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src/hotspot/cpu/aarch64/vtableStubs_aarch64.cpp

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@@ -45,14 +45,14 @@
 
 #ifndef PRODUCT
 extern "C" void bad_compiled_vtable_index(JavaThread* thread, oop receiver, int index);
 #endif
 
-VtableStub* VtableStubs::create_vtable_stub(int vtable_index) {
+VtableStub* VtableStubs::create_vtable_stub(int vtable_index, bool caller_is_c1) {
   // Read "A word on VtableStub sizing" in share/code/vtableStubs.hpp for details on stub sizing.
   const int stub_code_length = code_size_limit(true);
-  VtableStub* s = new(stub_code_length) VtableStub(true, vtable_index);
+  VtableStub* s = new(stub_code_length) VtableStub(true, vtable_index, caller_is_c1);
   // Can be NULL if there is no free space in the code cache.
   if (s == NULL) {
     return NULL;
   }
 

@@ -61,10 +61,14 @@
   // overflow in subsequently generated stubs.
   address   start_pc;
   int       slop_bytes = 0;
   int       slop_delta = 0;
 
+// No variance was detected in vtable stub sizes. Setting index_dependent_slop == 0 will unveil any deviation from this observation.
+  const int index_dependent_slop     = 0;
+  ByteSize  entry_offset = caller_is_c1 ? Method::from_compiled_value_offset() :  Method::from_compiled_value_ro_offset();
+
   ResourceMark    rm;
   CodeBuffer      cb(s->entry_point(), stub_code_length);
   MacroAssembler* masm = new MacroAssembler(&cb);
 
 #if (!defined(PRODUCT) && defined(COMPILER2))

@@ -114,35 +118,36 @@
 
 #ifndef PRODUCT
   if (DebugVtables) {
     Label L;
     __ cbz(rmethod, L);
-    __ ldr(rscratch1, Address(rmethod, Method::from_compiled_offset()));
+    __ ldr(rscratch1, Address(rmethod, entry_offset));
     __ cbnz(rscratch1, L);
     __ stop("Vtable entry is NULL");
     __ bind(L);
   }
 #endif // PRODUCT
 
   // r0: receiver klass
   // rmethod: Method*
   // r2: receiver
   address ame_addr = __ pc();
-  __ ldr(rscratch1, Address(rmethod, Method::from_compiled_offset()));
+  __ ldr(rscratch1, Address(rmethod, entry_offset));
   __ br(rscratch1);
 
   masm->flush();
-  bookkeeping(masm, tty, s, npe_addr, ame_addr, true, vtable_index, slop_bytes, 0);
+  slop_bytes += index_dependent_slop; // add'l slop for size variance due to large itable offsets
+  bookkeeping(masm, tty, s, npe_addr, ame_addr, true, vtable_index, slop_bytes, index_dependent_slop);
 
   return s;
 }
 
 
-VtableStub* VtableStubs::create_itable_stub(int itable_index) {
+VtableStub* VtableStubs::create_itable_stub(int itable_index, bool caller_is_c1) { 
   // Read "A word on VtableStub sizing" in share/code/vtableStubs.hpp for details on stub sizing.
   const int stub_code_length = code_size_limit(false);
-  VtableStub* s = new(stub_code_length) VtableStub(false, itable_index);
+  VtableStub* s = new(stub_code_length) VtableStub(false, itable_index, caller_is_c1);
   // Can be NULL if there is no free space in the code cache.
   if (s == NULL) {
     return NULL;
   }
   // Count unused bytes in instruction sequences of variable size.

@@ -150,10 +155,14 @@
   // overflow in subsequently generated stubs.
   address   start_pc;
   int       slop_bytes = 0;
   int       slop_delta = 0;
 
+  const int index_dependent_slop = (itable_index == 0) ? 4 :     // code size change with transition from 8-bit to 32-bit constant (@index == 16).
+                                   (itable_index < 16) ? 3 : 0;  // index == 0 generates even shorter code.
+  ByteSize  entry_offset = caller_is_c1 ? Method::from_compiled_value_offset() :  Method::from_compiled_value_ro_offset();
+
   ResourceMark    rm;
   CodeBuffer      cb(s->entry_point(), stub_code_length);
   MacroAssembler* masm = new MacroAssembler(&cb);
 
 #if (!defined(PRODUCT) && defined(COMPILER2))

@@ -219,21 +228,21 @@
 
 #ifdef ASSERT
   if (DebugVtables) {
     Label L2;
     __ cbz(rmethod, L2);
-    __ ldr(rscratch1, Address(rmethod, Method::from_compiled_offset()));
+    __ ldr(rscratch1, Address(rmethod, entry_offset));
     __ cbnz(rscratch1, L2);
     __ stop("compiler entrypoint is null");
     __ bind(L2);
   }
 #endif // ASSERT
 
   // rmethod: Method*
   // j_rarg0: receiver
   address ame_addr = __ pc();
-  __ ldr(rscratch1, Address(rmethod, Method::from_compiled_offset()));
+  __ ldr(rscratch1, Address(rmethod, entry_offset));
   __ br(rscratch1);
 
   __ bind(L_no_such_interface);
   // Handle IncompatibleClassChangeError in itable stubs.
   // More detailed error message.

@@ -242,11 +251,12 @@
   // dirty work.
   assert(SharedRuntime::get_handle_wrong_method_stub() != NULL, "check initialization order");
   __ far_jump(RuntimeAddress(SharedRuntime::get_handle_wrong_method_stub()));
 
   masm->flush();
-  bookkeeping(masm, tty, s, npe_addr, ame_addr, false, itable_index, slop_bytes, 0);
+  slop_bytes += index_dependent_slop; // add'l slop for size variance due to large itable offsets
+  bookkeeping(masm, tty, s, npe_addr, ame_addr, false, itable_index, slop_bytes, index_dependent_slop);
 
   return s;
 }
 
 int VtableStub::pd_code_alignment() {
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