Track JS allocations as they arrive with no affection on performance when tracking is switched off

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 171112fa7d37a37d01a2a22aa2e41ac1322985d1..8c69f8299f2c9007807c1c11739c289dff8689ec 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -4940,9 +4940,19 @@ void SubStringStub::Generate(MacroAssembler* masm) {
     STATIC_ASSERT((kStringEncodingMask & kOneByteStringTag) != 0);
     STATIC_ASSERT((kStringEncodingMask & kTwoByteStringTag) == 0);
     __ testb(rbx, Immediate(kStringEncodingMask));
-    __ j(zero, &two_byte_slice, Label::kNear);
+    if (masm->emit_allocations_tracking_code()) {
+      // Make a long jump due to RecordObjectAllocation inside
+      // MacroAssembler::Allocate
+      __ j(zero, &two_byte_slice);
+    } else {
+      __ j(zero, &two_byte_slice, Label::kNear);
+    }
     __ AllocateAsciiSlicedString(rax, rbx, r14, &runtime);
-    __ jmp(&set_slice_header, Label::kNear);
+    if (masm->emit_allocations_tracking_code()) {
+      __ jmp(&set_slice_header);
+    } else {
+      __ jmp(&set_slice_header, Label::kNear);
+    }
     __ bind(&two_byte_slice);
     __ AllocateTwoByteSlicedString(rax, rbx, r14, &runtime);
     __ bind(&set_slice_header);