1 /*
   2  * Copyright (c) 1997, 2014, 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 "memory/resourceArea.hpp"
  29 #include "runtime/java.hpp"
  30 #include "runtime/os.hpp"
  31 #include "runtime/stubCodeGenerator.hpp"
  32 #include "vm_version_x86.hpp"
  33 
  34 
  35 int VM_Version::_cpu;
  36 int VM_Version::_model;
  37 int VM_Version::_stepping;
  38 int VM_Version::_cpuFeatures;
  39 const char*           VM_Version::_features_str = "";
  40 VM_Version::CpuidInfo VM_Version::_cpuid_info   = { 0, };
  41 
  42 // Address of instruction which causes SEGV
  43 address VM_Version::_cpuinfo_segv_addr = 0;
  44 // Address of instruction after the one which causes SEGV
  45 address VM_Version::_cpuinfo_cont_addr = 0;
  46 
  47 static BufferBlob* stub_blob;
  48 static const int stub_size = 600;
  49 
  50 extern "C" {
  51   typedef void (*get_cpu_info_stub_t)(void*);
  52 }
  53 static get_cpu_info_stub_t get_cpu_info_stub = NULL;
  54 
  55 
  56 class VM_Version_StubGenerator: public StubCodeGenerator {
  57  public:
  58 
  59   VM_Version_StubGenerator(CodeBuffer *c) : StubCodeGenerator(c) {}
  60 
  61   address generate_get_cpu_info() {
  62     // Flags to test CPU type.
  63     const uint32_t HS_EFL_AC           = 0x40000;
  64     const uint32_t HS_EFL_ID           = 0x200000;
  65     // Values for when we don't have a CPUID instruction.
  66     const int      CPU_FAMILY_SHIFT = 8;
  67     const uint32_t CPU_FAMILY_386   = (3 << CPU_FAMILY_SHIFT);
  68     const uint32_t CPU_FAMILY_486   = (4 << CPU_FAMILY_SHIFT);
  69 
  70     Label detect_486, cpu486, detect_586, std_cpuid1, std_cpuid4;
  71     Label sef_cpuid, ext_cpuid, ext_cpuid1, ext_cpuid5, ext_cpuid7, done;
  72 
  73     StubCodeMark mark(this, "VM_Version", "get_cpu_info_stub");
  74 #   define __ _masm->
  75 
  76     address start = __ pc();
  77 
  78     //
  79     // void get_cpu_info(VM_Version::CpuidInfo* cpuid_info);
  80     //
  81     // LP64: rcx and rdx are first and second argument registers on windows
  82 
  83     __ push(rbp);
  84 #ifdef _LP64
  85     __ mov(rbp, c_rarg0); // cpuid_info address
  86 #else
  87     __ movptr(rbp, Address(rsp, 8)); // cpuid_info address
  88 #endif
  89     __ push(rbx);
  90     __ push(rsi);
  91     __ pushf();          // preserve rbx, and flags
  92     __ pop(rax);
  93     __ push(rax);
  94     __ mov(rcx, rax);
  95     //
  96     // if we are unable to change the AC flag, we have a 386
  97     //
  98     __ xorl(rax, HS_EFL_AC);
  99     __ push(rax);
 100     __ popf();
 101     __ pushf();
 102     __ pop(rax);
 103     __ cmpptr(rax, rcx);
 104     __ jccb(Assembler::notEqual, detect_486);
 105 
 106     __ movl(rax, CPU_FAMILY_386);
 107     __ movl(Address(rbp, in_bytes(VM_Version::std_cpuid1_offset())), rax);
 108     __ jmp(done);
 109 
 110     //
 111     // If we are unable to change the ID flag, we have a 486 which does
 112     // not support the "cpuid" instruction.
 113     //
 114     __ bind(detect_486);
 115     __ mov(rax, rcx);
 116     __ xorl(rax, HS_EFL_ID);
 117     __ push(rax);
 118     __ popf();
 119     __ pushf();
 120     __ pop(rax);
 121     __ cmpptr(rcx, rax);
 122     __ jccb(Assembler::notEqual, detect_586);
 123 
 124     __ bind(cpu486);
 125     __ movl(rax, CPU_FAMILY_486);
 126     __ movl(Address(rbp, in_bytes(VM_Version::std_cpuid1_offset())), rax);
 127     __ jmp(done);
 128 
 129     //
 130     // At this point, we have a chip which supports the "cpuid" instruction
 131     //
 132     __ bind(detect_586);
 133     __ xorl(rax, rax);
 134     __ cpuid();
 135     __ orl(rax, rax);
 136     __ jcc(Assembler::equal, cpu486);   // if cpuid doesn't support an input
 137                                         // value of at least 1, we give up and
 138                                         // assume a 486
 139     __ lea(rsi, Address(rbp, in_bytes(VM_Version::std_cpuid0_offset())));
 140     __ movl(Address(rsi, 0), rax);
 141     __ movl(Address(rsi, 4), rbx);
 142     __ movl(Address(rsi, 8), rcx);
 143     __ movl(Address(rsi,12), rdx);
 144 
 145     __ cmpl(rax, 0xa);                  // Is cpuid(0xB) supported?
