Thu, 06 Mar 2014 10:55:28 -0800
8035647: PPC64: Support for elf v2 abi.
Summary: ELFv2 ABI used by the little endian PowerPC64 on Linux.
Reviewed-by: kvn
Contributed-by: asmundak@google.com
1 /*
2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
3 * Copyright 2012, 2013 SAP AG. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
26 #include "precompiled.hpp"
27 #include "asm/macroAssembler.inline.hpp"
28 #include "interpreter/interpreter.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "prims/methodHandles.hpp"
32 #define __ _masm->
34 #ifdef CC_INTERP
35 #define EXCEPTION_ENTRY StubRoutines::throw_NullPointerException_at_call_entry()
36 #else
37 #define EXCEPTION_ENTRY Interpreter::throw_NullPointerException_entry()
38 #endif
40 #ifdef PRODUCT
41 #define BLOCK_COMMENT(str) // nothing
42 #else
43 #define BLOCK_COMMENT(str) __ block_comment(str)
44 #endif
46 #define BIND(label) bind(label); BLOCK_COMMENT(#label ":")
48 // Workaround for C++ overloading nastiness on '0' for RegisterOrConstant.
49 inline static RegisterOrConstant constant(int value) {
50 return RegisterOrConstant(value);
51 }
53 void MethodHandles::load_klass_from_Class(MacroAssembler* _masm, Register klass_reg, Register temp_reg, Register temp2_reg) {
54 if (VerifyMethodHandles)
55 verify_klass(_masm, klass_reg, SystemDictionary::WK_KLASS_ENUM_NAME(java_lang_Class), temp_reg, temp2_reg,
56 "MH argument is a Class");
57 __ ld(klass_reg, java_lang_Class::klass_offset_in_bytes(), klass_reg);
58 }
60 #ifdef ASSERT
61 static int check_nonzero(const char* xname, int x) {
62 assert(x != 0, err_msg("%s should be nonzero", xname));
63 return x;
64 }
65 #define NONZERO(x) check_nonzero(#x, x)
66 #else //ASSERT
67 #define NONZERO(x) (x)
68 #endif //ASSERT
70 #ifdef ASSERT
71 void MethodHandles::verify_klass(MacroAssembler* _masm,
72 Register obj_reg, SystemDictionary::WKID klass_id,
73 Register temp_reg, Register temp2_reg,
74 const char* error_message) {
75 Klass** klass_addr = SystemDictionary::well_known_klass_addr(klass_id);
76 KlassHandle klass = SystemDictionary::well_known_klass(klass_id);
77 Label L_ok, L_bad;
78 BLOCK_COMMENT("verify_klass {");
79 __ verify_oop(obj_reg);
80 __ cmpdi(CCR0, obj_reg, 0);
81 __ beq(CCR0, L_bad);
82 __ load_klass(temp_reg, obj_reg);
83 __ load_const_optimized(temp2_reg, (address) klass_addr);
84 __ ld(temp2_reg, 0, temp2_reg);
85 __ cmpd(CCR0, temp_reg, temp2_reg);
86 __ beq(CCR0, L_ok);
87 __ ld(temp_reg, klass->super_check_offset(), temp_reg);
88 __ cmpd(CCR0, temp_reg, temp2_reg);
89 __ beq(CCR0, L_ok);
90 __ BIND(L_bad);
91 __ stop(error_message);
92 __ BIND(L_ok);
93 BLOCK_COMMENT("} verify_klass");
94 }
96 void MethodHandles::verify_ref_kind(MacroAssembler* _masm, int ref_kind, Register member_reg, Register temp) {
97 Label L;
98 BLOCK_COMMENT("verify_ref_kind {");
99 __ load_sized_value(temp, NONZERO(java_lang_invoke_MemberName::flags_offset_in_bytes()), member_reg,
100 sizeof(u4), /*is_signed*/ false);
101 // assert(sizeof(u4) == sizeof(java.lang.invoke.MemberName.flags), "");
102 __ srwi( temp, temp, java_lang_invoke_MemberName::MN_REFERENCE_KIND_SHIFT);
103 __ andi(temp, temp, java_lang_invoke_MemberName::MN_REFERENCE_KIND_MASK);
104 __ cmpwi(CCR1, temp, ref_kind);
105 __ beq(CCR1, L);
106 { char* buf = NEW_C_HEAP_ARRAY(char, 100, mtInternal);
107 jio_snprintf(buf, 100, "verify_ref_kind expected %x", ref_kind);
108 if (ref_kind == JVM_REF_invokeVirtual ||
109 ref_kind == JVM_REF_invokeSpecial)
110 // could do this for all ref_kinds, but would explode assembly code size
111 trace_method_handle(_masm, buf);
112 __ stop(buf);
113 }
114 BLOCK_COMMENT("} verify_ref_kind");
115 __ BIND(L);
116 }
118 #endif // ASSERT
120 void MethodHandles::jump_from_method_handle(MacroAssembler* _masm, Register method, Register target, Register temp,
121 bool for_compiler_entry) {
122 assert(method == R19_method, "interpreter calling convention");
123 assert_different_registers(method, target, temp);
125 if (!for_compiler_entry && JvmtiExport::can_post_interpreter_events()) {
126 Label run_compiled_code;
127 // JVMTI events, such as single-stepping, are implemented partly by avoiding running
128 // compiled code in threads for which the event is enabled. Check here for
129 // interp_only_mode if these events CAN be enabled.
