1.1 --- a/src/cpu/x86/vm/vtableStubs_x86_64.cpp Tue Apr 07 19:04:24 2009 -0700
1.2 +++ b/src/cpu/x86/vm/vtableStubs_x86_64.cpp Wed Apr 08 00:12:59 2009 -0700
1.3 @@ -106,6 +106,9 @@
1.4 (int)(s->code_end() - __ pc()));
1.5 }
1.6 guarantee(__ pc() <= s->code_end(), "overflowed buffer");
1.7 + // shut the door on sizing bugs
1.8 + int slop = 3; // 32-bit offset is this much larger than an 8-bit one
1.9 + assert(vtable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
1.10
1.11 s->set_exception_points(npe_addr, ame_addr);
1.12 return s;
1.13 @@ -191,6 +194,9 @@
1.14 (int)(s->code_end() - __ pc()));
1.15 }
1.16 guarantee(__ pc() <= s->code_end(), "overflowed buffer");
1.17 + // shut the door on sizing bugs
1.18 + int slop = 3; // 32-bit offset is this much larger than an 8-bit one
1.19 + assert(itable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
1.20
1.21 s->set_exception_points(npe_addr, ame_addr);
1.22 return s;
1.23 @@ -206,6 +212,39 @@
1.24 return (DebugVtables ? 512 : 72) + (CountCompiledCalls ? 13 : 0) +
1.25 (UseCompressedOops ? 32 : 0); // 2 leaqs
1.26 }
1.27 + // In order to tune these parameters, run the JVM with VM options
1.28 + // +PrintMiscellaneous and +WizardMode to see information about
1.29 + // actual itable stubs. Look for lines like this:
1.30 + // itable #1 at 0x5551212[71] left over: 3
1.31 + // Reduce the constants so that the "left over" number is >=3
1.32 + // for the common cases.
1.33 + // Do not aim at a left-over number of zero, because a
1.34 + // large vtable or itable index (>= 32) will require a 32-bit
1.35 + // immediate displacement instead of an 8-bit one.
1.36 + //
1.37 + // The JVM98 app. _202_jess has a megamorphic interface call.
1.38 + // The itable code looks like this:
1.39 + // Decoding VtableStub itbl[1]@12
1.40 + // mov 0x8(%rsi),%r10
1.41 + // mov 0x198(%r10),%r11d
1.42 + // lea 0x218(%r10,%r11,8),%r11
1.43 + // lea 0x8(%r10),%r10
1.44 + // mov (%r11),%rbx
1.45 + // cmp %rbx,%rax
1.46 + // je success
1.47 + // loop:
1.48 + // test %rbx,%rbx
1.49 + // je throw_icce
1.50 + // add $0x10,%r11
1.51 + // mov (%r11),%rbx
1.52 + // cmp %rbx,%rax
1.53 + // jne loop
1.54 + // success:
1.55 + // mov 0x8(%r11),%r11d
1.56 + // mov (%r10,%r11,1),%rbx
1.57 + // jmpq *0x60(%rbx)
1.58 + // throw_icce:
1.59 + // jmpq throw_ICCE_entry
1.60 }
1.61
1.62 int VtableStub::pd_code_alignment() {
