1 files changed, 31 insertions, 1 deletions
diff --git a/ext/pdo_sqlite/sqlite/mkopcodeh.awk b/ext/pdo_sqlite/sqlite/mkopcodeh.awk
index ead07d5ff9..641b987a81 100644
--- a/ext/pdo_sqlite/sqlite/mkopcodeh.awk
+++ b/ext/pdo_sqlite/sqlite/mkopcodeh.awk
@@ -1,5 +1,7 @@
 #!/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.  
@@ -12,6 +14,15 @@
 # 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_ value 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 translation from one to the other is avoided.  This makes the
+# code generator run (infinitesimally) faster and more importantly it makes
+# the total library smaller.
+#
 
 # Remember the TK_ values from the parse.h file
 /^#define TK_/ {
@@ -28,6 +39,7 @@
     if($i=="same" && $(i+1)=="as"){
       op[name] = tk[$(i+2)]
       used[op[name]] = 1
+      sameas[op[name]] = $(i+2)
     }
   }
 }
@@ -35,6 +47,7 @@
 # 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){
@@ -43,6 +56,23 @@ END {
       while( used[cnt] ) cnt++
       op[name] = cnt
     }
-    printf "#define %-30s %d\n", name, op[name]
+    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
+    }
   }
 }