 146     __ jccb(Assembler::belowEqual, std_cpuid4);
 147 
 148     //
 149     // cpuid(0xB) Processor Topology
 150     //
 151     __ movl(rax, 0xb);
 152     __ xorl(rcx, rcx);   // Threads level
 153     __ cpuid();
 154 
 155     __ lea(rsi, Address(rbp, in_bytes(VM_Version::tpl_cpuidB0_offset())));
 156     __ movl(Address(rsi, 0), rax);
 157     __ movl(Address(rsi, 4), rbx);
 158     __ movl(Address(rsi, 8), rcx);
 159     __ movl(Address(rsi,12), rdx);
 160 
 161     __ movl(rax, 0xb);
 162     __ movl(rcx, 1);     // Cores level
 163     __ cpuid();
 164     __ push(rax);
 165     __ andl(rax, 0x1f);  // Determine if valid topology level
 166     __ orl(rax, rbx);    // eax[4:0] | ebx[0:15] == 0 indicates invalid level
 167     __ andl(rax, 0xffff);
 168     __ pop(rax);
 169     __ jccb(Assembler::equal, std_cpuid4);
 170 
 171     __ lea(rsi, Address(rbp, in_bytes(VM_Version::tpl_cpuidB1_offset())));
 172     __ movl(Address(rsi, 0), rax);
 173     __ movl(Address(rsi, 4), rbx);
 174     __ movl(Address(rsi, 8), rcx);
 175     __ movl(Address(rsi,12), rdx);
 176 
 177     __ movl(rax, 0xb);
 178     __ movl(rcx, 2);     // Packages level
 179     __ cpuid();
 180     __ push(rax);
 181     __ andl(rax, 0x1f);  // Determine if valid topology level
 182     __ orl(rax, rbx);    // eax[4:0] | ebx[0:15] == 0 indicates invalid level
 183     __ andl(rax, 0xffff);
 184     __ pop(rax);
 185     __ jccb(Assembler::equal, std_cpuid4);
 186 
 187     __ lea(rsi, Address(rbp, in_bytes(VM_Version::tpl_cpuidB2_offset())));
 188     __ movl(Address(rsi, 0), rax);
 189     __ movl(Address(rsi, 4), rbx);
 190     __ movl(Address(rsi, 8), rcx);
 191     __ movl(Address(rsi,12), rdx);
 192 
 193     //
 194     // cpuid(0x4) Deterministic cache params
 195     //
 196     __ bind(std_cpuid4);
 197     __ movl(rax, 4);
 198     __ cmpl(rax, Address(rbp, in_bytes(VM_Version::std_cpuid0_offset()))); // Is cpuid(0x4) supported?
 199     __ jccb(Assembler::greater, std_cpuid1);
 200 
 201     __ xorl(rcx, rcx);   // L1 cache
 202     __ cpuid();
 203     __ push(rax);
 204     __ andl(rax, 0x1f);  // Determine if valid cache parameters used
 205     __ orl(rax, rax);    // eax[4:0] == 0 indicates invalid cache
 206     __ pop(rax);
 207     __ jccb(Assembler::equal, std_cpuid1);
 208 
 209     __ lea(rsi, Address(rbp, in_bytes(VM_Version::dcp_cpuid4_offset())));
 210     __ movl(Address(rsi, 0), rax);
 211     __ movl(Address(rsi, 4), rbx);
 212     __ movl(Address(rsi, 8), rcx);
 213     __ movl(Address(rsi,12), rdx);
 214 
 215     //
 216     // Standard cpuid(0x1)
 217     //
 218     __ bind(std_cpuid1);
 219     __ movl(rax, 1);
 220     __ cpuid();
 221     __ lea(rsi, Address(rbp, in_bytes(VM_Version::std_cpuid1_offset())));
 222     __ movl(Address(rsi, 0), rax);
 223     __ movl(Address(rsi, 4), rbx);
 224     __ movl(Address(rsi, 8), rcx);
 225     __ movl(Address(rsi,12), rdx);
 226 
 227     //
 228     // Check if OS has enabled XGETBV instruction to access XCR0
 229     // (OSXSAVE feature flag) and CPU supports AVX
 230     //
 231     __ andl(rcx, 0x18000000); // cpuid1 bits osxsave | avx
 232     __ cmpl(rcx, 0x18000000);
 233     __ jccb(Assembler::notEqual, sef_cpuid); // jump if AVX is not supported
 234 
 235     //
 236     // XCR0, XFEATURE_ENABLED_MASK register
 237     //
 238     __ xorl(rcx, rcx);   // zero for XCR0 register
 239     __ xgetbv();
 240     __ lea(rsi, Address(rbp, in_bytes(VM_Version::xem_xcr0_offset())));
 241     __ movl(Address(rsi, 0), rax);
 242     __ movl(Address(rsi, 4), rdx);
 243 
 244     __ andl(rax, 0x6); // xcr0 bits sse | ymm
 245     __ cmpl(rax, 0x6);
 246     __ jccb(Assembler::notEqual, sef_cpuid); // jump if AVX is not supported
 247 
 248     //
 249     // Some OSs have a bug when upper 128bits of YMM
 250     // registers are not restored after a signal processing.
 251     // Generate SEGV here (reference through NULL)
 252     // and check upper YMM bits after it.
 253     //
 254     VM_Version::set_avx_cpuFeatures(); // Enable temporary to pass asserts
 255     intx saved_useavx = UseAVX;
 256     intx saved_usesse = UseSSE;
 257     UseAVX = 1;
 258     UseSSE = 2;
 259 
 260     // load value into all 32 bytes of ymm7 register
 261     __ movl(rcx, VM_Version::ymm_test_value());
 262 
 263     __ movdl(xmm0, rcx);
 264     __ pshufd(xmm0, xmm0, 0x00);
 265     __ vinsertf128h(xmm0, xmm0, xmm0);
 266     __ vmovdqu(xmm7, xmm0);
 267 #ifdef _LP64
 268     __ vmovdqu(xmm8,  xmm0);
 269     __ vmovdqu(xmm15, xmm0);
 270 #endif
 271 
 272     __ xorl(rsi, rsi);
 273     VM_Version::set_cpuinfo_segv_addr( __ pc() );
 274     // Generate SEGV
 275     __ movl(rax, Address(rsi, 0));
 276 
 277     VM_Version::set_cpuinfo_cont_addr( __ pc() );
 278     // Returns here after signal. Save xmm0 to check it later.
 279     __ lea(rsi, Address(rbp, in_bytes(VM_Version::ymm_save_offset())));
 280     __ vmovdqu(Address(rsi,  0), xmm0);
 281     __ vmovdqu(Address(rsi, 32), xmm7);
 282 #ifdef _LP64
 283     __ vmovdqu(Address(rsi, 64), xmm8);
 284     __ vmovdqu(Address(rsi, 96), xmm15);
 285 #endif
 286 
 287     VM_Version::clean_cpuFeatures();
 288     UseAVX = saved_useavx;
 289     UseSSE = saved_usesse;
 290 
 291     //
 292     // cpuid(0x7) Structured Extended Features
 293     //
 294     __ bind(sef_cpuid);
 295     __ movl(rax, 7);
 296     __ cmpl(rax, Address(rbp, in_bytes(VM_Version::std_cpuid0_offset()))); // Is cpuid(0x7) supported?
