blob: 3bcff9e5f0b3da01bdb873714f2d9e51602d6761 [file] [log] [blame]
[email protected]997e22222009-09-18 18:27:251#!/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 <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#
40set beforeUnion {} ;# C code before union
41set unionDef {} ;# C code of the union
42set afterUnion {} ;# C code after the union
43set sCtr 0 ;# Context counter
44
45# Read program text up to the spot where the union should be
46# inserted.
47#
48while {![eof stdin]} {
49 set line [gets stdin]
50 if {[regexp {INSERT STACK UNION HERE} $line]} break
51 append beforeUnion $line\n
52}
53
54# Process the remaining text. Build up the union definition as we go.
55#
56set vlist {}
57set seenDecl 0
58set namechars {abcdefghijklmnopqrstuvwxyz}
59set nnc [string length $namechars]
60while {![eof stdin]} {
61 set line [gets stdin]
62 if {[regexp "^case (OP_\\w+): \173" $line all operator]} {
63 append afterUnion $line\n
64 set vlist {}
65 while {![eof stdin]} {
66 set line [gets stdin]
67 if {[regexp {^ +(const )?\w+ \**(\w+)(\[.*\])?;} $line \
68 all constKeyword vname notused1]} {
69 if {!$seenDecl} {
70 set sname {}
71 append sname [string index $namechars [expr {$sCtr/$nnc}]]
72 append sname [string index $namechars [expr {$sCtr%$nnc}]]
73 incr sCtr
74 append unionDef " struct ${operator}_stack_vars \173\n"
75 append afterUnion \
76 "#if 0 /* local variables moved into u.$sname */\n"
77 set seenDecl 1
78 }
79 append unionDef " $line\n"
80 append afterUnion $line\n
81 lappend vlist $vname
82 } else {
83 break
84 }
85 }
86 if {$seenDecl} {
87 append unionDef " \175 $sname;\n"
88 append afterUnion "#endif /* local variables moved into u.$sname */\n"
89 }
90 set seenDecl 0
91 }
92 if {[regexp "^\175" $line]} {
93 append afterUnion $line\n
94 set vlist {}
95 } elseif {[llength $vlist]>0} {
96 append line " "
97 foreach v $vlist {
98 regsub -all "(\[^a-zA-Z0-9>.\])${v}(\\W)" $line "\\1u.$sname.$v\\2" line
99 regsub -all "(\[^a-zA-Z0-9>.\])${v}(\\W)" $line "\\1u.$sname.$v\\2" line
100 }
101 append afterUnion [string trimright $line]\n
102 } elseif {$line=="" && [eof stdin]} {
103 # no-op
104 } else {
105 append afterUnion $line\n
106 }
107}
108
109# Output the resulting text.
110#
111puts -nonewline $beforeUnion
112puts " /********************************************************************"
113puts " ** Automatically generated code"
114puts " **"
115puts " ** The following union is automatically generated by the"
116puts " ** vdbe-compress.tcl script. The purpose of this union is to"
117puts " ** reduce the amount of stack space required by this function."
118puts " ** See comments in the vdbe-compress.tcl script for details."
119puts " */"
120puts " union vdbeExecUnion \173"
121puts -nonewline $unionDef
122puts " \175 u;"
123puts " /* End automatically generated code"
124puts " ********************************************************************/"
125puts -nonewline $afterUnion