Constants.h 10.9 KB
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/* ----------------------------------------------------------------------------
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 *
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 * (c) The GHC Team, 1998-2009
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 *
 * Constants
 *
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 * NOTE: this information is used by both the compiler and the RTS.
 * Some of it is tweakable, and some of it must be kept up to date
 * with various other parts of the system.
 *
 * Constants which are derived automatically from other definitions in
 * the system (eg. structure sizes) are generated into the file
 * DerivedConstants.h by a C program (mkDerivedConstantsHdr).
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 *
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 * To understand the structure of the RTS headers, see the wiki:
 *   http://hackage.haskell.org/trac/ghc/wiki/Commentary/SourceTree/Includes
 *
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 * -------------------------------------------------------------------------- */

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#ifndef RTS_CONSTANTS_H
#define RTS_CONSTANTS_H
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/* -----------------------------------------------------------------------------
   Minimum closure sizes

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   This is the minimum number of words in the payload of a
   heap-allocated closure, so that the closure has enough room to be
   overwritten with a forwarding pointer during garbage collection.
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   -------------------------------------------------------------------------- */

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#define MIN_PAYLOAD_SIZE 1
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/* -----------------------------------------------------------------------------
   Constants to do with specialised closure types.
   -------------------------------------------------------------------------- */

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/* We have some pre-compiled selector thunks defined in rts/StgStdThunks.hc.
 * This constant defines the highest selectee index that we can replace with a 
 * reference to the pre-compiled code.
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 */

#define MAX_SPEC_SELECTEE_SIZE 15

/* Vector-apply thunks.  These thunks just push their free variables
 * on the stack and enter the first one.  They're a bit like PAPs, but
 * don't have a dynamic size.  We've pre-compiled a few to save
 * space. 
 */

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#define MAX_SPEC_AP_SIZE       7
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/* Specialised FUN/THUNK/CONSTR closure types */

#define MAX_SPEC_THUNK_SIZE    2
#define MAX_SPEC_FUN_SIZE      2
#define MAX_SPEC_CONSTR_SIZE   2

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/* Range of built-in table of static small int-like and char-like closures. 
 * 
 *   NB. This corresponds with the number of actual INTLIKE/CHARLIKE
 *   closures defined in rts/StgMiscClosures.cmm.
 */
#define MAX_INTLIKE 		16
#define MIN_INTLIKE 		(-16)

#define MAX_CHARLIKE		255
#define MIN_CHARLIKE		0

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/* Each byte in the card table for an StgMutaArrPtrs covers
 * (1<<MUT_ARR_PTRS_CARD_BITS) elements in the array.  To find a good
 * value for this, I used the benchmarks nofib/gc/hash,
 * nofib/gc/graph, and nofib/gc/gc_bench.
 */
#define MUT_ARR_PTRS_CARD_BITS 7

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/* -----------------------------------------------------------------------------
   STG Registers.

   Note that in MachRegs.h we define how many of these registers are
   *real* machine registers, and not just offsets in the Register Table.
   -------------------------------------------------------------------------- */

#define MAX_VANILLA_REG 8
#define MAX_FLOAT_REG   4
#define MAX_DOUBLE_REG  2
#define MAX_LONG_REG    1

/* -----------------------------------------------------------------------------
   Semi-Tagging constants

   Old Comments about this stuff:

   Tags for indirection nodes and ``other'' (probably unevaluated) nodes;
   normal-form values of algebraic data types will have tags 0, 1, ...
   
   @INFO_IND_TAG@ is different from @INFO_OTHER_TAG@ just so we can count
   how often we bang into indirection nodes; that's all.  (WDP 95/11)

   ToDo: find out if we need any of this.
   -------------------------------------------------------------------------- */

#define INFO_OTHER_TAG		(-1)
#define INFO_IND_TAG		(-2)
#define INFO_FIRST_TAG		0

/* -----------------------------------------------------------------------------
   How much C stack to reserve for local temporaries when in the STG
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   world.  Used in StgCRun.c.
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   -------------------------------------------------------------------------- */

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#define RESERVED_C_STACK_BYTES (2048 * SIZEOF_LONG)
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/* -----------------------------------------------------------------------------
   How much Haskell stack space to reserve for the saving of registers
   etc. in the case of a stack/heap overflow.
   
