Esoteric bit operations.

runtime/lib/integers.cc

Index: runtime/lib/integers.cc
diff --git a/runtime/lib/integers.cc b/runtime/lib/integers.cc
index 5be23af2fea9dbcd0f8a48ea9d524ea1cfc778ac..84dc9d6205fa1c82c40e82ebc78b3aff4ceb2af8 100644
--- a/runtime/lib/integers.cc
+++ b/runtime/lib/integers.cc
@@ -35,6 +35,12 @@ static bool CheckInteger(const Integer& i) {
 }
 
 
+static int BitLengthInt64(int64_t value) {
+  value ^= value >> (8 * sizeof(value) - 1);  // flip bits if negative.
+  return value == 0 ? 0 : Utils::HighestBit(value) + 1;
+}
+
+
 DEFINE_NATIVE_ENTRY(Integer_bitAndFromInteger, 2) {
   const Integer& right = Integer::CheckedHandle(arguments->NativeArgAt(0));
   GET_NON_NULL_NATIVE_ARGUMENT(Integer, left, arguments->NativeArgAt(1));
@@ -327,6 +333,18 @@ DEFINE_NATIVE_ENTRY(Smi_bitNegate, 1) {
 }
 
 
+DEFINE_NATIVE_ENTRY(Smi_bitLength, 1) {
+  const Smi& operand = Smi::CheckedHandle(arguments->NativeArgAt(0));
+  if (FLAG_trace_intrinsified_natives) {
+    OS::Print("Smi_bitLength: %s\n", operand.ToCString());
+  }
+  int64_t value = operand.AsInt64Value();
+  intptr_t result = BitLengthInt64(value);
+  ASSERT(Smi::IsValid(result));
+  return Smi::New(result);
+}
+
+
 // Mint natives.
 
 DEFINE_NATIVE_ENTRY(Mint_bitNegate, 1) {
@@ -340,6 +358,19 @@ DEFINE_NATIVE_ENTRY(Mint_bitNegate, 1) {
 }
 
 
+DEFINE_NATIVE_ENTRY(Mint_bitLength, 1) {
+  const Mint& operand = Mint::CheckedHandle(arguments->NativeArgAt(0));
+  ASSERT(CheckInteger(operand));
+  if (FLAG_trace_intrinsified_natives) {
+    OS::Print("Mint_bitLength: %s\n", operand.ToCString());
+  }
+  int64_t value = operand.AsInt64Value();
+  intptr_t result = BitLengthInt64(value);
+  ASSERT(Smi::IsValid(result));
+  return Smi::New(result);
+}
+
+
 DEFINE_NATIVE_ENTRY(Mint_shlFromInt, 2) {
   // Use the preallocated out of memory exception to avoid calling
   // into dart code or allocating any code.
@@ -362,6 +393,12 @@ DEFINE_NATIVE_ENTRY(Bigint_bitNegate, 1) {
 }
 
 
+DEFINE_NATIVE_ENTRY(Bigint_bitLength, 1) {
+  const Bigint& value = Bigint::CheckedHandle(arguments->NativeArgAt(0));
+  return Integer::New(BigintOperations::BitLength(value));
+}
+
+
 DEFINE_NATIVE_ENTRY(Bigint_shlFromInt, 2) {
   // Use the preallocated out of memory exception to avoid calling
   // into dart code or allocating any code.