA smoothing
 *
 * Measures CPU cycles consumed by named code sections in audio callbacks.
 * Uses integer EWMA (alpha = 1/128, shift-based) for low-overhead smoothing.
 *
 * Gated behind SBL_PROFILING_ENABLED. When disabled, SectionProfile::avg
 * is a static constexpr zero so format strings compile without #ifdef.
 *
 * Usage:
 *   static sbl::profiling::SectionProfile s_prof_osc;
 *   static sbl::profiling::SectionProfile s_prof_svf;
 *
 *   void audio_callback(...) {
 *       SBL_PROF_MARK(t);
 *       // ... oscillator rendering ...
 *       SBL_PROF_SECTION(s_prof_osc, t);
 *       // ... filter processing ...
 *       SBL_PROF_SECTION(s_prof_svf, t);
 *   }
 */
#pragma once
#include <cstdint>
 
#ifdef SBL_PROFILING_ENABLED
#include <sbl/profiling/dwt.hpp>
#endif
 
namespace sbl::profiling {
 
#ifdef SBL_PROFILING_ENABLED
 
struct SectionProfile {
    uint32_t avg = 0;  // EWMA accumulator (alpha = 1/128)
 
    void update(uint32_t cyc) {
        avg = avg - (avg >> 7) + (cyc >> 7);
    }
};
 
#else
 
struct SectionProfile {
    static constexpr uint32_t avg = 0;
 
    void update(uint32_t) {}
};
 
#endif
 
} // namespace sbl::profiling
 
/// Mark a timestamp variable for section profiling
#ifdef SBL_PROFILING_ENABLED
#define SBL_PROF_MARK(var) uint32_t var = sbl::profiling::cycles()
#else
#define SBL_PROF_MARK(var) (void)0
#endif
 
/// Measure cycles since 'start', update section profile, advance start
#ifdef SBL_PROFILING_ENABLED
#define SBL_PROF_SECTION(section, start) do { \
    uint32_t _end = sbl::profiling::cycles(); \
    section.update(_end - start); \
    start = _end; \
} while(0)
#else
#define SBL_PROF_SECTION(section, start) (void)0
#endif