From ab4c3a0c5ee5b18a41bdc2ba39ca9d057398b5b2 Mon Sep 17 00:00:00 2001
From: Randy Heit <rheit@users.noreply.github.com>
Date: Sun, 20 Mar 2016 10:53:42 -0500
Subject: [PATCH] Lemon update 2016-02-17 01:46:19 on branch parser-performance

- Further improvements to the Lemon-generated code for yy_reduce(). (user: drh)
---
 tools/lemon/lemon.c  | 18 +++++++++++++-----
 tools/lemon/lempar.c |  2 --
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/tools/lemon/lemon.c b/tools/lemon/lemon.c
index 7eb72b6524..b32c032b6b 100644
--- a/tools/lemon/lemon.c
+++ b/tools/lemon/lemon.c
@@ -3404,10 +3404,14 @@ PRIVATE char *append_str(const char *zText, int n, int p1, int p2, int bNoSubst)
 ** zCode is a string that is the action associated with a rule.  Expand
 ** the symbols in this string so that the refer to elements of the parser
 ** stack.
+**
+** Return 1 if the expanded code requires that "yylhsminor" local variable
+** to be defined.
 */
-PRIVATE void translate_code(struct lemon *lemp, struct rule *rp){
+PRIVATE int translate_code(struct lemon *lemp, struct rule *rp){
   char *cp, *xp;
   int i;
+  int rc = 0;          /* True if yylhsminor is used */
   char lhsused = 0;    /* True if the LHS element has been used */
   char lhsdirect;      /* True if LHS writes directly into stack */
   char used[MAXRHS];   /* True for each RHS element which is used */
@@ -3457,9 +3461,7 @@ PRIVATE void translate_code(struct lemon *lemp, struct rule *rp){
   if( lhsdirect ){
     sprintf(zLhs, "yymsp[%d].minor.yy%d",1-rp->nrhs,rp->lhs->dtnum);
   }else{
-    append_str(0,0,0,0,0);
-    append_str("  YYMINORTYPE yylhsminor;\n", 0, 0, 0, 0);
-    rp->codePrefix = Strsafe(append_str(0,0,0,0,0));
+    rc = 1;
     sprintf(zLhs, "yylhsminor.yy%d",rp->lhs->dtnum);
   }
 
@@ -3564,6 +3566,8 @@ PRIVATE void translate_code(struct lemon *lemp, struct rule *rp){
   /* Suffix code generation complete */
   cp = append_str(0,0,0,0,0);
   if( cp ) rp->codeSuffix = Strsafe(cp);
+
+  return rc;
 }
 
 /* 
@@ -4232,9 +4236,13 @@ void ReportTable(
   tplt_xfer(lemp->name,in,out,&lineno);
 
   /* Generate code which executes during each REDUCE action */
+  i = 0;
   for(rp=lemp->rule; rp; rp=rp->next){
-    translate_code(lemp, rp);
+    i += translate_code(lemp, rp);
   }
+  if( i ){
+    fprintf(out,"        YYMINORTYPE yylhsminor;\n"); lineno++;
+   }
   /* First output rules other than the default: rule */
   for(rp=lemp->rule; rp; rp=rp->next){
     struct rule *rp2;               /* Other rules with the same action */
diff --git a/tools/lemon/lempar.c b/tools/lemon/lempar.c
index b3ab0da067..25ac970367 100644
--- a/tools/lemon/lempar.c
+++ b/tools/lemon/lempar.c
@@ -636,8 +636,6 @@ static void yy_reduce(
   }
 #endif /* NDEBUG */
 
-  /*  yygotominor = yyzerominor; */
-
   /* Check that the stack is large enough to grow by a single entry
   ** if the RHS of the rule is empty.  This ensures that there is room
   ** enough on the stack to push the LHS value */