cpu/static_inst.hh

   1 /*
   2  * Copyright (c) 2003-2004 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef __STATIC_INST_HH__
  30 #define __STATIC_INST_HH__
  31
  32 #include <bitset>
  33 #include <string>
  34
  35 #include "sim/host.hh"
  36 #include "base/hashmap.hh"
  37 #include "base/refcnt.hh"
  38
  39 #include "cpu/full_cpu/op_class.hh"
  40 #include "targetarch/isa_traits.hh"
  41
  42 // forward declarations
  43 class ExecContext;
  44 class AlphaDynInst;
  45 class DynInst;
  46 class FastCPU;
  47 class SimpleCPU;
  48 class SymbolTable;
  49
  50 namespace Trace {
  51     class InstRecord;
  52 }
  53
  54 /**
  55  * Base, ISA-independent static instruction class.
  56  *
  57  * The main component of this class is the vector of flags and the
  58  * associated methods for reading them.  Any object that can rely
  59  * solely on these flags can process instructions without being
  60  * recompiled for multiple ISAs.
  61  */
  62 class StaticInstBase : public RefCounted
  63 {
  64   protected:
  65
  66     /// Set of boolean static instruction properties.
  67     ///
  68     /// Notes:
  69     /// - The IsInteger and IsFloating flags are based on the class of
  70     /// registers accessed by the instruction.  Although most
  71     /// instructions will have exactly one of these two flags set, it
  72     /// is possible for an instruction to have neither (e.g., direct
  73     /// unconditional branches, memory barriers) or both (e.g., an
  74     /// FP/int conversion).
  75     /// - If IsMemRef is set, then exactly one of IsLoad or IsStore
  76     /// will be set.
  77     /// - If IsControl is set, then exactly one of IsDirectControl or
  78     /// IsIndirect Control will be set, and exactly one of
  79     /// IsCondControl or IsUncondControl will be set.
  80     /// - IsSerializing, IsMemBarrier, and IsWriteBarrier are
  81     /// implemented as flags since in the current model there's no
  82     /// other way for instructions to inject behavior into the
  83     /// pipeline outside of fetch.  Once we go to an exec-in-exec CPU
  84     /// model we should be able to get rid of these flags and
  85     /// implement this behavior via the execute() methods.
  86     ///
  87     enum Flags {
  88         IsNop,          ///< Is a no-op (no effect at all).
  89
  90         IsInteger,      ///< References integer regs.
  91         IsFloating,     ///< References FP regs.
  92
  93         IsMemRef,       ///< References memory (load, store, or prefetch).
  94         IsLoad,         ///< Reads from memory (load or prefetch).
  95         IsStore,        ///< Writes to memory.
  96         IsInstPrefetch, ///< Instruction-cache prefetch.
  97         IsDataPrefetch, ///< Data-cache prefetch.
  98         IsCopy,         ///< Fast Cache block copy
  99
 100         IsControl,              ///< Control transfer instruction.
 101         IsDirectControl,        ///< PC relative control transfer.
 102         IsIndirectControl,      ///< Register indirect control transfer.
 103         IsCondControl,          ///< Conditional control transfer.
 104         IsUncondControl,        ///< Unconditional control transfer.
 105         IsCall,                 ///< Subroutine call.
 106         IsReturn,               ///< Subroutine return.
 107
 108         IsThreadSync,   ///< Thread synchronization operation.
 109
 110         IsSerializing,  ///< Serializes pipeline: won't execute until all
 111                         /// older instructions have committed.
 112         IsMemBarrier,   ///< Is a memory barrier
 113         IsWriteBarrier, ///< Is a write barrier
 114
 115         IsNonSpeculative, ///< Should not be executed speculatively
 116
 117         NumFlags
 118     };
 119
 120     /// Flag values for this instruction.
 121     std::bitset<NumFlags> flags;
 122
 123     /// See opClass().
 124     OpClass _opClass;
 125
 126     /// See numSrcRegs().
 127     int8_t _numSrcRegs;
 128
 129     /// See numDestRegs().
