Handle rate = 0 in SC enveloep better (#141)

With the new exp shape, rate = 0 means really 0. This
means we get infs in the dPhase (which is bad) if not careful
but also means we need to skip phases more consicously, so do that
here.

include/sst/basic-blocks/modulators/AHDSRShapedSC.h

@@ -104,6 +104,9 @@ struct AHDSRShapedSC : DiscreteStagesEnvelope<BLOCK_SIZE, RangeProvider>
 
         if constexpr (RangeProvider::phaseStrategy == ENVTIME_EXP)
         {
+            if (x == 0.0)
+                return 1.0;
+
             static thread_local tables::TwoToTheXProvider twoToX;
             if (!twoToX.isInit)
                 twoToX.init();
@@ -126,9 +129,19 @@ struct AHDSRShapedSC : DiscreteStagesEnvelope<BLOCK_SIZE, RangeProvider>
             static float lastX = -23;
             if (x != lastX)
             {
-                std::cout << "Checkint at " << x << " " << checkV << " " << res << std::endl;
+                std::cout << "Checkint at x=" << x << "\n  calc=" << checkV << " lut=" << res
+                          << "\n  time=" << timeInSeconds << "\n  sr=" << srProvider->sampleRate
+                          << " sri=" << srProvider->sampleRateInv
+                          << " 1/sri=" << 1.0 / srProvider->sampleRateInv << " bs=" << BLOCK_SIZE
+                          << "\n  dPhaseLUT=" << BLOCK_SIZE * srProvider->sampleRateInv * res
+                          << "\n  dPhaseCAL=" << BLOCK_SIZE * srProvider->sampleRateInv * checkV
+                          << "\n  1/dPhaseLUT="
+                          << 1 / (BLOCK_SIZE * srProvider->sampleRateInv * res)
+                          << "\n  1/dPhaseCAL="
+                          << 1 / (BLOCK_SIZE * srProvider->sampleRateInv * checkV) << std::endl;
                 lastX = x;
             }
+
 #endif
 
             auto dPhase = BLOCK_SIZE * srProvider->sampleRateInv * res;
@@ -182,9 +195,33 @@ struct AHDSRShapedSC : DiscreteStagesEnvelope<BLOCK_SIZE, RangeProvider>
 
         if (!gateActive && stage < base_t::s_release)
         {
-            stage = base_t::s_release;
-            releaseStartValue = this->outputCache[0];
+            if (r == 0)
+            {
+                stage = base_t::s_complete;
+            }
+            else
+            {
+                stage = base_t::s_release;
+                releaseStartValue = this->outputCache[0];
+                phase = 0;
+            }
+        }
+
+        // Accelerate traversal through the state machien for the 0 case
+        if (a == 0.f && stage == base_t::s_attack)
+        {
             phase = 0;
+            stage = base_t::s_hold;
+        }
+        if (h == 0.f && stage == base_t::s_hold)
+        {
+            phase = 0.f;
+            stage = base_t::s_decay;
+        }
+        if (d == 0.f && stage == base_t::s_decay)
+        {
+            phase = 0.f;
+            stage = base_t::s_sustain;
         }
 
         /*