builtins.c: Fix a trivial typo in a comment.

gcc/ChangeLog:
	* builtins.c: Fix a trivial typo in a comment.

From-SVN: r247623

gcc/ChangeLog

 2017-05-04  Martin Sebor  <msebor@redhat.com>
 
+	* builtins.c: Fix a trivial typo in a comment.
+
 	PR middle-end/79234
 	* builtins.c (check_sizes): Adjust to handle reading past the end.
 	Avoid printing excessive upper bound of ranges.  Use %E to print

gcc/builtins.c

@@ -3047,7 +3047,7 @@ expand_builtin_memcpy_args (tree dest, tree src, tree len, rtx target, tree exp)
    MAXLEN is the user-supplied bound on the length of the source sequence
    (such as in strncat(d, s, N).  It specifies the upper limit on the number
    of bytes to write.
-   SRC is the source string (such as in strcpy(d, s)) when the epxression
+   SRC is the source string (such as in strcpy(d, s)) when the expression
    EXP is a string function call (as opposed to a memory call like memcpy).
    As an exception, SRC can also be an integer denoting the precomputed
    size of the source string or object (for functions like memcpy).