 130     int8_t _numDestRegs;
 131
 132     /// The following are used to track physical register usage
 133     /// for machines with separate int & FP reg files.
 134     //@{
 135     int8_t _numFPDestRegs;
 136     int8_t _numIntDestRegs;
 137     //@}
 138
 139     /// Constructor.
 140     /// It's important to initialize everything here to a sane
 141     /// default, since the decoder generally only overrides
 142     /// the fields that are meaningful for the particular
 143     /// instruction.
 144     StaticInstBase(OpClass __opClass)
 145         : _opClass(__opClass), _numSrcRegs(0), _numDestRegs(0),
 146           _numFPDestRegs(0), _numIntDestRegs(0)
 147     {
 148     }
 149
 150   public:
 151
 152     /// @name Register information.
 153     /// The sum of numFPDestRegs() and numIntDestRegs() equals
 154     /// numDestRegs().  The former two functions are used to track
 155     /// physical register usage for machines with separate int & FP
 156     /// reg files.
 157     //@{
 158     /// Number of source registers.
 159     int8_t numSrcRegs()  const { return _numSrcRegs; }
 160     /// Number of destination registers.
 161     int8_t numDestRegs() const { return _numDestRegs; }
 162     /// Number of floating-point destination regs.
 163     int8_t numFPDestRegs()  const { return _numFPDestRegs; }
 164     /// Number of integer destination regs.
 165     int8_t numIntDestRegs() const { return _numIntDestRegs; }
 166     //@}
 167
 168     /// @name Flag accessors.
 169     /// These functions are used to access the values of the various
 170     /// instruction property flags.  See StaticInstBase::Flags for descriptions
 171     /// of the individual flags.
 172     //@{
 173
 174     bool isNop()          const { return flags[IsNop]; }
 175
 176     bool isMemRef()       const { return flags[IsMemRef]; }
 177     bool isLoad()         const { return flags[IsLoad]; }
 178     bool isStore()        const { return flags[IsStore]; }
 179     bool isInstPrefetch() const { return flags[IsInstPrefetch]; }
 180     bool isDataPrefetch() const { return flags[IsDataPrefetch]; }
 181     bool isCopy()         const { return flags[IsCopy];}
 182
 183     bool isInteger()      const { return flags[IsInteger]; }
 184     bool isFloating()     const { return flags[IsFloating]; }
 185
 186     bool isControl()      const { return flags[IsControl]; }
 187     bool isCall()         const { return flags[IsCall]; }
 188     bool isReturn()       const { return flags[IsReturn]; }
 189     bool isDirectCtrl()   const { return flags[IsDirectControl]; }
 190     bool isIndirectCtrl() const { return flags[IsIndirectControl]; }
 191     bool isCondCtrl()     const { return flags[IsCondControl]; }
 192     bool isUncondCtrl()   const { return flags[IsUncondControl]; }
 193
 194     bool isThreadSync()   const { return flags[IsThreadSync]; }
 195     bool isSerializing()  const { return flags[IsSerializing]; }
 196     bool isMemBarrier()   const { return flags[IsMemBarrier]; }
 197     bool isWriteBarrier() const { return flags[IsWriteBarrier]; }
 198     bool isNonSpeculative() const { return flags[IsNonSpeculative]; }
 199     //@}
 200
 201     /// Operation class.  Used to select appropriate function unit in issue.
 202     OpClass opClass()     const { return _opClass; }
 203 };
 204
 205
 206 // forward declaration
 207 template <class ISA>
 208 class StaticInstPtr;
 209
 210 /**
 211  * Generic yet ISA-dependent static instruction class.
 212  *
 213  * This class builds on StaticInstBase, defining fields and interfaces
 214  * that are generic across all ISAs but that differ in details
 215  * according to the specific ISA being used.
 216  */
 217 template <class ISA>
 218 class StaticInst : public StaticInstBase
 219 {
 220   public:
 221
 222     /// Binary machine instruction type.
 223     typedef typename ISA::MachInst MachInst;
 224     /// Memory address type.
 225     typedef typename ISA::Addr     Addr;
 226     /// Logical register index type.
