Implement missing features to run Hello world! in checked mode on simulated ARM.

runtime/vm/stub_code_arm.cc

Index: runtime/vm/stub_code_arm.cc
===================================================================
--- runtime/vm/stub_code_arm.cc	(revision 21773)
+++ runtime/vm/stub_code_arm.cc	(working copy)
@@ -1533,8 +1533,89 @@
 }
 
 
+// Implements equality operator when one of the arguments is null
+// (identity check) and updates ICData if necessary.
+// LR: return address.
+// R1: left argument.
+// R0: right argument.
+// R5: ICData.
+// R0: result.
+// TODO(srdjan): Move to VM stubs once Boolean objects become VM objects.
 void StubCode::GenerateEqualityWithNullArgStub(Assembler* assembler) {
-  __ Unimplemented("EqualityWithNullArg Stub");
+  __ EnterStubFrame();
+  static const intptr_t kNumArgsTested = 2;
+#if defined(DEBUG)
+  { Label ok;
+    __ ldr(IP, FieldAddress(R5, ICData::num_args_tested_offset()));
+    __ cmp(IP, ShifterOperand(kNumArgsTested));
+    __ b(&ok, EQ);
+    __ Stop("Incorrect ICData for equality");
+    __ Bind(&ok);
+  }
+#endif  // DEBUG
+  // Check IC data, update if needed.
+  // R5: IC data object (preserved).
+  __ ldr(R6, FieldAddress(R5, ICData::ic_data_offset()));
+  // R6: ic_data_array with check entries: classes and target functions.
+  __ AddImmediate(R6, Array::data_offset() - kHeapObjectTag);
+  // R6: points directly to the first ic data array element.
+
+  Label get_class_id_as_smi, no_match, loop, found;
+  __ Bind(&loop);
+  // Check left.
+  __ mov(R2, ShifterOperand(R1));
+  __ bl(&get_class_id_as_smi);
+  __ ldr(R3, Address(R6, 0 * kWordSize));
+  __ cmp(R2, ShifterOperand(R3));  // Class id match?
+  __ b(&no_match, NE);
+  // Check right.
+  __ mov(R2, ShifterOperand(R0));
+  __ bl(&get_class_id_as_smi);
+  __ ldr(R3, Address(R6, 1 * kWordSize));
+  __ cmp(R2, ShifterOperand(R3));  // Class id match?
+  __ b(&found, EQ);
+  __ Bind(&no_match);
+  // Next check group.
+  __ AddImmediate(R6, kWordSize * ICData::TestEntryLengthFor(kNumArgsTested));
+  __ CompareImmediate(R3, Smi::RawValue(kIllegalCid));  // Done?
+  __ b(&loop, NE);
+  Label update_ic_data;
+  __ b(&update_ic_data);
+
+  __ Bind(&found);
+  const intptr_t count_offset =
+      ICData::CountIndexFor(kNumArgsTested) * kWordSize;
+  __ ldr(IP, Address(R6, count_offset));
+  __ adds(IP, IP, ShifterOperand(Smi::RawValue(1)));
+  __ LoadImmediate(IP, Smi::RawValue(Smi::kMaxValue), VS);  // If overflow.
+  __ str(IP, Address(R6, count_offset));
+
+  Label compute_result;
+  __ Bind(&compute_result);
+  __ cmp(R0, ShifterOperand(R1));
+  __ LoadObject(R0, Bool::False(), NE);
+  __ LoadObject(R0, Bool::True(), EQ);
+  __ LeaveStubFrame();
+  __ Ret();
+
+  __ Bind(&get_class_id_as_smi);
+  // Test if Smi -> load Smi class for comparison.
+  __ tst(R2, ShifterOperand(kSmiTagMask));
+  __ mov(R2, ShifterOperand(Smi::RawValue(kSmiCid)), EQ);
+  __ bx(LR, EQ);
+  __ LoadClassId(R2, R2);
+  __ SmiTag(R2);
+  __ bx(LR);
+
+  __ Bind(&update_ic_data);
+  // R5: ICData
+  __ PushList((1 << R0) | (1 << R1));
+  __ PushObject(Symbols::EqualOperator());  // Target's name.
+  __ Push(R5);  // ICData
+  __ CallRuntime(kUpdateICDataTwoArgsRuntimeEntry);  // Clobbers R4, R5.
+  __ Drop(2);
+  __ PopList((1 << R0) | (1 << R1));
+  __ b(&compute_result);
 }