Annotation of gforth/arch/alpha/machine.h, revision 1.3

1.1       anton       1: /* preliminary machine file for DEC Alpha
                      2: 
1.3     ! anton       3:   Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.
1.1       anton       4: 
                      5:   This file is part of Gforth.
                      6: 
                      7:   Gforth is free software; you can redistribute it and/or
                      8:   modify it under the terms of the GNU General Public License
                      9:   as published by the Free Software Foundation; either version 2
                     10:   of the License, or (at your option) any later version.
                     11: 
                     12:   This program is distributed in the hope that it will be useful,
                     13:   but WITHOUT ANY WARRANTY; without even the implied warranty of
                     14:   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
                     15:   GNU General Public License for more details.
                     16: 
                     17:   You should have received a copy of the GNU General Public License
                     18:   along with this program; if not, write to the Free Software
                     19:   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
                     20: */
                     21: 
                     22: /* Be careful: long long on Alpha are 64 bit :-(( */
                     23: #define LONG_LATENCY
                     24: 
                     25: #if !defined(USE_TOS) && !defined(USE_NO_TOS)
                     26: #define USE_TOS
                     27: #endif
                     28: 
                     29: #ifndef INDIRECT_THREADED
                     30: #ifndef DIRECT_THREADED
                     31: #define DIRECT_THREADED
                     32: #endif
                     33: #endif
                     34: 
                     35: #define FLUSH_ICACHE(addr,size)                asm("call_pal 0x86") /* imb (instruction-memory barrier) */
                     36: 
1.2       jwilke     37: #include "../generic/machine.h"
1.1       anton      38: 
                     39: #ifdef DIRECT_THREADED
                     40: #ifdef WORDS_BIGENDIAN
                     41: #error Direct threading only supported for little-endian Alphas.
                     42: /* big-endian Alphas still store instructions in little-endian format,
                     43:    so you would have to reverse the instruction accesses in the following
                     44: */
                     45: #endif
                     46: #if SIZEOF_CHAR_P != 8
                     47: #error Direct threading only supported for Alphas with 64-bit Cells.
                     48: /* some of the stuff below assumes that the first cell in a code field
                     49:    can contain 2 instructions
                     50: 
                     51:    A simple way around this problem would be to have _alpha_docol
                     52:    contain &&dodoes. This would slow down colon defs, however.
                     53: 
                     54:    Another way is to use a special DOES_HANDLER, like most other CPUs */
                     55: #endif
                     56: 
                     57: #warning Direct threading for Alpha may not work with all gcc versions
                     58: #warning ;CODE does not work on the Alpha with direct threading
                     59: /* ;CODE puts a jump to the code after ;CODE into the defined
                     60:    word. The code generated for the jump can only jump to targets near
                     61:    docol (near means: within 32KB). Because the code is far from
                     62:    docol, this does not work.
                     63: 
                     64:    Solution: let the code be: x=cfa[1]; goto *x;
                     65:    */
                     66: 
                     67: typedef int Int32;
                     68: typedef short Int16;
                     69: 
                     70: /* PFA gives the parameter field address corresponding to a cfa */
                     71: #define PFA(cfa)       (((Cell *)cfa)+2)
                     72: /* PFA1 is a special version for use just after a NEXT1 */
                     73: /* the improvement here is that we may destroy cfa before using PFA1 */
                     74: #define PFA1(cfa)       PFA(cfa)
                     75: 
                     76: /*
                     77:    On the Alpha, code (in the text segment) typically cannot be
                     78:    reached from the dictionary (in the data segment) with a normal
                     79:    branch. It also usually takes too long (and too much space on
                     80:    32-bit systems) to load the address as literal and jump indirectly.
                     81:    
                     82:    So, what we do is this: a pointer into our code (at docol, to be
                     83:    exact) is kept in a register: _alpha_docol. When the inner
                     84:    interpreter jumps to the word address of a variable etc., the
                     85:    destination address is computed from that with a lda instruction
                     86:    and stored in another register: _alpha_ca. Then an indirect jump
                     87:    through _alpha_ca is performed. For docol, we need not compute
                     88:    _alpha_ca first.
                     89: 
                     90:    How do we tell gcc all this? We declare the registers as variables:
                     91:    _alpha_docol as explicit variable, to avoid spilling; _alpha_ca is
                     92:    so short-lived, so it hopefully won't be spilled. A
                     93:    pseudo-primitive cpu_dep is created with code that lets gcc's data
                     94:    flow analysis know that _alpha_docol is used and that _alpha_ca may
                     95:    be defined and used after any NEXT and before any primitive.  We
                     96:    let gcc choose the register for _alpha_ca and simply change the
                     97:    code gcc produces for the cpu_dep routine.