 297     __ jccb(Assembler::greater, ext_cpuid);
 298 
 299     __ xorl(rcx, rcx);
 300     __ cpuid();
 301     __ lea(rsi, Address(rbp, in_bytes(VM_Version::sef_cpuid7_offset())));
 302     __ movl(Address(rsi, 0), rax);
 303     __ movl(Address(rsi, 4), rbx);
 304 
 305     //
 306     // Extended cpuid(0x80000000)
 307     //
 308     __ bind(ext_cpuid);
 309     __ movl(rax, 0x80000000);
 310     __ cpuid();
 311     __ cmpl(rax, 0x80000000);     // Is cpuid(0x80000001) supported?
 312     __ jcc(Assembler::belowEqual, done);
 313     __ cmpl(rax, 0x80000004);     // Is cpuid(0x80000005) supported?
 314     __ jccb(Assembler::belowEqual, ext_cpuid1);
 315     __ cmpl(rax, 0x80000006);     // Is cpuid(0x80000007) supported?
 316     __ jccb(Assembler::belowEqual, ext_cpuid5);
 317     __ cmpl(rax, 0x80000007);     // Is cpuid(0x80000008) supported?
 318     __ jccb(Assembler::belowEqual, ext_cpuid7);
 319     //
 320     // Extended cpuid(0x80000008)
 321     //
 322     __ movl(rax, 0x80000008);
 323     __ cpuid();
 324     __ lea(rsi, Address(rbp, in_bytes(VM_Version::ext_cpuid8_offset())));
 325     __ movl(Address(rsi, 0), rax);
 326     __ movl(Address(rsi, 4), rbx);
 327     __ movl(Address(rsi, 8), rcx);
 328     __ movl(Address(rsi,12), rdx);
 329 
 330     //
 331     // Extended cpuid(0x80000007)
 332     //
 333     __ bind(ext_cpuid7);
 334     __ movl(rax, 0x80000007);
 335     __ cpuid();
 336     __ lea(rsi, Address(rbp, in_bytes(VM_Version::ext_cpuid7_offset())));
 337     __ movl(Address(rsi, 0), rax);
 338     __ movl(Address(rsi, 4), rbx);
 339     __ movl(Address(rsi, 8), rcx);
 340     __ movl(Address(rsi,12), rdx);
 341 
 342     //
 343     // Extended cpuid(0x80000005)
 344     //
 345     __ bind(ext_cpuid5);
 346     __ movl(rax, 0x80000005);
 347     __ cpuid();
 348     __ lea(rsi, Address(rbp, in_bytes(VM_Version::ext_cpuid5_offset())));
 349     __ movl(Address(rsi, 0), rax);
 350     __ movl(Address(rsi, 4), rbx);
 351     __ movl(Address(rsi, 8), rcx);
 352     __ movl(Address(rsi,12), rdx);
 353 
 354     //
 355     // Extended cpuid(0x80000001)
 356     //
 357     __ bind(ext_cpuid1);
 358     __ movl(rax, 0x80000001);
 359     __ cpuid();
 360     __ lea(rsi, Address(rbp, in_bytes(VM_Version::ext_cpuid1_offset())));
 361     __ movl(Address(rsi, 0), rax);
 362     __ movl(Address(rsi, 4), rbx);
 363     __ movl(Address(rsi, 8), rcx);
 364     __ movl(Address(rsi,12), rdx);
 365 
 366     //
 367     // return
 368     //
 369     __ bind(done);
 370     __ popf();
 371     __ pop(rsi);
 372     __ pop(rbx);
 373     __ pop(rbp);
 374     __ ret(0);
 375 
 376 #   undef __
 377 
 378     return start;
 379   };
 380 };
 381 
 382 
 383 void VM_Version::get_cpu_info_wrapper() {
 384   get_cpu_info_stub(&_cpuid_info);
 385 }
 386 
 387 #ifndef CALL_TEST_FUNC_WITH_WRAPPER_IF_NEEDED
 388   #define CALL_TEST_FUNC_WITH_WRAPPER_IF_NEEDED(f) f()
 389 #endif
 390 
 391 void VM_Version::get_processor_features() {
 392 
 393   _cpu = 4; // 486 by default
 394   _model = 0;
 395   _stepping = 0;
 396   _cpuFeatures = 0;
 397   _logical_processors_per_package = 1;
 398   // i486 internal cache is both I&D and has a 16-byte line size
 399   _L1_data_cache_line_size = 16;
 400 
 401   if (!Use486InstrsOnly) {
 402     // Get raw processor info
 403 
 404     // Some platforms (like Win*) need a wrapper around here
 405     // in order to properly handle SEGV for YMM registers test.
 406     CALL_TEST_FUNC_WITH_WRAPPER_IF_NEEDED(get_cpu_info_wrapper);
 407 
 408     assert_is_initialized();
 409     _cpu = extended_cpu_family();
 410     _model = extended_cpu_model();
 411     _stepping = cpu_stepping();
 412 
 413     if (cpu_family() > 4) { // it supports CPUID
 414       _cpuFeatures = feature_flags();
 415       // Logical processors are only available on P4s and above,
 416       // and only if hyperthreading is available.
 417       _logical_processors_per_package = logical_processor_count();
 418       _L1_data_cache_line_size = L1_line_size();
 419     }
 420   }
 421 
 422   _supports_cx8 = supports_cmpxchg8();
 423   // xchg and xadd instructions
 424   _supports_atomic_getset4 = true;
 425   _supports_atomic_getadd4 = true;
 426   LP64_ONLY(_supports_atomic_getset8 = true);
 427   LP64_ONLY(_supports_atomic_getadd8 = true);
 428 
 429 #ifdef _LP64
 430   // OS should support SSE for x64 and hardware should support at least SSE2.
 431   if (!VM_Version::supports_sse2()) {
 432     vm_exit_during_initialization("Unknown x64 processor: SSE2 not supported");
 433   }
 434   // in 64 bit the use of SSE2 is the minimum
 435   if (UseSSE < 2) UseSSE = 2;
 436 #endif
 437 
 438 #ifdef AMD64
 439   // flush_icache_stub have to be generated first.
 440   // That is why Icache line size is hard coded in ICache class,
 441   // see icache_x86.hpp. It is also the reason why we can't use
 442   // clflush instruction in 32-bit VM since it could be running
 443   // on CPU which does not support it.
 444   //
 445   // The only thing we can do is to verify that flushed
 446   // ICache::line_size has correct value.
 447   guarantee(_cpuid_info.std_cpuid1_edx.bits.clflush != 0, "clflush is not supported");
 448   // clflush_size is size in quadwords (8 bytes).