130 __ verify_thread();
131 __ lwz(temp, in_bytes(JavaThread::interp_only_mode_offset()), R16_thread);
132 __ cmplwi(CCR0, temp, 0);
133 __ beq(CCR0, run_compiled_code);
134 __ ld(target, in_bytes(Method::interpreter_entry_offset()), R19_method);
135 __ mtctr(target);
136 __ bctr();
137 __ BIND(run_compiled_code);
138 }
140 const ByteSize entry_offset = for_compiler_entry ? Method::from_compiled_offset() :
141 Method::from_interpreted_offset();
142 __ ld(target, in_bytes(entry_offset), R19_method);
143 __ mtctr(target);
144 __ bctr();
145 }
148 void MethodHandles::jump_to_lambda_form(MacroAssembler* _masm,
149 Register recv, Register method_temp,
150 Register temp2, Register temp3,
151 bool for_compiler_entry) {
152 BLOCK_COMMENT("jump_to_lambda_form {");
153 // This is the initial entry point of a lazy method handle.
154 // After type checking, it picks up the invoker from the LambdaForm.
155 assert_different_registers(recv, method_temp, temp2); // temp3 is only passed on
156 assert(method_temp == R19_method, "required register for loading method");
158 // Load the invoker, as MH -> MH.form -> LF.vmentry
159 __ verify_oop(recv);
160 __ load_heap_oop_not_null(method_temp, NONZERO(java_lang_invoke_MethodHandle::form_offset_in_bytes()), recv);
161 __ verify_oop(method_temp);
162 __ load_heap_oop_not_null(method_temp, NONZERO(java_lang_invoke_LambdaForm::vmentry_offset_in_bytes()), method_temp);
163 __ verify_oop(method_temp);
164 // the following assumes that a Method* is normally compressed in the vmtarget field:
165 __ ld(method_temp, NONZERO(java_lang_invoke_MemberName::vmtarget_offset_in_bytes()), method_temp);
167 if (VerifyMethodHandles && !for_compiler_entry) {
168 // make sure recv is already on stack
169 __ ld(temp2, in_bytes(Method::const_offset()), method_temp);
170 __ load_sized_value(temp2, in_bytes(ConstMethod::size_of_parameters_offset()), temp2,
171 sizeof(u2), /*is_signed*/ false);
172 // assert(sizeof(u2) == sizeof(ConstMethod::_size_of_parameters), "");
173 Label L;
174 __ ld(temp2, __ argument_offset(temp2, temp2, 0), CC_INTERP_ONLY(R17_tos) NOT_CC_INTERP(R15_esp));
175 __ cmpd(CCR1, temp2, recv);
176 __ beq(CCR1, L);
177 __ stop("receiver not on stack");
178 __ BIND(L);
179 }
181 jump_from_method_handle(_masm, method_temp, temp2, temp3, for_compiler_entry);
182 BLOCK_COMMENT("} jump_to_lambda_form");
183 }
187 // Code generation
188 address MethodHandles::generate_method_handle_interpreter_entry(MacroAssembler* _masm,
189 vmIntrinsics::ID iid) {
190 const bool not_for_compiler_entry = false; // this is the interpreter entry
191 assert(is_signature_polymorphic(iid), "expected invoke iid");
192 if (iid == vmIntrinsics::_invokeGeneric ||
193 iid == vmIntrinsics::_compiledLambdaForm) {
194 // Perhaps surprisingly, the symbolic references visible to Java are not directly used.
