Generated code for substring slices in x64 and arm.

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index b51d531eb46236b66e76494b13d91a669432420b..c06dc515f3bf1d9dc517d72ce00474998842d8e3 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -3659,6 +3659,42 @@ void MacroAssembler::AllocateAsciiConsString(Register result,
 }
 
 
+void MacroAssembler::AllocateSlicedString(Register result,
+                                          Register scratch1,
+                                          Register scratch2,
+                                          Label* gc_required) {
+  // Allocate heap number in new space.
+  AllocateInNewSpace(SlicedString::kSize,
+                     result,
+                     scratch1,
+                     scratch2,
+                     gc_required,
+                     TAG_OBJECT);
+
+  // Set the map. The other fields are left uninitialized.
+  LoadRoot(kScratchRegister, Heap::kSlicedStringMapRootIndex);
+  movq(FieldOperand(result, HeapObject::kMapOffset), kScratchRegister);
+}
+
+
+void MacroAssembler::AllocateAsciiSlicedString(Register result,
+                                               Register scratch1,
+                                               Register scratch2,
+                                               Label* gc_required) {
+  // Allocate heap number in new space.
+  AllocateInNewSpace(SlicedString::kSize,
+                     result,
+                     scratch1,
+                     scratch2,
+                     gc_required,
+                     TAG_OBJECT);
+
+  // Set the map. The other fields are left uninitialized.
+  LoadRoot(kScratchRegister, Heap::kSlicedAsciiStringMapRootIndex);
+  movq(FieldOperand(result, HeapObject::kMapOffset), kScratchRegister);
+}
+
+
 // Copy memory, byte-by-byte, from source to destination.  Not optimized for
 // long or aligned copies.  The contents of scratch and length are destroyed.
 // Destination is incremented by length, source, length and scratch are