Intrinsify OnebyteString's hashcode. Next step is to inline it.

runtime/vm/intrinsifier_x64.cc

Index: runtime/vm/intrinsifier_x64.cc
===================================================================
--- runtime/vm/intrinsifier_x64.cc	(revision 19153)
+++ runtime/vm/intrinsifier_x64.cc	(working copy)
@@ -1394,6 +1394,77 @@
   return true;
 }
 
+
+bool Intrinsifier::OneByteString_getHashCode(Assembler* assembler) {
+  Label compute_hash;
+  __ movq(RBX, Address(RSP, + 1 * kWordSize));  // OneByteString object.
+  __ movq(RAX, FieldAddress(RBX, String::hash_offset()));
+  __ cmpq(RAX, Immediate(0));
+  __ j(EQUAL, &compute_hash, Assembler::kNearJump);
+  __ ret();
+
+  __ Bind(&compute_hash);
+  // Hash not yet computed, use algorithm of class StringHasher.
+  __ movq(RCX, FieldAddress(RBX, String::length_offset()));
+  __ SmiUntag(RCX);
+  __ xorq(RAX, RAX);
+  __ xorq(RDI, RDI);
+  // RBX: Instance of OneByteString.
+  // RCX: String length, untagged integer.
+  // RDI: Loop counter, untagged integer.
+  // RAX: Hash code, untagged integer.
+  Label loop, done, set_hash_code;
+  __ Bind(&loop);
+  __ cmpq(RDI, RCX);
+  __ j(EQUAL, &done, Assembler::kNearJump);
+  // Add to hash code: (hash_ is uint32)
+  // hash_ += ch;
+  // hash_ += hash_ << 10;
+  // hash_ ^= hash_ >> 6;
+  // Get one characters (ch).
+  __ movzxb(RDX, FieldAddress(RBX, RDI, TIMES_1, OneByteString::data_offset()));
+  // RDX: ch and temporary.
+  __ addl(RAX, RDX);
+  __ movq(RDX, RAX);
+  __ shll(RDX, Immediate(10));
+  __ addl(RAX, RDX);
+  __ movq(RDX, RAX);
+  __ shrl(RDX, Immediate(6));
+  __ xorl(RAX, RDX);
+
+  __ incq(RDI);
+  __ jmp(&loop, Assembler::kNearJump);
+
+  __ Bind(&done);
+  // Finalize:
+  // hash_ += hash_ << 3;
+  // hash_ ^= hash_ >> 11;
+  // hash_ += hash_ << 15;
+  __ movq(RDX, RAX);
+  __ shll(RDX, Immediate(3));
+  __ addl(RAX, RDX);
+  __ movq(RDX, RAX);
+  __ shrl(RDX, Immediate(11));
+  __ xorl(RAX, RDX);
+  __ movq(RDX, RAX);
+  __ shll(RDX, Immediate(15));
+  __ addl(RAX, RDX);
+  // hash_ = hash_ & ((static_cast<intptr_t>(1) << bits) - 1);
+  __ andl(RAX,
+      Immediate(((static_cast<intptr_t>(1) << String::kHashBits) - 1)));
+
+  // return hash_ == 0 ? 1 : hash_;
+  __ cmpq(RAX, Immediate(0));
+  __ j(NOT_EQUAL, &set_hash_code, Assembler::kNearJump);
+  __ incq(RAX);
+  __ Bind(&set_hash_code);
+  __ SmiTag(RAX);
+  __ movq(FieldAddress(RBX, String::hash_offset()), RAX);
+  __ ret();
+  return true;
+}
+
+
 #undef __
 
 }  // namespace dart