Make BitField3 a raw uint32 field, and move to the start of the map.

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 475080553ace031321b956c37ebef602a420308e..7bb185076c3214904cb9b98883e9aa577e4fde9f 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -2976,11 +2976,8 @@ void FullCodeGenerator::EmitIsStringWrapperSafeForDefaultValueOf(
   // rbx: descriptor array.
   // rcx: valid entries in the descriptor array.
   // Calculate the end of the descriptor array.
-  __ imulp(rcx, rcx, Immediate(DescriptorArray::kDescriptorSize));
-  SmiIndex index = masm_->SmiToIndex(rdx, rcx, kPointerSizeLog2);
-  __ leap(rcx,
-         Operand(
-             r8, index.reg, index.scale, DescriptorArray::kFirstOffset));
+  __ imull(rcx, rcx, Immediate(DescriptorArray::kDescriptorSize));
+  __ leal(rcx, Operand(r8, rcx, times_4, DescriptorArray::kFirstOffset));
   // Calculate location of the first key name.
   __ addp(r8, Immediate(DescriptorArray::kFirstOffset));
   // Loop through all the keys in the descriptor array. If one of these is the