 449   guarantee(_cpuid_info.std_cpuid1_ebx.bits.clflush_size == 8, "such clflush size is not supported");
 450 #endif
 451 
 452   // If the OS doesn't support SSE, we can't use this feature even if the HW does
 453   if (!os::supports_sse())
 454     _cpuFeatures &= ~(CPU_SSE|CPU_SSE2|CPU_SSE3|CPU_SSSE3|CPU_SSE4A|CPU_SSE4_1|CPU_SSE4_2);
 455 
 456   if (UseSSE < 4) {
 457     _cpuFeatures &= ~CPU_SSE4_1;
 458     _cpuFeatures &= ~CPU_SSE4_2;
 459   }
 460 
 461   if (UseSSE < 3) {
 462     _cpuFeatures &= ~CPU_SSE3;
 463     _cpuFeatures &= ~CPU_SSSE3;
 464     _cpuFeatures &= ~CPU_SSE4A;
 465   }
 466 
 467   if (UseSSE < 2)
 468     _cpuFeatures &= ~CPU_SSE2;
 469 
 470   if (UseSSE < 1)
 471     _cpuFeatures &= ~CPU_SSE;
 472 
 473   if (UseAVX < 2)
 474     _cpuFeatures &= ~CPU_AVX2;
 475 
 476   if (UseAVX < 1)
 477     _cpuFeatures &= ~CPU_AVX;
 478 
 479   if (!UseAES && !FLAG_IS_DEFAULT(UseAES))
 480     _cpuFeatures &= ~CPU_AES;
 481 
 482   if (logical_processors_per_package() == 1) {
 483     // HT processor could be installed on a system which doesn't support HT.
 484     _cpuFeatures &= ~CPU_HT;
 485   }
 486 
 487   char buf[256];
 488   jio_snprintf(buf, sizeof(buf), "(%u cores per cpu, %u threads per core) family %d model %d stepping %d%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
 489                cores_per_cpu(), threads_per_core(),
 490                cpu_family(), _model, _stepping,
 491                (supports_cmov() ? ", cmov" : ""),
 492                (supports_cmpxchg8() ? ", cx8" : ""),
 493                (supports_fxsr() ? ", fxsr" : ""),
 494                (supports_mmx()  ? ", mmx"  : ""),
 495                (supports_sse()  ? ", sse"  : ""),
 496                (supports_sse2() ? ", sse2" : ""),
 497                (supports_sse3() ? ", sse3" : ""),
 498                (supports_ssse3()? ", ssse3": ""),
 499                (supports_sse4_1() ? ", sse4.1" : ""),
 500                (supports_sse4_2() ? ", sse4.2" : ""),
 501                (supports_popcnt() ? ", popcnt" : ""),
 502                (supports_avx()    ? ", avx" : ""),
 503                (supports_avx2()   ? ", avx2" : ""),
 504                (supports_aes()    ? ", aes" : ""),
 505                (supports_clmul()  ? ", clmul" : ""),
 506                (supports_erms()   ? ", erms" : ""),
 507                (supports_rtm()    ? ", rtm" : ""),
 508                (supports_mmx_ext() ? ", mmxext" : ""),
 509                (supports_3dnow_prefetch() ? ", 3dnowpref" : ""),
 510                (supports_lzcnt()   ? ", lzcnt": ""),
 511                (supports_sse4a()   ? ", sse4a": ""),
 512                (supports_ht() ? ", ht": ""),
 513                (supports_tsc() ? ", tsc": ""),
 514                (supports_tscinv_bit() ? ", tscinvbit": ""),
 515                (supports_tscinv() ? ", tscinv": ""),
 516                (supports_bmi1() ? ", bmi1" : ""),
 517                (supports_bmi2() ? ", bmi2" : ""),
 518                (supports_adx() ? ", adx" : ""));
 519   _features_str = os::strdup(buf);
 520 
 521   // UseSSE is set to the smaller of what hardware supports and what
 522   // the command line requires.  I.e., you cannot set UseSSE to 2 on
 523   // older Pentiums which do not support it.
 524   if (UseSSE > 4) UseSSE=4;
 525   if (UseSSE < 0) UseSSE=0;
 526   if (!supports_sse4_1()) // Drop to 3 if no SSE4 support
 527     UseSSE = MIN2((intx)3,UseSSE);
 528   if (!supports_sse3()) // Drop to 2 if no SSE3 support
 529     UseSSE = MIN2((intx)2,UseSSE);
 530   if (!supports_sse2()) // Drop to 1 if no SSE2 support
 531     UseSSE = MIN2((intx)1,UseSSE);
 532   if (!supports_sse ()) // Drop to 0 if no SSE  support
 533     UseSSE = 0;
 534 
 535   if (UseAVX > 2) UseAVX=2;
 536   if (UseAVX < 0) UseAVX=0;
 537   if (!supports_avx2()) // Drop to 1 if no AVX2 support
 538     UseAVX = MIN2((intx)1,UseAVX);
 539   if (!supports_avx ()) // Drop to 0 if no AVX  support
 540     UseAVX = 0;
 541 
 542   // Use AES instructions if available.
 543   if (supports_aes()) {
 544     if (FLAG_IS_DEFAULT(UseAES)) {
 545       UseAES = true;
 546     }
 547   } else if (UseAES) {
 548     if (!FLAG_IS_DEFAULT(UseAES))
 549       warning("AES instructions are not available on this CPU");
 550     FLAG_SET_DEFAULT(UseAES, false);
 551   }
 552 
 553   // Use CLMUL instructions if available.
 554   if (supports_clmul()) {
 555     if (FLAG_IS_DEFAULT(UseCLMUL)) {
 556       UseCLMUL = true;
 557     }
 558   } else if (UseCLMUL) {
 559     if (!FLAG_IS_DEFAULT(UseCLMUL))
 560       warning("CLMUL instructions not available on this CPU (AVX may also be required)");
 561     FLAG_SET_DEFAULT(UseCLMUL, false);
 562   }
 563 
 564   if (UseCLMUL && (UseSSE > 2)) {
 565     if (FLAG_IS_DEFAULT(UseCRC32Intrinsics)) {
 566       UseCRC32Intrinsics = true;
 567     }
 568   } else if (UseCRC32Intrinsics) {
 569     if (!FLAG_IS_DEFAULT(UseCRC32Intrinsics))
 570       warning("CRC32 Intrinsics requires CLMUL instructions (not available on this CPU)");
 571     FLAG_SET_DEFAULT(UseCRC32Intrinsics, false);
 572   }
 573 
 574   // The AES intrinsic stubs require AES instruction support (of course)
 575   // but also require sse3 mode for instructions it use.