   This must be large enough to accomodate the largest stack frame
   pushed in one of the heap check fragments in HeapStackCheck.hc
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   (ie. currently the generic heap checks - 3 words for StgRetDyn,
   18 words for the saved registers, see StgMacros.h).  

   In the event of an unboxed tuple or let-no-escape stack/heap check
   failure, there will be other words on the stack which are covered
   by the RET_DYN frame.  These will have been accounted for by stack
   checks however, so we don't need to allow for them here.
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   -------------------------------------------------------------------------- */

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#define RESERVED_STACK_WORDS 21
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/* -----------------------------------------------------------------------------
   The limit on the size of the stack check performed when we enter an
   AP_STACK, in words.  See raiseAsync() and bug #1466.
   -------------------------------------------------------------------------- */

#define AP_STACK_SPLIM 1024

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/* -----------------------------------------------------------------------------
   Storage manager constants
   -------------------------------------------------------------------------- */

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/* The size of a block (2^BLOCK_SHIFT bytes) */
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#define BLOCK_SHIFT  12
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/* The size of a megablock (2^MBLOCK_SHIFT bytes) */
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#define MBLOCK_SHIFT   20

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/* -----------------------------------------------------------------------------
   Bitmap/size fields (used in info tables)
   -------------------------------------------------------------------------- */
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/* In a 32-bit bitmap field, we use 5 bits for the size, and 27 bits
 * for the bitmap.  If the bitmap requires more than 27 bits, then we
 * store it in a separate array, and leave a pointer in the bitmap
 * field.  On a 64-bit machine, the sizes are extended accordingly.
 */
#if SIZEOF_VOID_P == 4
#define BITMAP_SIZE_MASK     0x1f
#define BITMAP_BITS_SHIFT    5
#elif SIZEOF_VOID_P == 8
#define BITMAP_SIZE_MASK     0x3f
#define BITMAP_BITS_SHIFT    6
#else
#error unknown SIZEOF_VOID_P
#endif

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/* -----------------------------------------------------------------------------
   Lag/Drag/Void constants
   -------------------------------------------------------------------------- */

/*
  An LDV word is divided into 3 parts: state bits (LDV_STATE_MASK), creation 
  time bits (LDV_CREATE_MASK), and last use time bits (LDV_LAST_MASK). 
 */
#if SIZEOF_VOID_P == 8
#define LDV_SHIFT               30
#define LDV_STATE_MASK          0x1000000000000000
#define LDV_CREATE_MASK         0x0FFFFFFFC0000000
#define LDV_LAST_MASK           0x000000003FFFFFFF
#define LDV_STATE_CREATE        0x0000000000000000
#define LDV_STATE_USE           0x1000000000000000
#else
#define LDV_SHIFT               15
#define LDV_STATE_MASK          0x40000000 
#define LDV_CREATE_MASK         0x3FFF8000
#define LDV_LAST_MASK           0x00007FFF
#define LDV_STATE_CREATE        0x00000000
#define LDV_STATE_USE           0x40000000
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#endif /* SIZEOF_VOID_P */
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/* -----------------------------------------------------------------------------
   TSO related constants
   -------------------------------------------------------------------------- */

