include/host_regs.h

/*---------------------------------------------------------------*/
/*---                                                         ---*/
/*--- This file (host_regs.h) is                              ---*/
/*--- Copyright (c) 2004 OpenWorks LLP.  All rights reserved. ---*/
/*---                                                         ---*/
/*---------------------------------------------------------------*/

#ifndef __HOST_REGS_H
#define __HOST_REGS_H


/*---------------------------------------------------------*/
/*--- Representing HOST REGISTERS                       ---*/
/*---------------------------------------------------------*/

/* Host registers.  Stuff to represent:

   - The register number
   - The register class
   - Whether or not the register is a virtual reg.

   Registers are a 32-bit Int, thusly:

     bits 31-28  are the register class.
     bits 27-23  are 0000b for real register, 0001b for virtual register
     bits 23-0   register number

   Note (importantly) that by arranging that the class field is never
   0000b, any valid register looks like an extremely large int -- at
   least 2^28 -- and so there is little chance of confusing it with an
   integer array index in the register allocator.

   Note further that since the class field is never 1111b, no valid
   register can have the value INVALID_HREG.

   There are currently 3 register classes:

     int
     floating
     vector 
*/

typedef UInt HReg;

/* When extending this, do not use any value > 14 or < 0. */
typedef
enum { HRcInt=4,       /* 32-bit int */
       HRcInt64=5,     /* 64-bit int */
       HRcFloat=6,     /* 64-bit float */
       HRcVector=7,    /* 64-bit SIMD */
       HRcVector128=8  /* 128-bit SIMD */
   }
   HRegClass;

extern void ppHRegClass ( FILE*, HRegClass );


/* Print an HReg in a generic (non-target-specific) way. */
extern void ppHReg ( FILE*, HReg );

/* Construct/destruct. */
extern HReg mkHReg ( UInt regno, HRegClass rc, Bool virtual );

extern HRegClass hregClass     ( HReg );
extern Bool      hregIsVirtual ( HReg );
extern UInt      hregNumber    ( HReg );


#define INVALID_HREG ((HReg)0xFFFFFFFF)


/*---------------------------------------------------------*/
/*--- Recording register usage (for reg-alloc)          ---*/
/*---------------------------------------------------------*/

typedef
   enum { HRmRead, HRmWrite, HRmModify }
   HRegMode;


/* A struct for recording the usage of registers in instructions.
   This can get quite large, but we don't expect to allocate them
   dynamically, so there's no problem. 
*/
#define N_HREG_USAGE 4

typedef
   struct {
      HReg     hreg[N_HREG_USAGE];
      HRegMode mode[N_HREG_USAGE];
      Int      n_used;
   }
   HRegUsage;

extern void ppHRegUsage ( FILE*, HRegUsage* );

extern void initHRegUsage ( HRegUsage* );

/* Add a register to a usage table.  Combine incoming read uses with
   existing write uses into a modify use, and vice versa.  Do not
   create duplicate entries -- each reg should only be mentioned once.  
*/
extern void addHRegUse ( HRegUsage*, HRegMode, HReg );



/*---------------------------------------------------------*/
/*--- Indicating register remappings (for reg-alloc)    ---*/
/*---------------------------------------------------------*/

/* Note that such maps can only map virtual regs to real regs.
   addToHRegRenap will barf if given a pair not of that form.  As a
   result, no valid HRegRemap will bind a real reg to anything, and so
   if lookupHRegMap is given a real reg, it returns it unchanged.
   This is precisely the behaviour that the register allocator needs
   to impose its decisions on the instructions it processes.  */

#define N_HREG_REMAP 4

typedef
   struct {
      HReg orig       [N_HREG_REMAP];
      HReg replacement[N_HREG_REMAP];
      Int  n_used;
   }
   HRegRemap;

extern void ppHRegRemap     ( FILE*, HRegRemap* );
extern void initHRegRemap   ( HRegRemap* );
extern void addToHRegRemap  ( HRegRemap*, HReg, HReg );
extern HReg lookupHRegRemap ( HRegRemap*, HReg );


/*---------------------------------------------------------*/
/*--- Abstract instructions                             ---*/
/*---------------------------------------------------------*/

/* A type is needed to refer to pointers to instructions of any
   target.  Defining it like this means that HInstr* can stand in for
   X86Instr*, ArmInstr*, etc. */

typedef  void  HInstr;


/* An expandable array of HInstr*'s.  Handy for insn 
   selection and register allocation. */

typedef
   struct {
      HInstr** arr;
      Int      arr_size;
      Int      arr_used;
   }
   HInstrArray;

extern HInstrArray* newHInstrArray ( void );
extern void         deleteHInstrArray ( HInstrArray* );
extern void         addHInstr ( HInstrArray*, HInstr* );


#endif /* ndef __HOST_REGS_H */


/*---------------------------------------------------------*/
/*--- Reg alloc: TODO: move somewhere else              ---*/
/*---------------------------------------------------------*/

extern
HInstrArray* doRegisterAllocation (

   /* Incoming virtual-registerised code. */ 
   HInstrArray* instrs_in,
   Int          n_vregs,

   /* An array listing all the real registers the allocator may use,
      in no particular order. */
   HReg* available_real_regs,
   Int   n_available_real_regs,

   /* Return True iff the given insn is a reg-reg move, in which
      case also return the src and dst regs. */
   Bool (*isMove) (HInstr*, HReg*, HReg*),

   /* Get info about register usage in this insn. */
   void (*getRegUsage) (HRegUsage*, HInstr*),

   /* Apply a reg-reg mapping to an insn. */
   void (*mapRegs) (HRegRemap*, HInstr*),

   /* Return an insn to spill/restore a real reg to a spill slot
      offset. */
   HInstr* (*genSpill) ( HReg, Int ),
   HInstr* (*genReload) ( HReg, Int )
);



/*---------------------------------------------------------------*/
/*---                                             host_regs.h ---*/
/*---------------------------------------------------------------*/