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6827505: sizing logic for vtable and itable stubs needs self-check

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Asserts and comments to help maintain the correct sizing of certain stubs

Reviewed-by: kvn
This commit is contained in:
John R Rose 2009-04-08 00:12:59 -07:00
parent ca3a3504be
commit 318da3f68c
4 changed files with 130 additions and 2 deletions
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50
hotspot/src/cpu/sparc/vm/vtableStubs_sparc.cpp
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@ -114,6 +114,9 @@ VtableStub* VtableStubs::create_vtable_stub(int vtable_index) {
(int)(s->code_end() - __ pc()));
}
guarantee(__ pc() <= s->code_end(), "overflowed buffer");
// shut the door on sizing bugs
int slop = 2*BytesPerInstWord; // 32-bit offset is this much larger than a 13-bit one
assert(vtable_index > 10 || __ pc() + slop <= s->code_end(), "room for sethi;add");
s->set_exception_points(npe_addr, ame_addr);
return s;
@ -208,6 +211,9 @@ VtableStub* VtableStubs::create_itable_stub(int itable_index) {
(int)(s->code_end() - __ pc()));
}
guarantee(__ pc() <= s->code_end(), "overflowed buffer");
// shut the door on sizing bugs
int slop = 2*BytesPerInstWord; // 32-bit offset is this much larger than a 13-bit one
assert(itable_index > 10 || __ pc() + slop <= s->code_end(), "room for sethi;add");
s->set_exception_points(npe_addr, ame_addr);
return s;
@ -233,6 +239,50 @@ int VtableStub::pd_code_size_limit(bool is_vtable_stub) {
return (basic + slop);
}
}
// In order to tune these parameters, run the JVM with VM options
// +PrintMiscellaneous and +WizardMode to see information about
// actual itable stubs. Look for lines like this:
// itable #1 at 0x5551212[116] left over: 8
// Reduce the constants so that the "left over" number is 8
// Do not aim at a left-over number of zero, because a very
// large vtable or itable offset (> 4K) will require an extra
// sethi/or pair of instructions.
//
// The JVM98 app. _202_jess has a megamorphic interface call.
// The itable code looks like this:
// Decoding VtableStub itbl[1]@16
// ld [ %o0 + 4 ], %g3
// save %sp, -64, %sp
// ld [ %g3 + 0xe8 ], %l2
// sll %l2, 2, %l2
// add %l2, 0x134, %l2
// and %l2, -8, %l2 ! NOT_LP64 only
// add %g3, %l2, %l2
// add %g3, 4, %g3
// ld [ %l2 ], %l5
// brz,pn %l5, throw_icce
// cmp %l5, %g5
// be %icc, success
// add %l2, 8, %l2
// loop:
// ld [ %l2 ], %l5
// brz,pn %l5, throw_icce
// cmp %l5, %g5
// bne,pn %icc, loop
// add %l2, 8, %l2
// success:
// ld [ %l2 + -4 ], %l2
// ld [ %g3 + %l2 ], %l5
// restore %l5, 0, %g5
// ld [ %g5 + 0x44 ], %g3
// jmp %g3
// nop
// throw_icce:
// sethi %hi(throw_ICCE_entry), %g3
// ! 5 more instructions here, LP64_ONLY
// jmp %g3 + %lo(throw_ICCE_entry)
// restore
}