 227     typedef typename ISA::RegIndex RegIndex;
 228
 229     enum {
 230         MaxInstSrcRegs = ISA::MaxInstSrcRegs,   //< Max source regs
 231         MaxInstDestRegs = ISA::MaxInstDestRegs, //< Max dest regs
 232     };
 233
 234
 235     /// Return logical index (architectural reg num) of i'th destination reg.
 236     /// Only the entries from 0 through numDestRegs()-1 are valid.
 237     RegIndex destRegIdx(int i) const { return _destRegIdx[i]; }
 238
 239     /// Return logical index (architectural reg num) of i'th source reg.
 240     /// Only the entries from 0 through numSrcRegs()-1 are valid.
 241     RegIndex srcRegIdx(int i)  const { return _srcRegIdx[i]; }
 242
 243     /// Pointer to a statically allocated "null" instruction object.
 244     /// Used to give eaCompInst() and memAccInst() something to return
 245     /// when called on non-memory instructions.
 246     static StaticInstPtr<ISA> nullStaticInstPtr;
 247
 248     /**
 249      * Memory references only: returns "fake" instruction representing
 250      * the effective address part of the memory operation.  Used to
 251      * obtain the dependence info (numSrcRegs and srcRegIdx[]) for
 252      * just the EA computation.
 253      */
 254     virtual const
 255     StaticInstPtr<ISA> &eaCompInst() const { return nullStaticInstPtr; }
 256
 257     /**
 258      * Memory references only: returns "fake" instruction representing
 259      * the memory access part of the memory operation.  Used to
 260      * obtain the dependence info (numSrcRegs and srcRegIdx[]) for
 261      * just the memory access (not the EA computation).
 262      */
 263     virtual const
 264     StaticInstPtr<ISA> &memAccInst() const { return nullStaticInstPtr; }
 265
 266     /// The binary machine instruction.
 267     const MachInst machInst;
 268
 269   protected:
 270
 271     /// See destRegIdx().
 272     RegIndex _destRegIdx[MaxInstDestRegs];
 273     /// See srcRegIdx().
 274     RegIndex _srcRegIdx[MaxInstSrcRegs];
 275
 276     /**
 277      * Base mnemonic (e.g., "add").  Used by generateDisassembly()
 278      * methods.  Also useful to readily identify instructions from
 279      * within the debugger when #cachedDisassembly has not been
 280      * initialized.
 281      */
 282     const char *mnemonic;
 283
 284     /**
 285      * String representation of disassembly (lazily evaluated via
 286      * disassemble()).
 287      */
 288     std::string *cachedDisassembly;
 289
 290     /**
 291      * Internal function to generate disassembly string.
 292      */
 293     virtual std::string generateDisassembly(Addr pc,
 294                                             const SymbolTable *symtab) = 0;
 295
 296     /// Constructor.
 297     StaticInst(const char *_mnemonic, MachInst _machInst, OpClass __opClass)
 298         : StaticInstBase(__opClass),
 299           machInst(_machInst), mnemonic(_mnemonic), cachedDisassembly(0)
 300     {
 301     }
 302
 303   public:
 304
 305     virtual ~StaticInst()
 306     {
 307         if (cachedDisassembly)
 308             delete cachedDisassembly;
 309     }
 310
 311 #include "static_inst_impl.hh"
 312
 313     /**
 314      * Return the target address for a PC-relative branch.
 315      * Invalid if not a PC-relative branch (i.e. isDirectCtrl()
 316      * should be true).
 317      */
 318     virtual Addr branchTarget(Addr branchPC) const
 319     {
 320         panic("StaticInst::branchTarget() called on instruction "
 321               "that is not a PC-relative branch.");
 322     }
 323
 324     /**
 325      * Return the target address for an indirect branch (jump).  The
 326      * register value is read from the supplied execution context, so
 327      * the result is valid only if the execution context is about to
 328      * execute the branch in question.  Invalid if not an indirect
 329      * branch (i.e. isIndirectCtrl() should be true).
 330      */
 331     virtual Addr branchTarget(ExecContext *xc) const
 332     {
 333         panic("StaticInst::branchTarget() called on instruction "
 334               "that is not an indirect branch.");
 335     }
 336
 337     /**
 338      * Return true if the instruction is a control transfer, and if so,
 339      * return the target address as well.