/*
 * Constants for the what_next field of a TSO, which indicates how it
 * is to be run.
 */
#define ThreadRunGHC    1	/* return to address on top of stack */
#define ThreadInterpret 2	/* interpret this thread */
#define ThreadKilled	3	/* thread has died, don't run it */
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#define ThreadComplete  4       /* thread has finished */
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/*
 * Constants for the why_blocked field of a TSO
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 * NB. keep these in sync with GHC/Conc.lhs: threadStatus
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 */
#define NotBlocked          0
#define BlockedOnMVar       1
#define BlockedOnBlackHole  2
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#define BlockedOnRead       3
#define BlockedOnWrite      4
#define BlockedOnDelay      5
#define BlockedOnSTM        6
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/* Win32 only: */
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#define BlockedOnDoProc     7
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/* Only relevant for PAR: */
  /* blocked on a remote closure represented by a Global Address: */
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#define BlockedOnGA         8
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  /* same as above but without sending a Fetch message */
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#define BlockedOnGA_NoSend  9
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/* Only relevant for THREADED_RTS: */
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#define BlockedOnCCall      10
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#define BlockedOnCCall_Interruptible 11
   /* same as above but permit killing the worker thread */
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/* Involved in a message sent to tso->msg_cap */
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#define BlockedOnMsgThrowTo 12

/* The thread is not on any run queues, but can be woken up 
   by tryWakeupThread() */
#define ThreadMigrating     13

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/*
 * These constants are returned to the scheduler by a thread that has
 * stopped for one reason or another.  See typedef StgThreadReturnCode
 * in TSO.h.
 */
#define HeapOverflow   1		/* might also be StackOverflow */
#define StackOverflow  2
#define ThreadYielding 3
#define ThreadBlocked  4
#define ThreadFinished 5

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/* 
 * Flags for the tso->flags field.
 */

/*
 * TSO_LOCKED is set when a TSO is locked to a particular Capability.
 */
#define TSO_LOCKED  2

/*
 * TSO_BLOCKEX: the TSO is blocking exceptions
 *
 * TSO_INTERRUPTIBLE: the TSO can be interrupted if it blocks
 * interruptibly (eg. with BlockedOnMVar).
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 *
 * TSO_STOPPED_ON_BREAKPOINT: the thread is currently stopped in a breakpoint
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 */
#define TSO_BLOCKEX       4
#define TSO_INTERRUPTIBLE 8
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#define TSO_STOPPED_ON_BREAKPOINT 16 
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/*
 * Used by the sanity checker to check whether TSOs are on the correct
 * mutable list.
 */
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#define TSO_MARKED 64

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/*
 * Used to communicate between stackSqueeze() and
 * threadStackOverflow() that a thread's stack was squeezed and the
 * stack may not need to be expanded.
 */
#define TSO_SQUEEZED 128

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/* -----------------------------------------------------------------------------
   RET_DYN stack frames
   -------------------------------------------------------------------------- */

/* VERY MAGIC CONSTANTS! 
 * must agree with code in HeapStackCheck.c, stg_gen_chk, and
 * RESERVED_STACK_WORDS in Constants.h.
 */
#define RET_DYN_BITMAP_SIZE 8
#define RET_DYN_NONPTR_REGS_SIZE 10

/* Sanity check that RESERVED_STACK_WORDS is reasonable.  We can't
 * just derive RESERVED_STACK_WORDS because it's used in Haskell code
 * too.
 */
#if RESERVED_STACK_WORDS != (3 + RET_DYN_BITMAP_SIZE + RET_DYN_NONPTR_REGS_SIZE)
#error RESERVED_STACK_WORDS may be wrong!
#endif

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/*
 * The number of times we spin in a spin lock before yielding (see
 * #3758).  To tune this value, use the benchmark in #3758: run the
 * server with -N2 and the client both on a dual-core.  Also make sure
 * that the chosen value doesn't slow down any of the parallel
 * benchmarks in nofib/parallel.
 */
#define SPIN_COUNT 1000

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/* -----------------------------------------------------------------------------
   Spare workers per Capability in the threaded RTS

   No more than MAX_SPARE_WORKERS will be kept in the thread pool
   associated with each Capability.
   -------------------------------------------------------------------------- */

#define MAX_SPARE_WORKERS 6

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#endif /* RTS_CONSTANTS_H */