Revert "Revert "ART: DCHECK zero case for CLZ/CTZ""
This reverts commit 4318d91ea4be673d4deba39d33ac4718d77986a7.
Fix up the lit=-1 case in the arm32 Quick backend; add test case.
Change-Id: I8d0861133db950090ee959f532ede1448683dfa9
diff --git a/runtime/base/bit_utils.h b/runtime/base/bit_utils.h
index 1da6750..1b0d774 100644
--- a/runtime/base/bit_utils.h
+++ b/runtime/base/bit_utils.h
@@ -29,21 +29,28 @@
template<typename T>
static constexpr int CLZ(T x) {
static_assert(std::is_integral<T>::value, "T must be integral");
- // TODO: assert unsigned. There is currently many uses with signed values.
+ static_assert(std::is_unsigned<T>::value, "T must be unsigned");
static_assert(sizeof(T) <= sizeof(long long), // NOLINT [runtime/int] [4]
"T too large, must be smaller than long long");
- return (sizeof(T) == sizeof(uint32_t))
- ? __builtin_clz(x) // TODO: __builtin_clz[ll] has undefined behavior for x=0
- : __builtin_clzll(x);
+ return
+ DCHECK_CONSTEXPR(x != 0, "x must not be zero", T(0))
+ (sizeof(T) == sizeof(uint32_t))
+ ? __builtin_clz(x)
+ : __builtin_clzll(x);
}
template<typename T>
static constexpr int CTZ(T x) {
static_assert(std::is_integral<T>::value, "T must be integral");
- // TODO: assert unsigned. There is currently many uses with signed values.
- return (sizeof(T) == sizeof(uint32_t))
- ? __builtin_ctz(x)
- : __builtin_ctzll(x);
+ // It is not unreasonable to ask for trailing zeros in a negative number. As such, do not check
+ // that T is an unsigned type.
+ 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);
}
template<typename T>