 340      */
 341     bool hasBranchTarget(Addr pc, ExecContext *xc, Addr &tgt);
 342
 343     /**
 344      * Return string representation of disassembled instruction.
 345      * The default version of this function will call the internal
 346      * virtual generateDisassembly() function to get the string,
 347      * then cache it in #cachedDisassembly.  If the disassembly
 348      * should not be cached, this function should be overridden directly.
 349      */
 350     virtual const std::string &disassemble(Addr pc,
 351                                            const SymbolTable *symtab = 0)
 352     {
 353         if (!cachedDisassembly)
 354             cachedDisassembly =
 355                 new std::string(generateDisassembly(pc, symtab));
 356
 357         return *cachedDisassembly;
 358     }
 359
 360     /// Decoded instruction cache type.
 361     /// For now we're using a generic hash_map; this seems to work
 362     /// pretty well.
 363     typedef m5::hash_map<MachInst, StaticInstPtr<ISA> > DecodeCache;
 364
 365     /// A cache of decoded instruction objects.
 366     static DecodeCache decodeCache;
 367
 368     /**
 369      * Dump some basic stats on the decode cache hash map.
 370      * Only gets called if DECODE_CACHE_HASH_STATS is defined.
 371      */
 372     static void dumpDecodeCacheStats();
 373
 374     /// Decode a machine instruction.
 375     /// @param mach_inst The binary instruction to decode.
 376     /// @retval A pointer to the corresponding StaticInst object.
 377     static
 378     StaticInstPtr<ISA> decode(MachInst mach_inst)
 379     {
 380 #ifdef DECODE_CACHE_HASH_STATS
 381         // Simple stats on decode hash_map.  Turns out the default
 382         // hash function is as good as anything I could come up with.
 383         const int dump_every_n = 10000000;
 384         static int decodes_til_dump = dump_every_n;
 385
 386         if (--decodes_til_dump == 0) {
 387             dumpDecodeCacheStats();
 388             decodes_til_dump = dump_every_n;
 389         }
 390 #endif
 391
 392         typename DecodeCache::iterator iter = decodeCache.find(mach_inst);
 393         if (iter != decodeCache.end()) {
 394             return iter->second;
 395         }
 396
 397         StaticInstPtr<ISA> si = ISA::decodeInst(mach_inst);
 398         decodeCache[mach_inst] = si;
 399         return si;
 400     }
 401 };
 402
 403 typedef RefCountingPtr<StaticInstBase> StaticInstBasePtr;
 404
 405 /// Reference-counted pointer to a StaticInst object.
 406 /// This type should be used instead of "StaticInst<ISA> *" so that
 407 /// StaticInst objects can be properly reference-counted.
 408 template <class ISA>
 409 class StaticInstPtr : public RefCountingPtr<StaticInst<ISA> >
 410 {
 411   public:
 412     /// Constructor.
 413     StaticInstPtr()
 414         : RefCountingPtr<StaticInst<ISA> >()
 415     {
 416     }
 417
 418     /// Conversion from "StaticInst<ISA> *".
 419     StaticInstPtr(StaticInst<ISA> *p)
 420         : RefCountingPtr<StaticInst<ISA> >(p)
 421     {
 422     }
 423
 424     /// Copy constructor.
 425     StaticInstPtr(const StaticInstPtr &r)
 426         : RefCountingPtr<StaticInst<ISA> >(r)
 427     {
 428     }
 429
 430     /// Construct directly from machine instruction.
 431     /// Calls StaticInst<ISA>::decode().
 432     StaticInstPtr(typename ISA::MachInst mach_inst)
 433         : RefCountingPtr<StaticInst<ISA> >(StaticInst<ISA>::decode(mach_inst))
 434     {
 435     }
 436
 437     /// Convert to pointer to StaticInstBase class.
 438     operator const StaticInstBasePtr()
 439     {
 440         return get();
 441     }
 442 };
 443
 444 #endif // __STATIC_INST_HH__