Specialize breakpoint stubs by set of live registers of the stubs they are intercepting.

runtime/vm/stub_code_arm64.cc

Index: runtime/vm/stub_code_arm64.cc
diff --git a/runtime/vm/stub_code_arm64.cc b/runtime/vm/stub_code_arm64.cc
index d6c165ff3de002cfe4784dcf2b369ef414b1b328..a4e43e9e59628c1ff615c12390430b2db5a7e9bc 100644
--- a/runtime/vm/stub_code_arm64.cc
+++ b/runtime/vm/stub_code_arm64.cc
@@ -45,7 +45,6 @@ void StubCode::GenerateCallToRuntimeStub(Assembler* assembler) {
   __ SetPrologueOffset();
   __ Comment("CallToRuntimeStub");
   __ EnterFrame(0);
-  __ SmiUntag(R4);
 
   // Load current Isolate pointer from Context structure into R0.
   __ LoadFieldFromOffset(R0, CTX, Context::isolate_offset(), kNoPP);
@@ -1641,10 +1640,26 @@ void StubCode::GenerateLazyCompileStub(Assembler* assembler) {
 }
 
 
-void StubCode::GenerateBreakpointRuntimeStub(Assembler* assembler) {
+// R5: Contains an ICData.
+void StubCode::GenerateICCallBreakpointStub(Assembler* assembler) {
   __ EnterStubFrame();
-  __ Push(R5);  // Save IC Data.
-  __ Push(R4);  // Save arg. desc.
+  __ Push(R5);
+  __ PushObject(Object::null_object(), PP);  // Space for result.
+  __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
+  __ Pop(R0);
+  __ Pop(R5);
+  __ LeaveStubFrame();
+  __ br(R0);
+}
+
+
+// R5: Contains Smi 0 (need to preserve a GC-safe value for the lazy compile
+// stub).
+// R4: Contains an arguments descriptor.
+void StubCode::GenerateClosureCallBreakpointStub(Assembler* assembler) {
+  __ EnterStubFrame();
+  __ Push(R5);
+  __ Push(R4);
   __ PushObject(Object::null_object(), PP);  // Space for result.
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
   __ Pop(R0);
@@ -1655,6 +1670,15 @@ void StubCode::GenerateBreakpointRuntimeStub(Assembler* assembler) {
 }
 
 
+void StubCode::GenerateRuntimeCallBreakpointStub(Assembler* assembler) {
+  __ EnterStubFrame();
+  __ PushObject(Object::null_object(), PP);  // Space for result.
+  __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
+  __ Pop(R0);
+  __ LeaveStubFrame();
+  __ br(R0);
+}
+
 // Called only from unoptimized code. All relevant registers have been saved.
 void StubCode::GenerateDebugStepCheckStub(
     Assembler* assembler) {