tool/vdbe-compress.tcl

   1 #!/usr/bin/tcl
   2 #
   3 # This script makes modifications to the vdbe.c source file which reduce
   4 # the amount of stack space required by the sqlite3VdbeExec() routine.
   5 #
   6 # The modifications performed by this script are optional.  The vdbe.c
   7 # source file will compile correctly with and without the modifications
   8 # performed by this script.  And all routines within vdbe.c will compute
   9 # the same result.  The modifications made by this script merely help
  10 # the C compiler to generate code for sqlite3VdbeExec() that uses less
  11 # stack space.
  12 #
  13 # Script usage:
  14 #
  15 #          mv vdbe.c vdbe.c.template
  16 #          tclsh vdbe-compress.tcl $CFLAGS <vdbe.c.template >vdbe.c
  17 #
  18 # Modifications made:
  19 #
  20 # All modifications are within the sqlite3VdbeExec() function.  The
  21 # modifications seek to reduce the amount of stack space allocated by
  22 # this routine by moving local variable declarations out of individual
  23 # opcode implementations and into a single large union.  The union contains
  24 # a separate structure for each opcode and that structure contains the
  25 # local variables used by that opcode.  In this way, the total amount
  26 # of stack space required by sqlite3VdbeExec() is reduced from the
  27 # sum of all local variables to the maximum of the local variable space
  28 # required for any single opcode.
  29 #
  30 # In order to be recognized by this script, local variables must appear
  31 # on the first line after the open curly-brace that begins a new opcode
  32 # implementation.  Local variables must not have initializers, though they
  33 # may be commented.
  34 #
  35 # The union definition is inserted in place of a special marker comment
  36 # in the preamble to the sqlite3VdbeExec() implementation.
  37 #
  38 #############################################################################
  39 #
  40 set beforeUnion {}   ;# C code before union
  41 set unionDef {}      ;# C code of the union
  42 set afterUnion {}    ;# C code after the union
  43 set sCtr 0           ;# Context counter
  44
  45 # If the SQLITE_SMALL_STACK compile-time option is missing, then
  46 # this transformation becomes a no-op.
  47 #
  48 if {![regexp {SQLITE_SMALL_STACK} $argv]} {
  49   while {![eof stdin]} {
  50     puts [gets stdin]
  51   }
  52   exit
  53 }
  54
  55 # Read program text up to the spot where the union should be
  56 # inserted.
  57 #
  58 while {![eof stdin]} {
  59   set line [gets stdin]
  60   if {[regexp {INSERT STACK UNION HERE} $line]} break
  61   append beforeUnion $line\n
  62 }
  63
  64 # Process the remaining text.  Build up the union definition as we go.
  65 #
  66 set vlist {}
  67 set seenDecl 0
  68 set namechars {abcefghjklmnopqrstuvwxyz}
  69 set nnc [string length $namechars]
  70 while {![eof stdin]} {
  71   set line [gets stdin]
  72   if {[regexp "^case (OP_\\w+): \173" $line all operator]} {
  73     append afterUnion $line\n
  74     set vlist {}
  75     while {![eof stdin]} {
  76       set line [gets stdin]
  77       if {[regexp {^ +(const )?\w+ \**(\w+)(\[.*\])?;} $line \
  78            all constKeyword vname notused1]} {
  79         if {!$seenDecl} {
  80           set sname {}
  81           append sname [string index $namechars [expr {$sCtr/$nnc}]]
  82           append sname [string index $namechars [expr {$sCtr%$nnc}]]
  83           incr sCtr
  84           append unionDef "    struct ${operator}_stack_vars \173\n"
  85           append afterUnion \
  86              "#if 0  /* local variables moved into u.$sname */\n"
  87           set seenDecl 1
  88         }
  89         append unionDef "    $line\n"
  90         append afterUnion $line\n
  91         lappend vlist $vname
  92       } elseif {[regexp {^#(if|endif)} $line] && [llength $vlist]>0} {
  93         append unionDef "$line\n"
  94         append afterUnion $line\n
  95       } else {
  96         break
  97       }
  98     }
  99     if {$seenDecl} {
 100       append unionDef   "    \175 $sname;\n"
 101       append afterUnion "#endif /* local variables moved into u.$sname */\n"
 102     }
 103     set seenDecl 0
 104   }
 105   if {[regexp "^\175" $line]} {
 106     append afterUnion $line\n
 107     set vlist {}
 108   } elseif {[llength $vlist]>0} {
 109     append line " "
 110     foreach v $vlist {
 111       regsub -all "(\[^a-zA-Z0-9>.\])${v}(\\W)" $line "\\1u.$sname.$v\\2" line
 112       regsub -all "(\[^a-zA-Z0-9>.\])${v}(\\W)" $line "\\1u.$sname.$v\\2" line
 113
 114       # The expressions above fail to catch instance of variable "abc" in
 115       # expressions like (32>abc). The following expression makes those
 116       # substitutions.
 117       regsub -all "(\[^-\])>${v}(\\W)" $line "\\1>u.$sname.$v\\2" line
 118     }
 119     append afterUnion [string trimright $line]\n
 120   } elseif {$line=="" && [eof stdin]} {
 121     # no-op
 122   } else {
 123     append afterUnion $line\n
 124   }
 125 }
 126
 127 # Output the resulting text.
 128 #
 129 puts -nonewline $beforeUnion
 130 puts "  /********************************************************************"
 131 puts "  ** Automatically generated code"
 132 puts "  **"
 133 puts "  ** The following union is automatically generated by the"
 134 puts "  ** vdbe-compress.tcl script.  The purpose of this union is to"
 135 puts "  ** reduce the amount of stack space required by this function."
 136 puts "  ** See comments in the vdbe-compress.tcl script for details."
 137 puts "  */"
 138 puts "  union vdbeExecUnion \173"
 139 puts -nonewline $unionDef
 140 puts "  \175 u;"
 141 puts "  /* End automatically generated code"
 142 puts "  ********************************************************************/"
 143 puts -nonewline $afterUnion