 576   if (UseAES && (UseSSE > 2)) {
 577     if (FLAG_IS_DEFAULT(UseAESIntrinsics)) {
 578       UseAESIntrinsics = true;
 579     }
 580   } else if (UseAESIntrinsics) {
 581     if (!FLAG_IS_DEFAULT(UseAESIntrinsics))
 582       warning("AES intrinsics are not available on this CPU");
 583     FLAG_SET_DEFAULT(UseAESIntrinsics, false);
 584   }
 585 
 586   if (UseSHA) {
 587     warning("SHA instructions are not available on this CPU");
 588     FLAG_SET_DEFAULT(UseSHA, false);
 589   }
 590   if (UseSHA1Intrinsics || UseSHA256Intrinsics || UseSHA512Intrinsics) {
 591     warning("SHA intrinsics are not available on this CPU");
 592     FLAG_SET_DEFAULT(UseSHA1Intrinsics, false);
 593     FLAG_SET_DEFAULT(UseSHA256Intrinsics, false);
 594     FLAG_SET_DEFAULT(UseSHA512Intrinsics, false);
 595   }
 596 
 597   // Adjust RTM (Restricted Transactional Memory) flags
 598   if (!supports_rtm() && UseRTMLocking) {
 599     // Can't continue because UseRTMLocking affects UseBiasedLocking flag
 600     // setting during arguments processing. See use_biased_locking().
 601     // VM_Version_init() is executed after UseBiasedLocking is used
 602     // in Thread::allocate().
 603     vm_exit_during_initialization("RTM instructions are not available on this CPU");
 604   }
 605 
 606 #if INCLUDE_RTM_OPT
 607   if (UseRTMLocking) {
 608     if (is_intel_family_core()) {
 609       if ((_model == CPU_MODEL_HASWELL_E3) ||
 610           (_model == CPU_MODEL_HASWELL_E7 && _stepping < 3) ||
 611           (_model == CPU_MODEL_BROADWELL  && _stepping < 4)) {
 612         if (!UnlockExperimentalVMOptions) {
 613           vm_exit_during_initialization("UseRTMLocking is only available as experimental option on this platform. It must be enabled via -XX:+UnlockExperimentalVMOptions flag.");
 614         } else {
 615           warning("UseRTMLocking is only available as experimental option on this platform.");
 616         }
 617       }
 618     }
 619     if (!FLAG_IS_CMDLINE(UseRTMLocking)) {
 620       // RTM locking should be used only for applications with
 621       // high lock contention. For now we do not use it by default.
 622       vm_exit_during_initialization("UseRTMLocking flag should be only set on command line");
 623     }
 624     if (!is_power_of_2(RTMTotalCountIncrRate)) {
 625       warning("RTMTotalCountIncrRate must be a power of 2, resetting it to 64");
 626       FLAG_SET_DEFAULT(RTMTotalCountIncrRate, 64);
 627     }
 628     if (RTMAbortRatio < 0 || RTMAbortRatio > 100) {
 629       warning("RTMAbortRatio must be in the range 0 to 100, resetting it to 50");
 630       FLAG_SET_DEFAULT(RTMAbortRatio, 50);
 631     }
 632   } else { // !UseRTMLocking
 633     if (UseRTMForStackLocks) {
 634       if (!FLAG_IS_DEFAULT(UseRTMForStackLocks)) {
 635         warning("UseRTMForStackLocks flag should be off when UseRTMLocking flag is off");
 636       }
 637       FLAG_SET_DEFAULT(UseRTMForStackLocks, false);
 638     }
 639     if (UseRTMDeopt) {
 640       FLAG_SET_DEFAULT(UseRTMDeopt, false);
 641     }
 642     if (PrintPreciseRTMLockingStatistics) {
 643       FLAG_SET_DEFAULT(PrintPreciseRTMLockingStatistics, false);
 644     }
 645   }
 646 #else
 647   if (UseRTMLocking) {
 648     // Only C2 does RTM locking optimization.
 649     // Can't continue because UseRTMLocking affects UseBiasedLocking flag
 650     // setting during arguments processing. See use_biased_locking().
 651     vm_exit_during_initialization("RTM locking optimization is not supported in this VM");
 652   }
 653 #endif
 654 
 655 #ifdef COMPILER2
 656   if (UseFPUForSpilling) {
 657     if (UseSSE < 2) {
 658       // Only supported with SSE2+
 659       FLAG_SET_DEFAULT(UseFPUForSpilling, false);
 660     }
 661   }
 662   if (MaxVectorSize > 0) {
 663     if (!is_power_of_2(MaxVectorSize)) {
 664       warning("MaxVectorSize must be a power of 2");
 665       FLAG_SET_DEFAULT(MaxVectorSize, 32);
 666     }
 667     if (MaxVectorSize > 32) {
 668       FLAG_SET_DEFAULT(MaxVectorSize, 32);
 669     }
 670     if (MaxVectorSize > 16 && (UseAVX == 0 || !os_supports_avx_vectors())) {
 671       // 32 bytes vectors (in YMM) are only supported with AVX+
 672       FLAG_SET_DEFAULT(MaxVectorSize, 16);
 673     }
 674     if (UseSSE < 2) {
 675       // Vectors (in XMM) are only supported with SSE2+
 676       FLAG_SET_DEFAULT(MaxVectorSize, 0);
 677     }
 678 #ifdef ASSERT
 679     if (supports_avx() && PrintMiscellaneous && Verbose && TraceNewVectors) {
 680       tty->print_cr("State of YMM registers after signal handle:");
 681       int nreg = 2 LP64_ONLY(+2);
 682       const char* ymm_name[4] = {"0", "7", "8", "15"};
 683       for (int i = 0; i < nreg; i++) {
 684         tty->print("YMM%s:", ymm_name[i]);
 685         for (int j = 7; j >=0; j--) {
 686           tty->print(" %x", _cpuid_info.ymm_save[i*8 + j]);
 687         }
 688         tty->cr();
 689       }
 690     }
 691 #endif
 692   }
 693 
 694 #ifdef _LP64
 695   if (FLAG_IS_DEFAULT(UseMultiplyToLenIntrinsic)) {
 696     UseMultiplyToLenIntrinsic = true;
 697   }
 698 #else
 699   if (UseMultiplyToLenIntrinsic) {
 700     if (!FLAG_IS_DEFAULT(UseMultiplyToLenIntrinsic)) {
 701       warning("multiplyToLen intrinsic is not available in 32-bit VM");
 702     }
 703     FLAG_SET_DEFAULT(UseMultiplyToLenIntrinsic, false);
 704   }
 705 #endif
 706 #endif // COMPILER2
 707 
 708   // On new cpus instructions which update whole XMM register should be used
 709   // to prevent partial register stall due to dependencies on high half.
