GCC's bacl-end & assemble emission (47)

17.   Toolof gencheck

Program after processing by front-end, is transformed into rtl form.Program in this intermediate form is constructed as a tree. Can conceive thatthe nodes in the tree are various and complex, to put node creation in easierand more controllable way. Nodes are described in tree.def and C-common.def(file specified for c & c++) similar as rtx object in rtl.def.

The instruction used to describe tree nodes is in following form.

DEFTREECODE(SYM, NAME, TYPE, LENGTH)

For example in tree.def, we can get following lines.

DEFTREECODE (IDENTIFIER_NODE,"identifier_node", 'x', 0)

In gencheck.c we can see below code snippet.

 

27    #define DEFTREECODE(SYM, NAME, TYPE, LEN) #SYM,                       in gencheck.c

28   

29    static const char *const tree_codes[] = {

30    #include "tree.def"

31    #include "c-common.def"

32    #include "gencheck.h"

33    (char*) 0

34    };

 

At line 32 above, gencheck.h will be created by Makefile which willinclude appropriate def files according to the target language.

 

44    int

45    main (int argc, char **argvATTRIBUTE_UNUSED)                                           in gencheck.c

46    {

47     int i, j;

48   

49     switch (argc)

50     {

51       case 1:

52         break;

53   

54       default:

55         usage ();

56         return (1);

57     }

58   

59     puts ("/* This file is generated using gencheck. Do not edit.*/\n");

60     puts ("#ifndef GCC_TREE_CHECK_H");

61     puts ("#define GCC_TREE_CHECK_H\n");

62   

63     /* Print macros for checks based on each ofthe tree code names. However,

64        since we include the tree nodes from alllanguages, we must check

65        for duplicate names to avoid defining thesame macro twice.  */

66      for(i = 0; tree_codes[i];i++)

67      {

68        for(j = 0; j < i; j++)

69         if (strcmp (tree_codes[i], tree_codes[j]) == 0)

70            break;

71   

72       if (i == j)

73         printf ("#define %s_CHECK(t)\tTREE_CHECK (t, %s)\n",

74                tree_codes[i], tree_codes[i]);

75     }

76   

77     puts ("\n#endif /* GCC_TREE_CHECK_H */");

78     return 0;

79    }

 

Then as for IDENTIFIER_NODE, following code will be output intotree-check.h

 

#define IDENTIFIER_NODE_CHECK(t)    TREE_CHECK (t, IDENTIFIER_NODE)

18.   Toolof genconstants

The tool will output insn-constants.h defining constants used inmachine description file.

 

52    int

53    main (int argc, char **argv)                                                                 ingenconstants.c

54    {

55     int dummy1, dummy2;

56     rtx desc;

57   

58     progname= "genconstants";

59   

60     if (argc <= 1)

61       fatal ("no input file name");

62   

63     if (init_md_reader (argv[1]) != SUCCESS_EXIT_CODE)

64       return (FATAL_EXIT_CODE);

65   

66     /* Scan and discard the entire file. This hasthe side effect

67        of loading up the constants table that wewish to scan.  */

68     do

69       desc = read_md_rtx (&dummy1,&dummy2);

70     while (desc);

71   

72     puts ("/* Generated automatically by the program`genconstants'");

73     puts ("   from the machinedescription file `md'.  */\n");

74      puts ("#ifndef GCC_INSN_CONSTANTS_H");

75      puts ("#defineGCC_INSN_CONSTANTS_H\n");

76   

77      traverse_md_constants (print_md_constant, stdout);

78   

79      puts ("\n#endif /*GCC_INSN_CONSTANTS_H */");

80   

81      if (ferror (stdout) || fflush(stdout) || fclose (stdout))

82       return FATAL_EXIT_CODE;

83   

84     return SUCCESS_EXIT_CODE;

85    }

 

477  void

478  traverse_md_constants (htab_trav callback, void *info)                                  inread-rtl.c

479  {

480   if (md_constants)

481     htab_traverse (md_constants, callback, info);

482  }

 

In i386.md, it uses define_constants to define constants to be used.md_constantsabove records the constants read by read_constants.