diff --git a/lib/Support/regengine.inc b/lib/Support/regengine.inc
index 0f27cfd4b5b..bf55543dab8 100644
--- a/lib/Support/regengine.inc
+++ b/lib/Support/regengine.inc
@@ -72,11 +72,11 @@ struct match {
 	struct re_guts *g;
 	int eflags;
 	llvm_regmatch_t *pmatch;	/* [nsub+1] (0 element unused) */
-	char *offp;		/* offsets work from here */
-	char *beginp;		/* start of string -- virtual NUL precedes */
-	char *endp;		/* end of string -- virtual NUL here */
-	char *coldp;		/* can be no match starting before here */
-	char **lastpos;		/* [nplus+1] */
+	const char *offp;		/* offsets work from here */
+	const char *beginp;		/* start of string -- virtual NUL precedes */
+	const char *endp;		/* end of string -- virtual NUL here */
+	const char *coldp;		/* can be no match starting before here */
+	const char **lastpos;		/* [nplus+1] */
 	STATEVARS;
 	states st;		/* current states */
 	states fresh;		/* states for a fresh start */
@@ -84,11 +84,14 @@ struct match {
 	states empty;		/* empty set of states */
 };
 
-static int matcher(struct re_guts *, char *, size_t, llvm_regmatch_t[], int);
-static char *dissect(struct match *, char *, char *, sopno, sopno);
-static char *backref(struct match *, char *, char *, sopno, sopno, sopno, int);
-static char *fast(struct match *, char *, char *, sopno, sopno);
-static char *slow(struct match *, char *, char *, sopno, sopno);
+static int matcher(struct re_guts *, const char *, size_t,
+                   llvm_regmatch_t[], int);
+static const char *dissect(struct match *, const char *, const char *, sopno,
+                           sopno);
+static const char *backref(struct match *, const char *, const char *, sopno,
+                           sopno, sopno, int);
+static const char *fast(struct match *, const char *, const char *, sopno, sopno);
+static const char *slow(struct match *, const char *, const char *, sopno, sopno);
 static states step(struct re_guts *, sopno, sopno, states, int, states);
 #define MAX_RECURSION	100
 #define	BOL	(OUT+1)
@@ -125,18 +128,19 @@ static int nope = 0;
  - matcher - the actual matching engine
  */
 static int			/* 0 success, REG_NOMATCH failure */
-matcher(struct re_guts *g, char *string, size_t nmatch, llvm_regmatch_t pmatch[],
+matcher(struct re_guts *g, const char *string, size_t nmatch,
+        llvm_regmatch_t pmatch[],
     int eflags)
 {
-	char *endp;
+	const char *endp;
 	size_t i;
 	struct match mv;
 	struct match *m = &mv;
-	char *dp;
+	const char *dp;
 	const sopno gf = g->firststate+1;	/* +1 for OEND */
 	const sopno gl = g->laststate;
-	char *start;
-	char *stop;
+	const char *start;
+	const char *stop;
 
 	/* simplify the situation where possible */
 	if (g->cflags&REG_NOSUB)
@@ -216,7 +220,7 @@ matcher(struct re_guts *g, char *string, size_t nmatch, llvm_regmatch_t pmatch[]
 			dp = dissect(m, m->coldp, endp, gf, gl);
 		} else {
 			if (g->nplus > 0 && m->lastpos == NULL)
-				m->lastpos = (char **)malloc((g->nplus+1) *
+				m->lastpos = (const char **)malloc((g->nplus+1) *
 							sizeof(char *));
 			if (g->nplus > 0 && m->lastpos == NULL) {
 				free(m->pmatch);
@@ -287,21 +291,22 @@ matcher(struct re_guts *g, char *string, size_t nmatch, llvm_regmatch_t pmatch[]
 /*
  - dissect - figure out what matched what, no back references
  */
-static char *			/* == stop (success) always */
-dissect(struct match *m, char *start, char *stop, sopno startst, sopno stopst)
+static const char *			/* == stop (success) always */
+dissect(struct match *m, const char *start, const char *stop, sopno startst,
+        sopno stopst)
 {
 	int i;
 	sopno ss;	/* start sop of current subRE */
 	sopno es;	/* end sop of current subRE */
-	char *sp;	/* start of string matched by it */
-	char *stp;	/* string matched by it cannot pass here */
-	char *rest;	/* start of rest of string */
-	char *tail;	/* string unmatched by rest of RE */
+	const char *sp;	/* start of string matched by it */
+	const char *stp;	/* string matched by it cannot pass here */
+	const char *rest;	/* start of rest of string */
+	const char *tail;	/* string unmatched by rest of RE */
 	sopno ssub;	/* start sop of subsubRE */
 	sopno esub;	/* end sop of subsubRE */
-	char *ssp;	/* start of string matched by subsubRE */
-	char *sep;	/* end of string matched by subsubRE */
-	char *oldssp;	/* previous ssp */
+	const char *ssp;	/* start of string matched by subsubRE */
+	const char *sep;	/* end of string matched by subsubRE */
+	const char *oldssp;	/* previous ssp */
 