 710   //
 711   // UseXmmLoadAndClearUpper == true  --> movsd(xmm, mem)
 712   // UseXmmLoadAndClearUpper == false --> movlpd(xmm, mem)
 713   // UseXmmRegToRegMoveAll == true  --> movaps(xmm, xmm), movapd(xmm, xmm).
 714   // UseXmmRegToRegMoveAll == false --> movss(xmm, xmm),  movsd(xmm, xmm).
 715 
 716   if( is_amd() ) { // AMD cpus specific settings
 717     if( supports_sse2() && FLAG_IS_DEFAULT(UseAddressNop) ) {
 718       // Use it on new AMD cpus starting from Opteron.
 719       UseAddressNop = true;
 720     }
 721     if( supports_sse2() && FLAG_IS_DEFAULT(UseNewLongLShift) ) {
 722       // Use it on new AMD cpus starting from Opteron.
 723       UseNewLongLShift = true;
 724     }
 725     if( FLAG_IS_DEFAULT(UseXmmLoadAndClearUpper) ) {
 726       if( supports_sse4a() ) {
 727         UseXmmLoadAndClearUpper = true; // use movsd only on '10h' Opteron
 728       } else {
 729         UseXmmLoadAndClearUpper = false;
 730       }
 731     }
 732     if( FLAG_IS_DEFAULT(UseXmmRegToRegMoveAll) ) {
 733       if( supports_sse4a() ) {
 734         UseXmmRegToRegMoveAll = true; // use movaps, movapd only on '10h'
 735       } else {
 736         UseXmmRegToRegMoveAll = false;
 737       }
 738     }
 739     if( FLAG_IS_DEFAULT(UseXmmI2F) ) {
 740       if( supports_sse4a() ) {
 741         UseXmmI2F = true;
 742       } else {
 743         UseXmmI2F = false;
 744       }
 745     }
 746     if( FLAG_IS_DEFAULT(UseXmmI2D) ) {
 747       if( supports_sse4a() ) {
 748         UseXmmI2D = true;
 749       } else {
 750         UseXmmI2D = false;
 751       }
 752     }
 753     if( FLAG_IS_DEFAULT(UseSSE42Intrinsics) ) {
 754       if( supports_sse4_2() && UseSSE >= 4 ) {
 755         UseSSE42Intrinsics = true;
 756       }
 757     }
 758 
 759     // some defaults for AMD family 15h
 760     if ( cpu_family() == 0x15 ) {
 761       // On family 15h processors default is no sw prefetch
 762       if (FLAG_IS_DEFAULT(AllocatePrefetchStyle)) {
 763         AllocatePrefetchStyle = 0;
 764       }
 765       // Also, if some other prefetch style is specified, default instruction type is PREFETCHW
 766       if (FLAG_IS_DEFAULT(AllocatePrefetchInstr)) {
 767         AllocatePrefetchInstr = 3;
 768       }
 769       // On family 15h processors use XMM and UnalignedLoadStores for Array Copy
 770       if (supports_sse2() && FLAG_IS_DEFAULT(UseXMMForArrayCopy)) {
 771         UseXMMForArrayCopy = true;
 772       }
 773       if (supports_sse2() && FLAG_IS_DEFAULT(UseUnalignedLoadStores)) {
 774         UseUnalignedLoadStores = true;
 775       }
 776     }
 777 
 778 #ifdef COMPILER2
 779     if (MaxVectorSize > 16) {
 780       // Limit vectors size to 16 bytes on current AMD cpus.
 781       FLAG_SET_DEFAULT(MaxVectorSize, 16);
 782     }
 783 #endif // COMPILER2
 784   }
 785 
 786   if( is_intel() ) { // Intel cpus specific settings
 787     if( FLAG_IS_DEFAULT(UseStoreImmI16) ) {
 788       UseStoreImmI16 = false; // don't use it on Intel cpus
 789     }
 790     if( cpu_family() == 6 || cpu_family() == 15 ) {
 791       if( FLAG_IS_DEFAULT(UseAddressNop) ) {
 792         // Use it on all Intel cpus starting from PentiumPro
 793         UseAddressNop = true;
 794       }
 795     }
 796     if( FLAG_IS_DEFAULT(UseXmmLoadAndClearUpper) ) {
 797       UseXmmLoadAndClearUpper = true; // use movsd on all Intel cpus
 798     }
 799     if( FLAG_IS_DEFAULT(UseXmmRegToRegMoveAll) ) {
 800       if( supports_sse3() ) {
 801         UseXmmRegToRegMoveAll = true; // use movaps, movapd on new Intel cpus
 802       } else {
 803         UseXmmRegToRegMoveAll = false;
 804       }
 805     }
 806     if( cpu_family() == 6 && supports_sse3() ) { // New Intel cpus
 807 #ifdef COMPILER2
 808       if( FLAG_IS_DEFAULT(MaxLoopPad) ) {
 809         // For new Intel cpus do the next optimization:
 810         // don't align the beginning of a loop if there are enough instructions
 811         // left (NumberOfLoopInstrToAlign defined in c2_globals.hpp)
 812         // in current fetch line (OptoLoopAlignment) or the padding
 813         // is big (> MaxLoopPad).
 814         // Set MaxLoopPad to 11 for new Intel cpus to reduce number of
 815         // generated NOP instructions. 11 is the largest size of one
 816         // address NOP instruction '0F 1F' (see Assembler::nop(i)).
