1 /* 2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "asm/macroAssembler.hpp" 27 #include "asm/macroAssembler.inline.hpp" 28 #include "asm/codeBuffer.hpp" 29 #include "runtime/atomic.inline.hpp" 30 #include "runtime/icache.hpp" 31 #include "runtime/os.hpp" 32 33 34 // Implementation of AbstractAssembler 35 // 36 // The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster, 37 // the assembler keeps a copy of the code buffers boundaries & modifies them when 38 // emitting bytes rather than using the code buffers accessor functions all the time. 39 // The code buffer is updated via set_code_end(...) after emitting a whole instruction. 40 41 AbstractAssembler::AbstractAssembler(CodeBuffer* code) { 42 if (code == NULL) return; 43 CodeSection* cs = code->insts(); 44 cs->clear_mark(); // new assembler kills old mark 45 if (cs->start() == NULL) { 46 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "CodeCache: no room for %s", code->name()); 47 } 48 _code_section = cs; 49 _oop_recorder= code->oop_recorder(); 50 DEBUG_ONLY( _short_branch_delta = 0; ) 51 } 52 53 void AbstractAssembler::set_code_section(CodeSection* cs) { 54 assert(cs->outer() == code_section()->outer(), "sanity"); 55 assert(cs->is_allocated(), "need to pre-allocate this section"); 56 cs->clear_mark(); // new assembly into this section kills old mark 57 _code_section = cs; 58 } 59 60 // Inform CodeBuffer that incoming code and relocation will be for stubs 61 address AbstractAssembler::start_a_stub(int required_space) { 62 CodeBuffer* cb = code(); 63 CodeSection* cs = cb->stubs(); 64 assert(_code_section == cb->insts(), "not in insts?"); 65 if (cs->maybe_expand_to_ensure_remaining(required_space) 66 && cb->blob() == NULL) { 67 return NULL; 68 } 69 set_code_section(cs); 70 return pc(); 71 } 72 73 // Inform CodeBuffer that incoming code and relocation will be code 74 // Should not be called if start_a_stub() returned NULL 75 void AbstractAssembler::end_a_stub() { 76 assert(_code_section == code()->stubs(), "not in stubs?"); 77 set_code_section(code()->insts()); 78 } 79 80 // Inform CodeBuffer that incoming code and relocation will be for stubs 81 address AbstractAssembler::start_a_const(int required_space, int required_align) { 82 CodeBuffer* cb = code(); 83 CodeSection* cs = cb->consts(); 84 assert(_code_section == cb->insts() || _code_section == cb->stubs(), "not in insts/stubs?"); 85 address end = cs->end(); 86 int pad = -(intptr_t)end & (required_align-1); 87 if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) { 88 if (cb->blob() == NULL) return NULL; 89 end = cs->end(); // refresh pointer 90 } 91 if (pad > 0) { 92 while (--pad >= 0) { *end++ = 0; } 93 cs->set_end(end); 94 } 95 set_code_section(cs); 96 return end; 97 } 98 99 // Inform CodeBuffer that incoming code and relocation will be code 100 // in section cs (insts or stubs). 101 void AbstractAssembler::end_a_const(CodeSection* cs) { 102 assert(_code_section == code()->consts(), "not in consts?"); 103 set_code_section(cs); 104 } 105 106 void AbstractAssembler::flush() { 107 ICache::invalidate_range(addr_at(0), offset()); 108 } 109 110 void AbstractAssembler::bind(Label& L) { 111 if (L.is_bound()) { 112 // Assembler can bind a label more than once to the same place. 113 guarantee(L.loc() == locator(), "attempt to redefine label"); 114 return; 115 } 116 L.bind_loc(locator()); 117 L.patch_instructions((MacroAssembler*)this); 118 } 119 120 void AbstractAssembler::generate_stack_overflow_check(int frame_size_in_bytes) { 121 if (UseStackBanging) { 122 // Each code entry causes one stack bang n pages down the stack where n 123 // is configurable by StackShadowPages. The setting depends on the maximum 124 // depth of VM call stack or native before going back into java code, 125 // since only java code can raise a stack overflow exception using the 126 // stack banging mechanism. The VM and native code does not detect stack 127 // overflow. 