 	AT("diss", start, stop, startst, stopst);
 	sp = start;
@@ -360,7 +365,7 @@ dissect(struct match *m, char *start, char *stop, sopno startst, sopno stopst)
 			esub = es - 1;
 			/* did innards match? */
 			if (slow(m, sp, rest, ssub, esub) != NULL) {
-				char *dp = dissect(m, sp, rest, ssub, esub);
+				const char *dp = dissect(m, sp, rest, ssub, esub);
 				(void)dp; /* avoid warning if assertions off */
 				assert(dp == rest);
 			} else		/* no */
@@ -400,7 +405,7 @@ dissect(struct match *m, char *start, char *stop, sopno startst, sopno stopst)
 			assert(sep == rest);	/* must exhaust substring */
 			assert(slow(m, ssp, sep, ssub, esub) == rest);
 			{
-				char *dp = dissect(m, ssp, sep, ssub, esub);
+				const char *dp = dissect(m, ssp, sep, ssub, esub);
 				(void)dp; /* avoid warning if assertions off */
 				assert(dp == sep);
 			}
@@ -438,7 +443,7 @@ dissect(struct match *m, char *start, char *stop, sopno startst, sopno stopst)
 					assert(OP(m->g->strip[esub]) == O_CH);
 			}
 			{
-				char *dp = dissect(m, sp, rest, ssub, esub);
+				const char *dp = dissect(m, sp, rest, ssub, esub);
 				(void)dp; /* avoid warning if assertions off */
 				assert(dp == rest);
 			}
@@ -474,17 +479,17 @@ dissect(struct match *m, char *start, char *stop, sopno startst, sopno stopst)
 /*
  - backref - figure out what matched what, figuring in back references
  */
-static char *			/* == stop (success) or NULL (failure) */
-backref(struct match *m, char *start, char *stop, sopno startst, sopno stopst,
-    sopno lev, int rec)			/* PLUS nesting level */
+static const char *			/* == stop (success) or NULL (failure) */
+backref(struct match *m, const char *start, const char *stop, sopno startst,
+        sopno stopst, sopno lev, int rec)			/* PLUS nesting level */
 {
 	int i;
 	sopno ss;	/* start sop of current subRE */
-	char *sp;	/* start of string matched by it */
+	const char *sp;	/* start of string matched by it */
 	sopno ssub;	/* start sop of subsubRE */
 	sopno esub;	/* end sop of subsubRE */
-	char *ssp;	/* start of string matched by subsubRE */
-	char *dp;
+	const char *ssp;	/* start of string matched by subsubRE */
+	const char *dp;
 	size_t len;
 	int hard;
 	sop s;
@@ -674,18 +679,19 @@ backref(struct match *m, char *start, char *stop, sopno startst, sopno stopst,
 /*
  - fast - step through the string at top speed
  */
-static char *			/* where tentative match ended, or NULL */
-fast(struct match *m, char *start, char *stop, sopno startst, sopno stopst)
+static const char *			/* where tentative match ended, or NULL */
+fast(struct match *m, const char *start, const char *stop, sopno startst,
+     sopno stopst)
 {
 	states st = m->st;
 	states fresh = m->fresh;
 	states tmp = m->tmp;
-	char *p = start;
+	const char *p = start;
 	int c = (start == m->beginp) ? OUT : *(start-1);
 	int lastc;	/* previous c */
 	int flagch;
 	int i;
-	char *coldp;	/* last p after which no match was underway */
+	const char *coldp;	/* last p after which no match was underway */
 
 	CLEAR(st);
 	SET1(st, startst);
@@ -758,18 +764,19 @@ fast(struct match *m, char *start, char *stop, sopno startst, sopno stopst)
 /*
  - slow - step through the string more deliberately
  */
-static char *			/* where it ended */
-slow(struct match *m, char *start, char *stop, sopno startst, sopno stopst)
+static const char *			/* where it ended */
+slow(struct match *m, const char *start, const char *stop, sopno startst,
+     sopno stopst)
 {
 	states st = m->st;
 	states empty = m->empty;
 	states tmp = m->tmp;
-	char *p = start;
+	const char *p = start;
 	int c = (start == m->beginp) ? OUT : *(start-1);
 	int lastc;	/* previous c */
 	int flagch;
 	int i;
-	char *matchp;	/* last p at which a match ended */
+	const char *matchp;	/* last p at which a match ended */
 
 	AT("slow", start, stop, startst, stopst);
 	CLEAR(st);
diff --git a/lib/Support/regexec.c b/lib/Support/regexec.c
index 7d70f6e16c7..41fb2ea46c9 100644
--- a/lib/Support/regexec.c
+++ b/lib/Support/regexec.c
@@ -155,7 +155,7 @@ llvm_regexec(const llvm_regex_t *preg, const char *string, size_t nmatch,
 	eflags = GOODFLAGS(eflags);
 
 	if (g->nstates <= (long)(CHAR_BIT*sizeof(states1)) && !(eflags&REG_LARGE))
-		return(smatcher(g, (char *)string, nmatch, pmatch, eflags));
+		return(smatcher(g, string, nmatch, pmatch, eflags));
 	else
-		return(lmatcher(g, (char *)string, nmatch, pmatch, eflags));
+		return(lmatcher(g, string, nmatch, pmatch, eflags));
 }