 817         MaxLoopPad = 11;
 818       }
 819 #endif // COMPILER2
 820       if (FLAG_IS_DEFAULT(UseXMMForArrayCopy)) {
 821         UseXMMForArrayCopy = true; // use SSE2 movq on new Intel cpus
 822       }
 823       if (supports_sse4_2() && supports_ht()) { // Newest Intel cpus
 824         if (FLAG_IS_DEFAULT(UseUnalignedLoadStores)) {
 825           UseUnalignedLoadStores = true; // use movdqu on newest Intel cpus
 826         }
 827       }
 828       if (supports_sse4_2() && UseSSE >= 4) {
 829         if (FLAG_IS_DEFAULT(UseSSE42Intrinsics)) {
 830           UseSSE42Intrinsics = true;
 831         }
 832       }
 833     }
 834     if ((cpu_family() == 0x06) &&
 835         ((extended_cpu_model() == 0x36) || // Centerton
 836          (extended_cpu_model() == 0x37) || // Silvermont
 837          (extended_cpu_model() == 0x4D))) {
 838 #ifdef COMPILER2
 839       if (FLAG_IS_DEFAULT(OptoScheduling)) {
 840         OptoScheduling = true;
 841       }
 842 #endif
 843       if (supports_sse4_2()) { // Silvermont
 844         if (FLAG_IS_DEFAULT(UseUnalignedLoadStores)) {
 845           UseUnalignedLoadStores = true; // use movdqu on newest Intel cpus
 846         }
 847       }
 848     }
 849     if(FLAG_IS_DEFAULT(AllocatePrefetchInstr) && supports_3dnow_prefetch()) {
 850       AllocatePrefetchInstr = 3;
 851     }
 852   }
 853 
 854   // Use count leading zeros count instruction if available.
 855   if (supports_lzcnt()) {
 856     if (FLAG_IS_DEFAULT(UseCountLeadingZerosInstruction)) {
 857       UseCountLeadingZerosInstruction = true;
 858     }
 859    } else if (UseCountLeadingZerosInstruction) {
 860     warning("lzcnt instruction is not available on this CPU");
 861     FLAG_SET_DEFAULT(UseCountLeadingZerosInstruction, false);
 862   }
 863 
 864   // Use count trailing zeros instruction if available
 865   if (supports_bmi1()) {
 866     // tzcnt does not require VEX prefix
 867     if (FLAG_IS_DEFAULT(UseCountTrailingZerosInstruction)) {
 868       UseCountTrailingZerosInstruction = true;
 869     }
 870   } else if (UseCountTrailingZerosInstruction) {
 871     warning("tzcnt instruction is not available on this CPU");
 872     FLAG_SET_DEFAULT(UseCountTrailingZerosInstruction, false);
 873   }
 874 
 875   // BMI instructions use an encoding with VEX prefix.
 876   // VEX prefix is generated only when AVX > 0.
 877   if (supports_bmi1() && supports_avx()) {
 878     if (FLAG_IS_DEFAULT(UseBMI1Instructions)) {
 879       UseBMI1Instructions = true;
 880     }
 881   } else if (UseBMI1Instructions) {
 882     warning("BMI1 instructions are not available on this CPU (AVX is also required)");
 883     FLAG_SET_DEFAULT(UseBMI1Instructions, false);
 884   }
 885 
 886   if (supports_bmi2() && supports_avx()) {
 887     if (FLAG_IS_DEFAULT(UseBMI2Instructions)) {
 888       UseBMI2Instructions = true;
 889     }
 890   } else if (UseBMI2Instructions) {
 891     warning("BMI2 instructions are not available on this CPU (AVX is also required)");
 892     FLAG_SET_DEFAULT(UseBMI2Instructions, false);
 893   }
 894 
 895   // Use population count instruction if available.
 896   if (supports_popcnt()) {
 897     if (FLAG_IS_DEFAULT(UsePopCountInstruction)) {
 898       UsePopCountInstruction = true;
 899     }
 900   } else if (UsePopCountInstruction) {
 901     warning("POPCNT instruction is not available on this CPU");
 902     FLAG_SET_DEFAULT(UsePopCountInstruction, false);
 903   }
 904 
 905   // Use fast-string operations if available.
 906   if (supports_erms()) {
 907     if (FLAG_IS_DEFAULT(UseFastStosb)) {
 908       UseFastStosb = true;
 909     }
 910   } else if (UseFastStosb) {
 911     warning("fast-string operations are not available on this CPU");
 912     FLAG_SET_DEFAULT(UseFastStosb, false);
 913   }
 914 
 915 #ifdef COMPILER2
 916   if (FLAG_IS_DEFAULT(AlignVector)) {
 917     // Modern processors allow misaligned memory operations for vectors.