                     98: */
                     99: 
                    100: #define CPU_DEP2       register Label _alpha_docol asm("$9")=&&docol; \
                    101:                        register Label _alpha_ca;
                    102: 
                    103: #define CPU_DEP3       cpu_dep: asm("lda %0, 500(%1)":"=r"(_alpha_ca):"r"(_alpha_docol)); goto *_alpha_ca;
                    104: 
                    105: #define CPU_DEP1       (&&cpu_dep)
                    106: 
                    107: 
                    108: /* CODE_ADDRESS is the address of the code jumped to through the code field */
                    109: #define CODE_ADDRESS(wa)       ({Int32 *_wa=(Int32 *)(wa); \
                    110:                                    (_wa[0]&0xfc000000)==0x68000000 ? /*JMP?*/\
                    111:                                    &&docol : \
                    112:                                    &&docol+((Int16 *)_wa)[0]; })
                    113: 
                    114: #define _CPU_DEP_LABEL (symbols[DOESJUMP])
                    115: #define _DOCOL_LABEL   (symbols[DOCOL])
                    116: 
                    117: /* MAKE_CF creates an appropriate code field at the wa; ca is the code
                    118:    address. For the Alpha, this is a lda followed by a jmp (or just a
                    119:    jmp, if ca==&&docol).  We patch the jmp with a good hint (on the
                    120:    21064A this saves 5 cycles!) */
                    121: #define MAKE_CF(wa,ca) ({ \
                    122:                             Int32 *_wa=(Int32 *)(wa); \
                    123:                             Label _ca=(Label)(ca); \
                    124:                             if (_ca==_DOCOL_LABEL)  \
                    125:                               _wa[0]=(((0x1a<<26)|(31<<21)|(9<<16))| \
                    126:                                       (((((Cell)_ca)-((Cell)_wa)-4) & 0xffff)>>2)); \
                    127:                             else { \
                    128:                               _wa[0]=((((Int32 *)_CPU_DEP_LABEL)[0] & 0xffff0000)| \
                    129:                                       ((((Cell)_ca)-((Cell)_DOCOL_LABEL)) & 0xffff)); \
                    130:                               _wa[1]=((((Int32 *)_CPU_DEP_LABEL)[1] & 0xffffc000)| \
                    131:                                       (((((Cell)_ca)-((Cell)_wa)-8) & 0xffff)>>2));  \
                    132:                             } \
                    133:                        })
                    134: 
                    135: /* this is the point where the does code for the word with the xt cfa
                    136:    starts. Because the jump to the code field takes only one cell on
                    137:    64-bit systems we can use the second cell of the cfa for storing
                    138:    the does address */
                    139: #define DOES_CODE(cfa) \
                    140:      ({ Int32 *_wa=(cfa); \
                    141:        (_wa[0] == ((((Int32 *)_CPU_DEP_LABEL)[0] & 0xffff0000)| \
                    142:                    ((((Cell)&&dodoes)-((Cell)&&docol)) & 0xffff)) && \
                    143:         (_wa[1]&0xffffc000) == (((Int32 *)_CPU_DEP_LABEL)[1] & 0xffffc000)) \
                    144:        ? DOES_CODE1(_wa) : 0; })
                    145: 
                    146: /* this is a special version of DOES_CODE for use in dodoes */
                    147: #define DOES_CODE1(cfa)        ((Xt *)(((Cell *)(cfa))[1]))
                    148: 
                    149: /* the does handler resides between DOES> and the following Forth
                    150:    code. Since the code-field jumps directly to dodoes, the
                    151:    does-handler is not needed for the Alpha architecture */
                    152: #define MAKE_DOES_HANDLER(addr)   0
                    153: 
                    154: /* This makes a code field for a does-defined word. doesp is the
                    155:    address of the does-code. On the Alpha, the code field consists of
                    156:    a jump to dodoes and the address of the does code */
                    157: #define MAKE_DOES_CF(cfa,doesp) ({Xt *_cfa = (Xt *)(cfa); \
                    158:                                    MAKE_CF(_cfa, symbols[DODOES]); \
                    159:                                    _cfa[1] = (doesp); })
                    160: #endif
                    161: 

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