195 // They are linked to Java-generated adapters via MethodHandleNatives.linkMethod.
196 // They all allow an appendix argument.
197 __ stop("Should not reach here"); // empty stubs make SG sick
198 return NULL;
199 }
201 Register argbase = CC_INTERP_ONLY(R17_tos) NOT_CC_INTERP(R15_esp); // parameter (preserved)
202 Register argslot = R3;
203 Register temp1 = R6;
204 Register param_size = R7;
206 // here's where control starts out:
207 __ align(CodeEntryAlignment);
208 address entry_point = __ pc();
210 if (VerifyMethodHandles) {
211 Label L;
212 BLOCK_COMMENT("verify_intrinsic_id {");
213 __ load_sized_value(temp1, Method::intrinsic_id_offset_in_bytes(), R19_method,
214 sizeof(u1), /*is_signed*/ false);
215 // assert(sizeof(u1) == sizeof(Method::_intrinsic_id), "");
216 __ cmpwi(CCR1, temp1, (int) iid);
217 __ beq(CCR1, L);
218 if (iid == vmIntrinsics::_linkToVirtual ||
219 iid == vmIntrinsics::_linkToSpecial) {
220 // could do this for all kinds, but would explode assembly code size
221 trace_method_handle(_masm, "bad Method*:intrinsic_id");
222 }
223 __ stop("bad Method*::intrinsic_id");
224 __ BIND(L);
225 BLOCK_COMMENT("} verify_intrinsic_id");
226 }
228 // First task: Find out how big the argument list is.
229 int ref_kind = signature_polymorphic_intrinsic_ref_kind(iid);
230 assert(ref_kind != 0 || iid == vmIntrinsics::_invokeBasic, "must be _invokeBasic or a linkTo intrinsic");
231 if (ref_kind == 0 || MethodHandles::ref_kind_has_receiver(ref_kind)) {
232 __ ld(param_size, in_bytes(Method::const_offset()), R19_method);
233 __ load_sized_value(param_size, in_bytes(ConstMethod::size_of_parameters_offset()), param_size,
234 sizeof(u2), /*is_signed*/ false);
235 // assert(sizeof(u2) == sizeof(ConstMethod::_size_of_parameters), "");
236 } else {
237 DEBUG_ONLY(param_size = noreg);
238 }
240 Register tmp_mh = noreg;
241 if (!is_signature_polymorphic_static(iid)) {
242 __ ld(tmp_mh = temp1, __ argument_offset(param_size, param_size, 0), argbase);
243 DEBUG_ONLY(param_size = noreg);
244 }
246 if (TraceMethodHandles) {
247 if (tmp_mh != noreg)
248 __ mr(R23_method_handle, tmp_mh); // make stub happy
249 trace_method_handle_interpreter_entry(_masm, iid);
250 }
252 if (iid == vmIntrinsics::_invokeBasic) {
253 generate_method_handle_dispatch(_masm, iid, tmp_mh, noreg, not_for_compiler_entry);
255 } else {
256 // Adjust argument list by popping the trailing MemberName argument.
257 Register tmp_recv = noreg;
258 if (MethodHandles::ref_kind_has_receiver(ref_kind)) {
259 // Load the receiver (not the MH; the actual MemberName's receiver) up from the interpreter stack.
