Merge "Revert "ART: DCHECK zero case for CLZ/CTZ""

1 files changed, 8 insertions, 15 deletions

diff --git a/runtime/base/bit_utils.h b/runtime/base/bit_utils.h
index 332012bda9..6f45dc8209 100644
--- a/runtime/base/bit_utils.h
+++ b/runtime/base/bit_utils.h
@@ -29,28 +29,21 @@ namespace art {
 template<typename T>
 static constexpr int CLZ(T x) {
   static_assert(std::is_integral<T>::value, "T must be integral");
-  static_assert(std::is_unsigned<T>::value, "T must be unsigned");
+  // TODO: assert unsigned. There is currently many uses with signed values.
   static_assert(sizeof(T) <= sizeof(long long),  // NOLINT [runtime/int] [4]
                 "T too large, must be smaller than long long");
-  return
-      DCHECK_CONSTEXPR(x != 0, "x must not be zero", T(0))
-      (sizeof(T) == sizeof(uint32_t))
-          ? __builtin_clz(x)
-          : __builtin_clzll(x);
+  return (sizeof(T) == sizeof(uint32_t))
+      ? __builtin_clz(x)  // TODO: __builtin_clz[ll] has undefined behavior for x=0
+      : __builtin_clzll(x);
 }
 
 template<typename T>
 static constexpr int CTZ(T x) {
   static_assert(std::is_integral<T>::value, "T must be integral");
-  // A similar check to the above does not make sense. It isn't as non-intuitive to ask for
-  // trailing zeros in a negative number, and the quick backends do this for immediate encodings.
-  static_assert(sizeof(T) <= sizeof(long long),  // NOLINT [runtime/int] [4]
-                "T too large, must be smaller than long long");
-  return
-      DCHECK_CONSTEXPR(x != 0, "x must not be zero", T(0))
-      (sizeof(T) == sizeof(uint32_t))
-          ? __builtin_ctz(x)
-          : __builtin_ctzll(x);
+  // TODO: assert unsigned. There is currently many uses with signed values.
+  return (sizeof(T) == sizeof(uint32_t))
+      ? __builtin_ctz(x)
+      : __builtin_ctzll(x);
 }
 
 template<typename T>