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src/hotspot/cpu/x86/vtableStubs_x86_32.cpp
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rev 51490 : 8207343: Automate vtable/itable stub size calculation
Reviewed-by: kvn
@@ -1,7 +1,7 @@
/*
- * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
@@ -53,29 +53,38 @@
// rax - inline cache register (is interface for itable stub)
// rbx - method (used when calling out to interpreter)
// Available now, but may become callee-save at some point:
// rsi, rdi
// Note that rax and rdx are also used for return values.
-//
+
VtableStub* VtableStubs::create_vtable_stub(int vtable_index) {
- const int i486_code_length = VtableStub::pd_code_size_limit(true);
- VtableStub* s = new(i486_code_length) VtableStub(true, vtable_index);
+ // 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);
// 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.
+ // We add them to the computed buffer size in order to avoid
+ // 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 slop32 == 0 will unveil any deviation from this observation.
+ const int slop32 = 0;
+
ResourceMark rm;
- CodeBuffer cb(s->entry_point(), i486_code_length);
+ CodeBuffer cb(s->entry_point(), stub_code_length);
MacroAssembler* masm = new MacroAssembler(&cb);
-#ifndef PRODUCT
-
+#if (!defined(PRODUCT) && defined(COMPILER2))
if (CountCompiledCalls) {
__ incrementl(ExternalAddress((address) SharedRuntime::nof_megamorphic_calls_addr()));
}
-#endif /* PRODUCT */
+#endif
// get receiver (need to skip return address on top of stack)
assert(VtableStub::receiver_location() == rcx->as_VMReg(), "receiver expected in rcx");
// get receiver klass
@@ -83,82 +92,95 @@
__ movptr(rax, Address(rcx, oopDesc::klass_offset_in_bytes()));
#ifndef PRODUCT
if (DebugVtables) {
Label L;
+ start_pc = __ pc();
// check offset vs vtable length
__ cmpl(Address(rax, Klass::vtable_length_offset()), vtable_index*vtableEntry::size());
+ slop_delta = 6 - (__ pc() - start_pc); // cmpl varies in length, depending on data
+ slop_bytes += slop_delta;
+ assert(slop_delta >= 0, "negative slop(%d) encountered, adjust code size estimate!", slop_delta);
+
__ jcc(Assembler::greater, L);
__ movl(rbx, vtable_index);
+ // VTABLE TODO: find upper bound for call_VM length.
+ start_pc = __ pc();
__ call_VM(noreg, CAST_FROM_FN_PTR(address, bad_compiled_vtable_index), rcx, rbx);
+ slop_delta = 480 - (__ pc() - start_pc);
+ slop_bytes += slop_delta;
+ assert(slop_delta >= 0, "negative slop(%d) encountered, adjust code size estimate!", slop_delta);
__ bind(L);
}
#endif // PRODUCT
const Register method = rbx;
// load Method* and target address
+ start_pc = __ pc();
__ lookup_virtual_method(rax, vtable_index, method);
+ slop_delta = 6 - (int)(__ pc() - start_pc);
+ slop_bytes += slop_delta;
+ assert(slop_delta >= 0, "negative slop(%d) encountered, adjust code size estimate!", slop_delta);
+#ifndef PRODUCT
if (DebugVtables) {
Label L;
__ cmpptr(method, (int32_t)NULL_WORD);
__ jcc(Assembler::equal, L);
__ cmpptr(Address(method, Method::from_compiled_offset()), (int32_t)NULL_WORD);
__ jcc(Assembler::notZero, L);
__ stop("Vtable entry is NULL");
__ bind(L);
}
+#endif // PRODUCT
- // rax,: receiver klass
+ // rax: receiver klass
// method (rbx): Method*
// rcx: receiver
address ame_addr = __ pc();
__ jmp( Address(method, Method::from_compiled_offset()));
masm->flush();
+ slop_bytes += slop32; // add'l slop for size variance due to large itable offsets
+ bookkeeping(masm, tty, s, npe_addr, ame_addr, true, vtable_index, slop_bytes, slop32);
- if (PrintMiscellaneous && (WizardMode || Verbose)) {
- tty->print_cr("vtable #%d at " PTR_FORMAT "[%d] left over: %d",
- vtable_index, p2i(s->entry_point()),
- (int)(s->code_end() - s->entry_point()),
- (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;
}
VtableStub* VtableStubs::create_itable_stub(int itable_index) {
- // Note well: pd_code_size_limit is the absolute minimum we can get away with. If you
- // add code here, bump the code stub size returned by pd_code_size_limit!
- const int i486_code_length = VtableStub::pd_code_size_limit(false);
- VtableStub* s = new(i486_code_length) VtableStub(false, itable_index);
+ // 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);
// 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.
+ // We add them to the computed buffer size in order to avoid
+ // overflow in subsequently generated stubs.
