Speedup regexp compilation if not using dfa.

2 files changed, 14 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index f218714f..9e5167e4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2016-08-14         Arnold D. Robbins     <arnold@skeeve.com>
+
+	* re.c (make_regexp): Only call dfasyntax if actually using
+	dfa. Gives a 14% speedup on this test: https://raw.githubusercontent.com/chadbrewbaker/awka/master/benchmark/regexp.awk.
+	From blathering in comp.lang.awk.
+
 2016-08-12         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* dfa.c: Sync with GNU grep.
diff --git a/re.c b/re.c
index 5049bca6..8a325308 100644
--- a/re.c
+++ b/re.c
@@ -203,10 +203,14 @@ make_regexp(const char *s, size_t len, bool ignorecase, bool dfa, bool canfatal)
 		syn &= ~RE_ICASE;
 	}
 
-	dfa_syn = syn;
-	if (ignorecase)
-		dfa_syn |= RE_ICASE;
-	dfasyntax(dfa_syn, ignorecase, '\n');
+	/* only call dfasyntax if we're using dfa; saves time */
+	if (dfa && ! no_dfa) {
+		dfa_syn = syn;
+		/* FIXME: dfa doesn't pay attention RE_ICASE */
+		if (ignorecase)
+			dfa_syn |= RE_ICASE;
+		dfasyntax(dfa_syn, ignorecase, '\n');
+	}
 	re_set_syntax(syn);
 
 	if ((rerr = re_compile_pattern(buf, len, &(rp->pat))) != NULL) {