Revert "Revert "[optimizing] Replace FP divide by power of 2""

This reverts commit 067cae2c86627d2edcf01b918ee601774bc76aeb.

Change-Id: Iaaa8772500ea7d3dce6ae0829dc0dc3bbc9c14ca

1 files changed, 12 insertions, 0 deletions

diff --git a/runtime/utils.h b/runtime/utils.h
index 853fa08251..eaafcf0a64 100644
--- a/runtime/utils.h
+++ b/runtime/utils.h
@@ -300,6 +300,18 @@ static inline int WhichPowerOf2(T x) {
   return CTZ(x);
 }
 
+// Return whether x / divisor == x * (1.0f / divisor), for every float x.
+static constexpr bool CanDivideByReciprocalMultiplyFloat(int32_t divisor) {
+  // True, if the most significant bits of divisor are 0.
+  return ((divisor & 0x7fffff) == 0);
+}
+
+// Return whether x / divisor == x * (1.0 / divisor), for every double x.
+static constexpr bool CanDivideByReciprocalMultiplyDouble(int64_t divisor) {
+  // True, if the most significant bits of divisor are 0.
+  return ((divisor & ((UINT64_C(1) << 52) - 1)) == 0);
+}
+
 template<typename T>
 static constexpr int POPCOUNT(T x) {
   return (sizeof(T) == sizeof(uint32_t))