+ address start_pc;
+ int slop_bytes = 0;
+ int slop_delta = 0;
+ const int slop32 = (itable_index == 0) ? 4 : // code size change with transition from 8-bit to 32-bit constant (@index == 32).
+ (itable_index < 32) ? 3 : 0; // index == 0 generates even shorter code.
ResourceMark rm;
- CodeBuffer cb(s->entry_point(), i486_code_length);
+ CodeBuffer cb(s->entry_point(), stub_code_length);
MacroAssembler* masm = new MacroAssembler(&cb);
- // Entry arguments:
- // rax: CompiledICHolder
- // rcx: Receiver
-
-#ifndef PRODUCT
+#if (!defined(PRODUCT) && defined(COMPILER2))
if (CountCompiledCalls) {
__ incrementl(ExternalAddress((address) SharedRuntime::nof_megamorphic_calls_addr()));
}
#endif /* PRODUCT */
+ // Entry arguments:
+ // rax: CompiledICHolder
+ // rcx: Receiver
+
// Most registers are in use; we'll use rax, rbx, rsi, rdi
// (If we need to make rsi, rdi callee-save, do a push/pop here.)
const Register recv_klass_reg = rsi;
const Register holder_klass_reg = rax; // declaring interface klass (DECC)
const Register resolved_klass_reg = rbx; // resolved interface klass (REFC)
@@ -169,32 +191,48 @@
__ movptr(holder_klass_reg, Address(icholder_reg, CompiledICHolder::holder_metadata_offset()));
Label L_no_such_interface;
// get receiver klass (also an implicit null-check)
- address npe_addr = __ pc();
assert(VtableStub::receiver_location() == rcx->as_VMReg(), "receiver expected in rcx");
+ address npe_addr = __ pc();
__ load_klass(recv_klass_reg, rcx);
+ start_pc = __ pc();
+
// Receiver subtype check against REFC.
// Destroys recv_klass_reg value.
__ lookup_interface_method(// inputs: rec. class, interface
recv_klass_reg, resolved_klass_reg, noreg,
// outputs: scan temp. reg1, scan temp. reg2
recv_klass_reg, temp_reg,
L_no_such_interface,
/*return_method=*/false);
+ const ptrdiff_t typecheckSize = __ pc() - start_pc;
+ start_pc = __ pc();
+
// Get selected method from declaring class and itable index
const Register method = rbx;
__ load_klass(recv_klass_reg, rcx); // restore recv_klass_reg
__ lookup_interface_method(// inputs: rec. class, interface, itable index
recv_klass_reg, holder_klass_reg, itable_index,
// outputs: method, scan temp. reg
method, temp_reg,
L_no_such_interface);
+ const ptrdiff_t lookupSize = __ pc() - start_pc;
+
+ // We expect we need slop32 extra bytes. Reason:
+ // The emitted code in lookup_interface_method changes when itable_index exceeds 31.
+ // For windows, a narrow estimate was found to be 104. Other OSes not tested.
+ const ptrdiff_t estimate = 104;
+ const ptrdiff_t codesize = typecheckSize + lookupSize + slop32;
+ slop_delta = (int)(estimate - codesize);
+ slop_bytes += slop_delta;
+ assert(slop_delta >= 0, "itable #%d: Code size estimate (%d) for lookup_interface_method too small, required: %d", itable_index, (int)estimate, (int)codesize);
+
// method (rbx): Method*
// rcx: receiver
#ifdef ASSERT
if (DebugVtables) {
@@ -217,72 +255,17 @@
// We force resolving of the call site by jumping to the "handle
// wrong method" stub, and so let the interpreter runtime do all the
// dirty work.
__ jump(RuntimeAddress(SharedRuntime::get_handle_wrong_method_stub()));
- __ flush();
-
- if (PrintMiscellaneous && (WizardMode || Verbose)) {
- tty->print_cr("itable #%d at " PTR_FORMAT "[%d] left over: %d",
- itable_index, p2i(s->entry_point()),
- (int)(s->code_end() - s->entry_point()),
- (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");
+ masm->flush();
+ slop_bytes += slop32; // add'l slop for size variance due to large itable offsets
+ bookkeeping(masm, tty, s, npe_addr, ame_addr, false, itable_index, slop_bytes, slop32);
- s->set_exception_points(npe_addr, ame_addr);
return s;
}
-
-
-int VtableStub::pd_code_size_limit(bool is_vtable_stub) {
- if (is_vtable_stub) {
- // Vtable stub size
- return (DebugVtables ? 210 : 16) + (CountCompiledCalls ? 6 : 0);
- } else {
- // Itable stub size
- return (DebugVtables ? 256 : 110) + (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() {
- return wordSize;
+ // x86 cache line size is 64 bytes, but we want to limit alignment loss.
+ const unsigned int icache_line_size = wordSize;
+ return icache_line_size;
}
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