41
hotspot/src/cpu/x86/vm/vtableStubs_x86_32.cpp
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@ -108,6 +108,9 @@ VtableStub* VtableStubs::create_vtable_stub(int vtable_index) {
(int)(s->code_end() - __ pc()));
}
guarantee(__ pc() <= s->code_end(), "overflowed buffer");
// shut the door on sizing bugs
int slop = 3; // 32-bit offset is this much larger than an 8-bit one
assert(vtable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
s->set_exception_points(npe_addr, ame_addr);
return s;
@ -181,6 +184,9 @@ VtableStub* VtableStubs::create_itable_stub(int itable_index) {
(int)(s->code_end() - __ pc()));
}
guarantee(__ pc() <= s->code_end(), "overflowed buffer");
// shut the door on sizing bugs
int slop = 3; // 32-bit offset is this much larger than an 8-bit one
assert(itable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
s->set_exception_points(npe_addr, ame_addr);
return s;
@ -196,6 +202,41 @@ int VtableStub::pd_code_size_limit(bool is_vtable_stub) {
// Itable stub size
return (DebugVtables ? 256 : 66) + (CountCompiledCalls ? 6 : 0);
}
// In order to tune these parameters, run the JVM with VM options
// +PrintMiscellaneous and +WizardMode to see information about
// actual itable stubs. Look for lines like this:
// itable #1 at 0x5551212[65] left over: 3
// Reduce the constants so that the "left over" number is >=3
// for the common cases.
// Do not aim at a left-over number of zero, because a
// large vtable or itable index (> 16) will require a 32-bit
// immediate displacement instead of an 8-bit one.
//
// The JVM98 app. _202_jess has a megamorphic interface call.
// The itable code looks like this:
// Decoding VtableStub itbl[1]@1
// mov 0x4(%ecx),%esi
// mov 0xe8(%esi),%edi
// lea 0x130(%esi,%edi,4),%edi
// add $0x7,%edi
// and $0xfffffff8,%edi
// lea 0x4(%esi),%esi
// mov (%edi),%ebx
// cmp %ebx,%eax
// je success
// loop:
// test %ebx,%ebx
// je throw_icce
// add $0x8,%edi
// mov (%edi),%ebx
// cmp %ebx,%eax
// jne loop
// success:
// mov 0x4(%edi),%edi
// mov (%esi,%edi,1),%ebx
// jmp *0x44(%ebx)
// throw_icce:
// jmp throw_ICCE_entry
}
int VtableStub::pd_code_alignment() {

39
hotspot/src/cpu/x86/vm/vtableStubs_x86_64.cpp
View File

@ -106,6 +106,9 @@ VtableStub* VtableStubs::create_vtable_stub(int vtable_index) {
(int)(s->code_end() - __ pc()));
}
guarantee(__ pc() <= s->code_end(), "overflowed buffer");
// shut the door on sizing bugs
int slop = 3; // 32-bit offset is this much larger than an 8-bit one
assert(vtable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
s->set_exception_points(npe_addr, ame_addr);
return s;
@ -191,6 +194,9 @@ VtableStub* VtableStubs::create_itable_stub(int itable_index) {
(int)(s->code_end() - __ pc()));
}
guarantee(__ pc() <= s->code_end(), "overflowed buffer");
// shut the door on sizing bugs
int slop = 3; // 32-bit offset is this much larger than an 8-bit one
assert(itable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
s->set_exception_points(npe_addr, ame_addr);
return s;
@ -206,6 +212,39 @@ int VtableStub::pd_code_size_limit(bool is_vtable_stub) {
return (DebugVtables ? 512 : 72) + (CountCompiledCalls ? 13 : 0) +
(UseCompressedOops ? 32 : 0); // 2 leaqs
}
// In order to tune these parameters, run the JVM with VM options
// +PrintMiscellaneous and +WizardMode to see information about
// actual itable stubs. Look for lines like this:
// itable #1 at 0x5551212[71] left over: 3
// Reduce the constants so that the "left over" number is >=3
// for the common cases.
// Do not aim at a left-over number of zero, because a
// large vtable or itable index (>= 32) will require a 32-bit
// immediate displacement instead of an 8-bit one.
//
// The JVM98 app. _202_jess has a megamorphic interface call.
// The itable code looks like this:
// Decoding VtableStub itbl[1]@12
// mov 0x8(%rsi),%r10
// mov 0x198(%r10),%r11d
// lea 0x218(%r10,%r11,8),%r11
// lea 0x8(%r10),%r10
// mov (%r11),%rbx
// cmp %rbx,%rax
// je success
// loop:
// test %rbx,%rbx
// je throw_icce
// add $0x10,%r11
// mov (%r11),%rbx
// cmp %rbx,%rax
// jne loop
// success:
// mov 0x8(%r11),%r11d
// mov (%r10,%r11,1),%rbx
// jmpq *0x60(%rbx)
// throw_icce:
// jmpq throw_ICCE_entry
}
int VtableStub::pd_code_alignment() {

2
hotspot/src/share/vm/code/vtableStubs.cpp
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@ -107,13 +107,11 @@ address VtableStubs::create_stub(bool is_vtable_stub, int vtable_index, methodOo
s = create_itable_stub(vtable_index);
}
enter(is_vtable_stub, vtable_index, s);
#ifndef PRODUCT
if (PrintAdapterHandlers) {
tty->print_cr("Decoding VtableStub %s[%d]@%d",
is_vtable_stub? "vtbl": "itbl", vtable_index, VtableStub::receiver_location());
Disassembler::decode(s->code_begin(), s->code_end());
}
#endif
}
return s->entry_point();
}