260 __ ld(tmp_recv = temp1, __ argument_offset(param_size, param_size, 0), argbase);
261 DEBUG_ONLY(param_size = noreg);
262 }
263 Register R19_member = R19_method; // MemberName ptr; incoming method ptr is dead now
264 __ ld(R19_member, RegisterOrConstant((intptr_t)8), argbase);
265 __ add(argbase, Interpreter::stackElementSize, argbase);
266 generate_method_handle_dispatch(_masm, iid, tmp_recv, R19_member, not_for_compiler_entry);
267 }
269 return entry_point;
270 }
272 void MethodHandles::generate_method_handle_dispatch(MacroAssembler* _masm,
273 vmIntrinsics::ID iid,
274 Register receiver_reg,
275 Register member_reg,
276 bool for_compiler_entry) {
277 assert(is_signature_polymorphic(iid), "expected invoke iid");
278 Register temp1 = (for_compiler_entry ? R25_tmp5 : R7);
279 Register temp2 = (for_compiler_entry ? R22_tmp2 : R8);
280 Register temp3 = (for_compiler_entry ? R23_tmp3 : R9);
281 Register temp4 = (for_compiler_entry ? R24_tmp4 : R10);
282 if (receiver_reg != noreg) assert_different_registers(temp1, temp2, temp3, temp4, receiver_reg);
283 if (member_reg != noreg) assert_different_registers(temp1, temp2, temp3, temp4, member_reg);
285 if (iid == vmIntrinsics::_invokeBasic) {
286 // indirect through MH.form.vmentry.vmtarget
287 jump_to_lambda_form(_masm, receiver_reg, R19_method, temp1, temp2, for_compiler_entry);
288 } else {
289 // The method is a member invoker used by direct method handles.
290 if (VerifyMethodHandles) {
291 // make sure the trailing argument really is a MemberName (caller responsibility)
292 verify_klass(_masm, member_reg, SystemDictionary::WK_KLASS_ENUM_NAME(MemberName_klass),
293 temp1, temp2,
294 "MemberName required for invokeVirtual etc.");
295 }
297 Register temp1_recv_klass = temp1;
298 if (iid != vmIntrinsics::_linkToStatic) {
299 __ verify_oop(receiver_reg);
300 if (iid == vmIntrinsics::_linkToSpecial) {
301 // Don't actually load the klass; just null-check the receiver.
302 __ null_check_throw(receiver_reg, -1, temp1, EXCEPTION_ENTRY);
303 } else {
304 // load receiver klass itself
305 __ null_check_throw(receiver_reg, oopDesc::klass_offset_in_bytes(), temp1, EXCEPTION_ENTRY);
306 __ load_klass(temp1_recv_klass, receiver_reg);
307 __ verify_klass_ptr(temp1_recv_klass);
308 }
309 BLOCK_COMMENT("check_receiver {");
310 // The receiver for the MemberName must be in receiver_reg.
311 // Check the receiver against the MemberName.clazz
312 if (VerifyMethodHandles && iid == vmIntrinsics::_linkToSpecial) {
313 // Did not load it above...
314 __ load_klass(temp1_recv_klass, receiver_reg);
315 __ verify_klass_ptr(temp1_recv_klass);
316 }
317 if (VerifyMethodHandles && iid != vmIntrinsics::_linkToInterface) {
318 Label L_ok;
319 Register temp2_defc = temp2;
320 __ load_heap_oop_not_null(temp2_defc, NONZERO(java_lang_invoke_MemberName::clazz_offset_in_bytes()), member_reg);
321 load_klass_from_Class(_masm, temp2_defc, temp3, temp4);
322 __ verify_klass_ptr(temp2_defc);
323 __ check_klass_subtype(temp1_recv_klass, temp2_defc, temp3, temp4, L_ok);
324 // If we get here, the type check failed!