 918     AlignVector = !UseUnalignedLoadStores;
 919   }
 920 #endif // COMPILER2
 921 
 922   assert(0 <= ReadPrefetchInstr && ReadPrefetchInstr <= 3, "invalid value");
 923   assert(0 <= AllocatePrefetchInstr && AllocatePrefetchInstr <= 3, "invalid value");
 924 
 925   // set valid Prefetch instruction
 926   if( ReadPrefetchInstr < 0 ) ReadPrefetchInstr = 0;
 927   if( ReadPrefetchInstr > 3 ) ReadPrefetchInstr = 3;
 928   if( ReadPrefetchInstr == 3 && !supports_3dnow_prefetch() ) ReadPrefetchInstr = 0;
 929   if( !supports_sse() && supports_3dnow_prefetch() ) ReadPrefetchInstr = 3;
 930 
 931   if( AllocatePrefetchInstr < 0 ) AllocatePrefetchInstr = 0;
 932   if( AllocatePrefetchInstr > 3 ) AllocatePrefetchInstr = 3;
 933   if( AllocatePrefetchInstr == 3 && !supports_3dnow_prefetch() ) AllocatePrefetchInstr=0;
 934   if( !supports_sse() && supports_3dnow_prefetch() ) AllocatePrefetchInstr = 3;
 935 
 936   // Allocation prefetch settings
 937   intx cache_line_size = prefetch_data_size();
 938   if( cache_line_size > AllocatePrefetchStepSize )
 939     AllocatePrefetchStepSize = cache_line_size;
 940 
 941   assert(AllocatePrefetchLines > 0, "invalid value");
 942   if( AllocatePrefetchLines < 1 )     // set valid value in product VM
 943     AllocatePrefetchLines = 3;
 944   assert(AllocateInstancePrefetchLines > 0, "invalid value");
 945   if( AllocateInstancePrefetchLines < 1 ) // set valid value in product VM
 946     AllocateInstancePrefetchLines = 1;
 947 
 948   AllocatePrefetchDistance = allocate_prefetch_distance();
 949   AllocatePrefetchStyle    = allocate_prefetch_style();
 950 
 951   if (is_intel() && cpu_family() == 6 && supports_sse3()) {
 952     if (AllocatePrefetchStyle == 2) { // watermark prefetching on Core
 953 #ifdef _LP64
 954       AllocatePrefetchDistance = 384;
 955 #else
 956       AllocatePrefetchDistance = 320;
 957 #endif
 958     }
 959     if (supports_sse4_2() && supports_ht()) { // Nehalem based cpus
 960       AllocatePrefetchDistance = 192;
 961       AllocatePrefetchLines = 4;
 962     }
 963 #ifdef COMPILER2
 964     if (supports_sse4_2()) {
 965       if (FLAG_IS_DEFAULT(UseFPUForSpilling)) {
 966         FLAG_SET_DEFAULT(UseFPUForSpilling, true);
 967       }
 968     }
 969 #endif
 970   }
 971   assert(AllocatePrefetchDistance % AllocatePrefetchStepSize == 0, "invalid value");
 972 
 973 #ifdef _LP64
 974   // Prefetch settings
 975   PrefetchCopyIntervalInBytes = prefetch_copy_interval_in_bytes();
 976   PrefetchScanIntervalInBytes = prefetch_scan_interval_in_bytes();
 977   PrefetchFieldsAhead         = prefetch_fields_ahead();
 978 #endif
 979 
 980   if (FLAG_IS_DEFAULT(ContendedPaddingWidth) &&
 981      (cache_line_size > ContendedPaddingWidth))
 982      ContendedPaddingWidth = cache_line_size;
 983 
 984 #ifndef PRODUCT
 985   if (PrintMiscellaneous && Verbose) {
 986     tty->print_cr("Logical CPUs per core: %u",
 987                   logical_processors_per_package());
 988     tty->print_cr("L1 data cache line size: %u", L1_data_cache_line_size());
 989     tty->print("UseSSE=%d", (int) UseSSE);
 990     if (UseAVX > 0) {
 991       tty->print("  UseAVX=%d", (int) UseAVX);
 992     }
 993     if (UseAES) {
 994       tty->print("  UseAES=1");
 995     }
 996 #ifdef COMPILER2
 997     if (MaxVectorSize > 0) {
 998       tty->print("  MaxVectorSize=%d", (int) MaxVectorSize);
 999     }
1000 #endif
1001     tty->cr();
1002     tty->print("Allocation");
1003     if (AllocatePrefetchStyle <= 0 || UseSSE == 0 && !supports_3dnow_prefetch()) {
1004       tty->print_cr(": no prefetching");
1005     } else {
1006       tty->print(" prefetching: ");
1007       if (UseSSE == 0 && supports_3dnow_prefetch()) {
1008         tty->print("PREFETCHW");
1009       } else if (UseSSE >= 1) {
1010         if (AllocatePrefetchInstr == 0) {
1011           tty->print("PREFETCHNTA");
1012         } else if (AllocatePrefetchInstr == 1) {
1013           tty->print("PREFETCHT0");
1014         } else if (AllocatePrefetchInstr == 2) {
1015           tty->print("PREFETCHT2");
1016         } else if (AllocatePrefetchInstr == 3) {
1017           tty->print("PREFETCHW");
1018         }
1019       }
1020       if (AllocatePrefetchLines > 1) {
1021         tty->print_cr(" at distance %d, %d lines of %d bytes", (int) AllocatePrefetchDistance, (int) AllocatePrefetchLines, (int) AllocatePrefetchStepSize);
1022       } else {
1023         tty->print_cr(" at distance %d, one line of %d bytes", (int) AllocatePrefetchDistance, (int) AllocatePrefetchStepSize);
1024       }
1025     }
1026 
1027     if (PrefetchCopyIntervalInBytes > 0) {
1028       tty->print_cr("PrefetchCopyIntervalInBytes %d", (int) PrefetchCopyIntervalInBytes);
1029     }
1030     if (PrefetchScanIntervalInBytes > 0) {
1031       tty->print_cr("PrefetchScanIntervalInBytes %d", (int) PrefetchScanIntervalInBytes);
1032     }
1033     if (PrefetchFieldsAhead > 0) {
1034       tty->print_cr("PrefetchFieldsAhead %d", (int) PrefetchFieldsAhead);
1035     }
1036     if (ContendedPaddingWidth > 0) {
1037       tty->print_cr("ContendedPaddingWidth %d", (int) ContendedPaddingWidth);
1038     }
1039   }
1040 #endif // !PRODUCT
1041 }
1042 
1043 bool VM_Version::use_biased_locking() {
1044 #if INCLUDE_RTM_OPT
1045   // RTM locking is most useful when there is high lock contention and
1046   // low data contention.  With high lock contention the lock is usually
1047   // inflated and biased locking is not suitable for that case.
1048   // RTM locking code requires that biased locking is off.
1049   // Note: we can't switch off UseBiasedLocking in get_processor_features()
1050   // because it is used by Thread::allocate() which is called before
1051   // VM_Version::initialize().
1052   if (UseRTMLocking && UseBiasedLocking) {
1053     if (FLAG_IS_DEFAULT(UseBiasedLocking)) {
1054       FLAG_SET_DEFAULT(UseBiasedLocking, false);
1055     } else {
1056       warning("Biased locking is not supported with RTM locking; ignoring UseBiasedLocking flag." );
1057       UseBiasedLocking = false;
1058     }
1059   }
1060 #endif
1061   return UseBiasedLocking;
1062 }
1063 
1064 void VM_Version::initialize() {
1065   ResourceMark rm;
1066   // Making this stub must be FIRST use of assembler
1067 
1068   stub_blob = BufferBlob::create("get_cpu_info_stub", stub_size);
1069   if (stub_blob == NULL) {
1070     vm_exit_during_initialization("Unable to allocate get_cpu_info_stub");
1071   }
1072   CodeBuffer c(stub_blob);
1073   VM_Version_StubGenerator g(&c);
1074   get_cpu_info_stub = CAST_TO_FN_PTR(get_cpu_info_stub_t,
1075                                      g.generate_get_cpu_info());
1076 
1077   get_processor_features();
1078 }