128 // The code in JavaCalls::call() checks that there is at least n pages 129 // available, so all entry code needs to do is bang once for the end of 130 // this shadow zone. 131 // The entry code may need to bang additional pages if the framesize 132 // is greater than a page. 133 134 const int page_size = os::vm_page_size(); 135 int bang_end = StackShadowPages * page_size; 136 137 // This is how far the previous frame's stack banging extended. 138 const int bang_end_safe = bang_end; 139 140 if (frame_size_in_bytes > page_size) { 141 bang_end += frame_size_in_bytes; 142 } 143 144 int bang_offset = bang_end_safe; 145 while (bang_offset <= bang_end) { 146 // Need at least one stack bang at end of shadow zone. 147 bang_stack_with_offset(bang_offset); 148 bang_offset += page_size; 149 } 150 } // end (UseStackBanging) 151 } 152 153 void Label::add_patch_at(CodeBuffer* cb, int branch_loc) { 154 assert(_loc == -1, "Label is unbound"); 155 if (_patch_index < PatchCacheSize) { 156 _patches[_patch_index] = branch_loc; 157 } else { 158 if (_patch_overflow == NULL) { 159 _patch_overflow = cb->create_patch_overflow(); 160 } 161 _patch_overflow->push(branch_loc); 162 } 163 ++_patch_index; 164 } 165 166 void Label::patch_instructions(MacroAssembler* masm) { 167 assert(is_bound(), "Label is bound"); 168 CodeBuffer* cb = masm->code(); 169 int target_sect = CodeBuffer::locator_sect(loc()); 170 address target = cb->locator_address(loc()); 171 while (_patch_index > 0) { 172 --_patch_index; 173 int branch_loc; 174 if (_patch_index >= PatchCacheSize) { 175 branch_loc = _patch_overflow->pop(); 176 } else { 177 branch_loc = _patches[_patch_index]; 178 } 179 int branch_sect = CodeBuffer::locator_sect(branch_loc); 180 address branch = cb->locator_address(branch_loc); 181 if (branch_sect == CodeBuffer::SECT_CONSTS) { 182 // The thing to patch is a constant word. 183 *(address*)branch = target; 184 continue; 185 } 186 187 #ifdef ASSERT 188 // Cross-section branches only work if the 189 // intermediate section boundaries are frozen. 190 if (target_sect != branch_sect) { 191 for (int n = MIN2(target_sect, branch_sect), 192 nlimit = (target_sect + branch_sect) - n; 193 n < nlimit; n++) { 194 CodeSection* cs = cb->code_section(n); 195 assert(cs->is_frozen(), "cross-section branch needs stable offsets"); 196 } 197 } 198 #endif //ASSERT 199 200 // Push the target offset into the branch instruction. 201 masm->pd_patch_instruction(branch, target); 202 } 203 } 204 205 struct DelayedConstant { 206 typedef void (*value_fn_t)(); 207 BasicType type; 208 intptr_t value; 209 value_fn_t value_fn; 210 // This limit of 20 is generous for initial uses. 211 // The limit needs to be large enough to store the field offsets 212 // into classes which do not have statically fixed layouts. 213 // (Initial use is for method handle object offsets.) 