1 files changed, 30 insertions, 5 deletions
diff --git a/lib/Fuzzer/FuzzerTracePC.h b/lib/Fuzzer/FuzzerTracePC.h
index 6523fa06005c4..5ec8c590b4df6 100644
--- a/lib/Fuzzer/FuzzerTracePC.h
+++ b/lib/Fuzzer/FuzzerTracePC.h
@@ -51,7 +51,8 @@ class TracePC {
   // How many bits of PC are used from __sanitizer_cov_trace_pc.
   static const size_t kTracePcBits = 18;
 
-  void HandleInit(uint32_t *start, uint32_t *stop);
+  void HandleInit(uint32_t *Start, uint32_t *Stop);
+  void HandleInline8bitCountersInit(uint8_t *Start, uint8_t *Stop);
   void HandleCallerCallee(uintptr_t Caller, uintptr_t Callee);
   template <class T> void HandleCmp(uintptr_t PC, T Arg1, T Arg2);
   size_t GetTotalPCCoverage();
@@ -104,6 +105,10 @@ private:
   size_t NumModules;  // linker-initialized.
   size_t NumGuards;  // linker-initialized.
 
+  struct { uint8_t *Start, *Stop; } ModuleCounters[4096];
+  size_t NumModulesWithInline8bitCounters;  // linker-initialized.
+  size_t NumInline8bitCounters;
+
   uint8_t *Counters() const;
   uintptr_t *PCs() const;
 
@@ -118,12 +123,24 @@ void ForEachNonZeroByte(const uint8_t *Begin, const uint8_t *End,
                         size_t FirstFeature, Callback Handle8bitCounter) {
   typedef uintptr_t LargeType;
   const size_t Step = sizeof(LargeType) / sizeof(uint8_t);
-  assert(!(reinterpret_cast<uintptr_t>(Begin) % 64));
-  for (auto P = Begin; P < End; P += Step)
+  const size_t StepMask = Step - 1;
+  auto P = Begin;
+  // Iterate by 1 byte until either the alignment boundary or the end.
+  for (; reinterpret_cast<uintptr_t>(P) & StepMask && P < End; P++)
+    if (uint8_t V = *P)
+      Handle8bitCounter(FirstFeature + P - Begin, V);
+
+  // Iterate by Step bytes at a time.
+  for (; P < End; P += Step)
     if (LargeType Bundle = *reinterpret_cast<const LargeType *>(P))
       for (size_t I = 0; I < Step; I++, Bundle >>= 8)
         if (uint8_t V = Bundle & 0xff)
           Handle8bitCounter(FirstFeature + P - Begin + I, V);
+
+  // Iterate by 1 byte until the end.
+  for (; P < End; P++)
+    if (uint8_t V = *P)
+      Handle8bitCounter(FirstFeature + P - Begin, V);
 }
 
 template <class Callback>  // bool Callback(size_t Feature)
@@ -145,8 +162,16 @@ void TracePC::CollectFeatures(Callback HandleFeature) const {
     HandleFeature(Idx * 8 + Bit);
   };
 
-  ForEachNonZeroByte(Counters, Counters + N, 0, Handle8bitCounter);
-  ForEachNonZeroByte(ExtraCountersBegin(), ExtraCountersEnd(), N * 8,
+  size_t FirstFeature = 0;
+  ForEachNonZeroByte(Counters, Counters + N, FirstFeature, Handle8bitCounter);
+  FirstFeature += N * 8;
+  for (size_t i = 0; i < NumModulesWithInline8bitCounters; i++) {
+    ForEachNonZeroByte(ModuleCounters[i].Start, ModuleCounters[i].Stop,
+                       FirstFeature, Handle8bitCounter);
+    FirstFeature += 8 * (ModuleCounters[i].Stop - ModuleCounters[i].Start);
+  }
+
+  ForEachNonZeroByte(ExtraCountersBegin(), ExtraCountersEnd(), FirstFeature,
                      Handle8bitCounter);
 
   if (UseValueProfile)