[libFuzzer] refactor the handling of instrumentation counters so that they are grouped in regions one full page each. Needed for future optimization. NFC

llvm-svn: 352603

1 files changed, 14 insertions, 0 deletions

diff --git a/compiler-rt/lib/fuzzer/FuzzerUtil.h b/compiler-rt/lib/fuzzer/FuzzerUtil.h
index 74fa5bc3107..85c5571d684 100644
--- a/compiler-rt/lib/fuzzer/FuzzerUtil.h
+++ b/compiler-rt/lib/fuzzer/FuzzerUtil.h
@@ -87,6 +87,20 @@ size_t SimpleFastHash(const uint8_t *Data, size_t Size);
 
 inline uint32_t Log(uint32_t X) { return 32 - Clz(X) - 1; }
 
+inline size_t PageSize() { return 4096; }
+inline uint8_t *RoundUpByPage(uint8_t *P) {
+  uintptr_t X = reinterpret_cast<uintptr_t>(P);
+  size_t Mask = PageSize() - 1;
+  X = (X + Mask) & ~Mask;
+  return reinterpret_cast<uint8_t *>(X);
+}
+inline uint8_t *RoundDownByPage(uint8_t *P) {
+  uintptr_t X = reinterpret_cast<uintptr_t>(P);
+  size_t Mask = PageSize() - 1;
+  X = X & ~Mask;
+  return reinterpret_cast<uint8_t *>(X);
+}
+
 }  // namespace fuzzer
 
 #endif  // LLVM_FUZZER_UTIL_H