214 // Look for uses of "delayed_value" in the source code 215 // and make sure this number is generous enough to handle all of them. 216 enum { DC_LIMIT = 20 }; 217 static DelayedConstant delayed_constants[DC_LIMIT]; 218 static DelayedConstant* add(BasicType type, value_fn_t value_fn); 219 bool match(BasicType t, value_fn_t cfn) { 220 return type == t && value_fn == cfn; 221 } 222 static void update_all(); 223 }; 224 225 DelayedConstant DelayedConstant::delayed_constants[DC_LIMIT]; 226 // Default C structure initialization rules have the following effect here: 227 // = { { (BasicType)0, (intptr_t)NULL }, ... }; 228 229 DelayedConstant* DelayedConstant::add(BasicType type, 230 DelayedConstant::value_fn_t cfn) { 231 for (int i = 0; i < DC_LIMIT; i++) { 232 DelayedConstant* dcon = &delayed_constants[i]; 233 if (dcon->match(type, cfn)) 234 return dcon; 235 if (dcon->value_fn == NULL) { 236 // (cmpxchg not because this is multi-threaded but because I'm paranoid) 237 if (Atomic::cmpxchg_ptr(CAST_FROM_FN_PTR(void*, cfn), &dcon->value_fn, NULL) == NULL) { 238 dcon->type = type; 239 return dcon; 240 } 241 } 242 } 243 // If this assert is hit (in pre-integration testing!) then re-evaluate 244 // the comment on the definition of DC_LIMIT. 245 guarantee(false, "too many delayed constants"); 246 return NULL; 247 } 248 249 void DelayedConstant::update_all() { 250 for (int i = 0; i < DC_LIMIT; i++) { 251 DelayedConstant* dcon = &delayed_constants[i]; 252 if (dcon->value_fn != NULL && dcon->value == 0) { 253 typedef int (*int_fn_t)(); 254 typedef address (*address_fn_t)(); 255 switch (dcon->type) { 256 case T_INT: dcon->value = (intptr_t) ((int_fn_t) dcon->value_fn)(); break; 257 case T_ADDRESS: dcon->value = (intptr_t) ((address_fn_t)dcon->value_fn)(); break; 258 } 259 } 260 } 261 } 262 263 RegisterOrConstant AbstractAssembler::delayed_value(int(*value_fn)(), Register tmp, int offset) { 264 intptr_t val = (intptr_t) (*value_fn)(); 265 if (val != 0) return val + offset; 266 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset); 267 } 268 RegisterOrConstant AbstractAssembler::delayed_value(address(*value_fn)(), Register tmp, int offset) { 269 intptr_t val = (intptr_t) (*value_fn)(); 270 if (val != 0) return val + offset; 271 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset); 272 } 273 intptr_t* AbstractAssembler::delayed_value_addr(int(*value_fn)()) { 274 DelayedConstant* dcon = DelayedConstant::add(T_INT, (DelayedConstant::value_fn_t) value_fn); 275 return &dcon->value; 276 } 277 intptr_t* AbstractAssembler::delayed_value_addr(address(*value_fn)()) { 278 DelayedConstant* dcon = DelayedConstant::add(T_ADDRESS, (DelayedConstant::value_fn_t) value_fn); 279 return &dcon->value; 280 } 281 void AbstractAssembler::update_delayed_values() { 282 DelayedConstant::update_all(); 283 } 284 285 void AbstractAssembler::block_comment(const char* comment) { 286 if (sect() == CodeBuffer::SECT_INSTS) { 287 code_section()->outer()->block_comment(offset(), comment); 288 } 289 } 290 291 const char* AbstractAssembler::code_string(const char* str) { 292 if (sect() == CodeBuffer::SECT_INSTS || sect() == CodeBuffer::SECT_STUBS) { 293 return code_section()->outer()->code_string(str); 294 } 295 return NULL; 296 } 297 298 bool MacroAssembler::needs_explicit_null_check(intptr_t offset) { 299 // Exception handler checks the nmethod's implicit null checks table 300 // only when this method returns false. 301 #ifdef _LP64 302 if (UseCompressedOops && Universe::narrow_oop_base() != NULL) { 303 assert (Universe::heap() != NULL, "java heap should be initialized"); 304 // The first page after heap_base is unmapped and 305 // the 'offset' is equal to [heap_base + offset] for 306 // narrow oop implicit null checks. 307 uintptr_t base = (uintptr_t)Universe::narrow_oop_base(); 308 if ((uintptr_t)offset >= base) { 309 // Normalize offset for the next check. 310 offset = (intptr_t)(pointer_delta((void*)offset, (void*)base, 1)); 311 } 312 } 313 #endif 314 return offset < 0 || os::vm_page_size() <= offset; 315 }