325 __ stop("receiver class disagrees with MemberName.clazz");
326 __ BIND(L_ok);
327 }
328 BLOCK_COMMENT("} check_receiver");
329 }
330 if (iid == vmIntrinsics::_linkToSpecial ||
331 iid == vmIntrinsics::_linkToStatic) {
332 DEBUG_ONLY(temp1_recv_klass = noreg); // these guys didn't load the recv_klass
333 }
335 // Live registers at this point:
336 // member_reg - MemberName that was the trailing argument
337 // temp1_recv_klass - klass of stacked receiver, if needed
338 // O5_savedSP - interpreter linkage (if interpreted)
339 // O0..O5 - compiler arguments (if compiled)
341 Label L_incompatible_class_change_error;
342 switch (iid) {
343 case vmIntrinsics::_linkToSpecial:
344 if (VerifyMethodHandles) {
345 verify_ref_kind(_masm, JVM_REF_invokeSpecial, member_reg, temp2);
346 }
347 __ ld(R19_method, NONZERO(java_lang_invoke_MemberName::vmtarget_offset_in_bytes()), member_reg);
348 break;
350 case vmIntrinsics::_linkToStatic:
351 if (VerifyMethodHandles) {
352 verify_ref_kind(_masm, JVM_REF_invokeStatic, member_reg, temp2);
353 }
354 __ ld(R19_method, NONZERO(java_lang_invoke_MemberName::vmtarget_offset_in_bytes()), member_reg);
355 break;
357 case vmIntrinsics::_linkToVirtual:
358 {
359 // same as TemplateTable::invokevirtual,
360 // minus the CP setup and profiling:
362 if (VerifyMethodHandles) {
363 verify_ref_kind(_masm, JVM_REF_invokeVirtual, member_reg, temp2);
364 }
366 // pick out the vtable index from the MemberName, and then we can discard it:
367 Register temp2_index = temp2;
368 __ ld(temp2_index, NONZERO(java_lang_invoke_MemberName::vmindex_offset_in_bytes()), member_reg);
370 if (VerifyMethodHandles) {
371 Label L_index_ok;
372 __ cmpdi(CCR1, temp2_index, 0);
373 __ bge(CCR1, L_index_ok);
374 __ stop("no virtual index");
375 __ BIND(L_index_ok);
376 }
378 // Note: The verifier invariants allow us to ignore MemberName.clazz and vmtarget
379 // at this point. And VerifyMethodHandles has already checked clazz, if needed.
381 // get target Method* & entry point
382 __ lookup_virtual_method(temp1_recv_klass, temp2_index, R19_method);
383 break;
384 }
386 case vmIntrinsics::_linkToInterface:
387 {
388 // same as TemplateTable::invokeinterface
389 // (minus the CP setup and profiling, with different argument motion)
390 if (VerifyMethodHandles) {
391 verify_ref_kind(_masm, JVM_REF_invokeInterface, member_reg, temp2);
392 }
394 Register temp2_intf = temp2;
395 __ load_heap_oop_not_null(temp2_intf, NONZERO(java_lang_invoke_MemberName::clazz_offset_in_bytes()), member_reg);
396 load_klass_from_Class(_masm, temp2_intf, temp3, temp4);
397 __ verify_klass_ptr(temp2_intf);
399 Register vtable_index = R19_method;
400 __ ld(vtable_index, NONZERO(java_lang_invoke_MemberName::vmindex_offset_in_bytes()), member_reg);
401 if (VerifyMethodHandles) {
402 Label L_index_ok;
403 __ cmpdi(CCR1, vtable_index, 0);
404 __ bge(CCR1, L_index_ok);
405 __ stop("invalid vtable index for MH.invokeInterface");
406 __ BIND(L_index_ok);
407 }
409 // given intf, index, and recv klass, dispatch to the implementation method
410 __ lookup_interface_method(temp1_recv_klass, temp2_intf,
411 // note: next two args must be the same:
412 vtable_index, R19_method,
413 temp3, temp4,
414 L_incompatible_class_change_error);
415 break;
416 }
418 default:
419 fatal(err_msg_res("unexpected intrinsic %d: %s", iid, vmIntrinsics::name_at(iid)));
420 break;
421 }
423 // Live at this point:
424 // R19_method
425 // O5_savedSP (if interpreted)
427 // After figuring out which concrete method to call, jump into it.
428 // Note that this works in the interpreter with no data motion.
429 // But the compiled version will require that rcx_recv be shifted out.
