Improved performance of loop.

Author: dok-net

cores/esp8266/core_esp8266_waveform.cpp

@@ -91,11 +91,6 @@ namespace {
 
     bool timer1Running = false;
 
-    // Optimize the NMI inner loop by keeping track of the min and max GPIO that we
-    // are generating.  In the common case (1 PWM) these may be the same pin and
-    // we can avoid looking at the other pins.
-    int startPin = 0;
-    int endPin = 0;
     uint32_t nextEventCcy;
   } waveform;
 
@@ -266,9 +261,6 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {
     // Handle enable/disable requests from main app.
     waveform.enabled = (waveform.enabled & ~waveform.toDisableBits) | waveform.toSetBits; // Set the requested waveforms on/off
     // Find the first GPIO being generated by checking GCC's find-first-set (returns 1 + the bit of the first 1 in an int32_t)
-    waveform.startPin = __builtin_ffs(waveform.enabled) - 1;
-    // Find the last bit by subtracting off GCC's count-leading-zeros (no offset in this one)
-    waveform.endPin = 32 - __builtin_clz(waveform.enabled);
     waveform.toDisableBits = 0;
   }
 
@@ -319,11 +311,11 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {
       break;
     }
     isrNextEventCcy = waveform.nextEventCcy;
-    for (int pin = waveform.startPin; pin <= waveform.endPin; ++pin) {
+    uint32_t loopPins = busyPins;
+    while (loopPins) {
+      const int pin = __builtin_ffsl(loopPins) - 1;
       const uint32_t pinBit = 1UL << pin;
-      // If it's not on, ignore
-      if (!(busyPins & pinBit))
-        continue;
+      loopPins ^= pinBit;
 
       Waveform& wave = waveform.pins[pin];