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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Artifact 165780c5d75f55fbfa02ed9bedb6eef74b9d81da:


#!/usr/bin/awk -f
#
# Generate the file opcodes.h.
#
# This AWK script scans a concatenation of the parse.h output file from the
# parser and the vdbe.c source file in order to generate the opcodes numbers
# for all opcodes.  
#
# The lines of the vdbe.c that we are interested in are of the form:
#
#       case OP_aaaa:      /* same as TK_bbbbb */
#
# The TK_ comment is optional.  If it is present, then the value assigned to
# the OP_ is the same as the TK_ value.  If missing, the OP_ value is assigned
# a small integer that is different from every other OP_ value.
#
# We go to the trouble of making some OP_ values the same as TK_ values
# as an optimization.  During parsing, things like expression operators
# are coded with TK_ values such as TK_ADD, TK_DIVIDE, and so forth.  Later
# during code generation, we need to generate corresponding opcodes like
# OP_Add and OP_Divide.  By making TK_ADD==OP_Add and TK_DIVIDE==OP_Divide,
# code to translate from one to the other is avoided.  This makes the
# code generator run (infinitesimally) faster and more importantly it makes
# the library footprint smaller.
#
# This script also scans for lines of the form:
#
#       case OP_aaaa:       /* no-push */
#
# When the no-push comment is found on an opcode, it means that that
# opcode does not leave a result on the stack.  By identifying which
# opcodes leave results on the stack it is possible to determine a
# much smaller upper bound on the size of the stack.  This allows
# a smaller stack to be allocated, which is important to embedded
# systems with limited memory space.  This script generates a series
# of "NOPUSH_MASK" defines that contain bitmaps of opcodes that leave
# results on the stack.  The NOPUSH_MASK defines are used in vdbeaux.c
# to help determine the maximum stack size.
#


# Remember the TK_ values from the parse.h file
/^#define TK_/ {
  tk[$2] = 0+$3
}

# Scan for "case OP_aaaa:" lines in the vdbe.c file
/^case OP_/ {
  name = $2
  sub(/:/,"",name)
  sub("\r","",name)
  op[name] = -1
  jump[name] = 0
  nopush[name] = 0
  out2_prerelease[name] = 0
  in1[name] = 0
  in2[name] = 0
  in3[name] = 0
  out2[name] = 0
  out3[name] = 0
  for(i=3; i<NF; i++){
    if($i=="same" && $(i+1)=="as"){
      sym = $(i+2)
      sub(/,/,"",sym)
      op[name] = tk[sym]
      used[op[name]] = 1
      sameas[op[name]] = sym
    }
    x = $i
    sub(",","",x)
    if(x=="no-push"){
      nopush[name] = 1
    }else if(x=="jump"){
      jump[name] = 1
    }else if(x=="out2-prerelease"){
      out2_prerelease[name] = 1
    }else if(x=="in1"){
      in1[name] = 1
    }else if(x=="in2"){
      in2[name] = 1
    }else if(x=="in3"){
      in3[name] = 1
    }else if(x=="out2"){
      out2[name] = 1
    }else if(x=="out3"){
      out3[name] = 1
    }
  }
}

# Assign numbers to all opcodes and output the result.
END {
  cnt = 0
  max = 0
  print "/* Automatically generated.  Do not edit */"
  print "/* See the mkopcodeh.awk script for details */"
  for(name in op){
    if( op[name]<0 ){
      cnt++
      while( used[cnt] ) cnt++
      op[name] = cnt
    }
    used[op[name]] = 1;
    if( op[name]>max ) max = op[name]
    printf "#define %-25s %15d", name, op[name]
    if( sameas[op[name]] ) {
      printf "   /* same as %-12s*/", sameas[op[name]]
    } 
    printf "\n"

  }
  seenUnused = 0;
  for(i=1; i<max; i++){
    if( !used[i] ){
      if( !seenUnused ){
        printf "\n/* The following opcode values are never used */\n"
        seenUnused = 1
      }
      printf "#define %-25s %15d\n", sprintf( "OP_NotUsed_%-3d", i ), i
    }
  }

  # Generate the bitvectors:
  #
  #  bit 0:     jump
  #  bit 1:     pushes a result onto stack
  #  bit 2:     output to p1.  release p1 before opcode runs
  #
  for(i=0; i<=max; i++) bv[i] = 0;
  for(name in op){
    x = op[name]
    a0 = a1 = a2 = a3 = a4 = a5 = a6 = a7 = 0
    a8 = a9 = a10 = a11 = a12 = a13 = a14 = a15 = 0
    if( jump[name] ) a0 = 1;
    if( nopush[name]==0 ) a1 = 2;
    if( out2_prerelease[name] ) a2 = 4;
    if( in1[name] ) a3 = 8;
    if( in2[name] ) a4 = 16;
    if( in3[name] ) a5 = 32;
    if( out2[name] ) a6 = 64;
    if( out3[name] ) a7 = 128;
    bv[x] = a0+a1+a2+a3+a4+a5+a6+a7+a8+a9+a10+a11+a12+a13+a14+a15;
  }
  print "\n"
  print "/* Properties such as \"out2\" or \"jump\" that are specified in"
  print "** comments following the "case" for each opcode in the vdbe.c"
  print "** are encoded into bitvectors as follows:"
  print "*/"
  print "#define OPFLG_JUMP            0x0001  /* jump:  P2 holds jmp target */"
  print "#define OPFLG_PUSH            0x0002  /* ~no-push:  Does not push */"
  print "#define OPFLG_OUT2_PRERELEASE 0x0004  /* out2-prerelease: */"
  print "#define OPFLG_IN1             0x0008  /* in1:   P1 is an input */"
  print "#define OPFLG_IN2             0x0010  /* in2:   P2 is an input */"
  print "#define OPFLG_IN3             0x0020  /* in3:   P3 is an input */"
  print "#define OPFLG_OUT2            0x0040  /* out2:  P2 is an output */"
  print "#define OPFLG_OUT3            0x0080  /* out3:  P3 is an output */"
  print "#define OPFLG_INITIALIZER {\\"
  for(i=0; i<=max; i++){
    if( i%8==0 ) printf("/* %3d */",i)
    printf " 0x%04x,", bv[i]
    if( i%8==7 ) printf("\\\n");
  }
  print "}"
}