430 __ verify_method_ptr(R19_method);
431 jump_from_method_handle(_masm, R19_method, temp1, temp2, for_compiler_entry);
433 if (iid == vmIntrinsics::_linkToInterface) {
434 __ BIND(L_incompatible_class_change_error);
435 __ load_const_optimized(temp1, StubRoutines::throw_IncompatibleClassChangeError_entry());
436 __ mtctr(temp1);
437 __ bctr();
438 }
439 }
440 }
442 #ifndef PRODUCT
443 void trace_method_handle_stub(const char* adaptername,
444 oopDesc* mh,
445 intptr_t* entry_sp,
446 intptr_t* saved_regs) {
448 bool has_mh = (strstr(adaptername, "/static") == NULL &&
449 strstr(adaptername, "linkTo") == NULL); // static linkers don't have MH
450 const char* mh_reg_name = has_mh ? "R23_method_handle" : "G23";
451 tty->print_cr("MH %s %s="INTPTR_FORMAT " sp=" INTPTR_FORMAT,
452 adaptername, mh_reg_name, (intptr_t) mh, entry_sp);
454 if (Verbose) {
455 tty->print_cr("Registers:");
456 const int abi_offset = frame::abi_reg_args_size / 8;
457 for (int i = R3->encoding(); i <= R12->encoding(); i++) {
458 Register r = as_Register(i);
459 int count = i - R3->encoding();
460 // The registers are stored in reverse order on the stack (by save_volatile_gprs(R1_SP, abi_reg_args_size)).
461 tty->print("%3s=" PTR_FORMAT, r->name(), saved_regs[abi_offset + count]);
462 if ((count + 1) % 4 == 0) {
463 tty->cr();
464 } else {
465 tty->print(", ");
466 }
467 }
468 tty->cr();
470 {
471 // dumping last frame with frame::describe
473 JavaThread* p = JavaThread::active();
475 ResourceMark rm;
476 PRESERVE_EXCEPTION_MARK; // may not be needed by safer and unexpensive here
477 FrameValues values;
479 // Note: We want to allow trace_method_handle from any call site.
480 // While trace_method_handle creates a frame, it may be entered
481 // without a PC on the stack top (e.g. not just after a call).
482 // Walking that frame could lead to failures due to that invalid PC.
483 // => carefully detect that frame when doing the stack walking
485 // Current C frame
486 frame cur_frame = os::current_frame();
488 // Robust search of trace_calling_frame (independant of inlining).
489 // Assumes saved_regs comes from a pusha in the trace_calling_frame.
490 assert(cur_frame.sp() < saved_regs, "registers not saved on stack ?");
491 frame trace_calling_frame = os::get_sender_for_C_frame(&cur_frame);
492 while (trace_calling_frame.fp() < saved_regs) {
493 trace_calling_frame = os::get_sender_for_C_frame(&trace_calling_frame);
494 }
496 // Safely create a frame and call frame::describe.
497 intptr_t *dump_sp = trace_calling_frame.sender_sp();
499 frame dump_frame = frame(dump_sp);
500 dump_frame.describe(values, 1);
502 values.describe(-1, saved_regs, "raw top of stack");
504 tty->print_cr("Stack layout:");
505 values.print(p);
506 }
508 if (has_mh && mh->is_oop()) {
509 mh->print();
510 if (java_lang_invoke_MethodHandle::is_instance(mh)) {
511 if (java_lang_invoke_MethodHandle::form_offset_in_bytes() != 0)
512 java_lang_invoke_MethodHandle::form(mh)->print();
513 }
514 }
515 }
516 }
518 void MethodHandles::trace_method_handle(MacroAssembler* _masm, const char* adaptername) {
519 if (!TraceMethodHandles) return;
521 BLOCK_COMMENT("trace_method_handle {");
523 int nbytes_save = 10 * 8; // 10 volatile gprs
524 __ save_LR_CR(R0);
525 __ mr(R0, R1_SP); // saved_sp
526 assert(Assembler::is_simm(-nbytes_save, 16), "Overwriting R0");
527 // Push_frame_reg_args only uses R0 if nbytes_save is wider than 16 bit.
528 __ push_frame_reg_args(nbytes_save, R0);
529 __ save_volatile_gprs(R1_SP, frame::abi_reg_args_size); // Except R0.
531 __ load_const(R3_ARG1, (address)adaptername);
532 __ mr(R4_ARG2, R23_method_handle);
533 __ mr(R5_ARG3, R0); // saved_sp
534 __ mr(R6_ARG4, R1_SP);
535 __ call_VM_leaf(CAST_FROM_FN_PTR(address, trace_method_handle_stub));
537 __ restore_volatile_gprs(R1_SP, 112); // Except R0.
538 __ pop_frame();
539 __ restore_LR_CR(R0);
541 BLOCK_COMMENT("} trace_method_handle");
542 }
543 #endif // PRODUCT