[src/trunk]: src/usr.bin/make make(1): replace strstr in ParseMaybeSubMake wi...

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/38bdf4742859
branches:  trunk
changeset: 956797:38bdf4742859
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sat Nov 07 23:41:38 2020 +0000

description:
make(1): replace strstr in ParseMaybeSubMake with optimized code

This code is called for each command that is parsed.  Calling strstr with
4 strings that all start with the same character is unnecessary work.
Therefore, replace strstr with manually optimized code.  Neither GCC
5.5.0 nor GCC 10 inlines strncmp like this, otherwise I would have used
that.

Change in behavior: previously, a${MAKE}b would not be considered to be a
sub-make command, which is probably correct but does not occur in
practice.  The check for non-alphanumeric characters around the found
string was probably meant only for the plain word "make".

diffstat:

 usr.bin/make/parse.c |  65 ++++++++++++++++++++++++++++------------------------
 1 files changed, 35 insertions(+), 30 deletions(-)

diffs (96 lines):

diff -r 5455baa62703 -r 38bdf4742859 usr.bin/make/parse.c
--- a/usr.bin/make/parse.c      Sat Nov 07 23:25:06 2020 +0000
+++ b/usr.bin/make/parse.c      Sat Nov 07 23:41:38 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: parse.c,v 1.431 2020/11/07 22:26:42 rillig Exp $       */
+/*     $NetBSD: parse.c,v 1.432 2020/11/07 23:41:38 rillig Exp $       */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -117,7 +117,7 @@
 #include "pathnames.h"
 
 /*     "@(#)parse.c    8.3 (Berkeley) 3/19/94" */
-MAKE_RCSID("$NetBSD: parse.c,v 1.431 2020/11/07 22:26:42 rillig Exp $");
+MAKE_RCSID("$NetBSD: parse.c,v 1.432 2020/11/07 23:41:38 rillig Exp $");
 
 /* types and constants */
 
@@ -2031,36 +2031,41 @@
 }
 
 
-/*
- * ParseMaybeSubMake --
- *     Scan the command string to see if it a possible submake node
- * Input:
- *     cmd             the command to scan
- * Results:
- *     TRUE if the command is possibly a submake, FALSE if not.
- */
+/* See if the command possibly calls a sub-make by using the variable
+ * expressions ${.MAKE}, ${MAKE} or the plain word "make". */
 static Boolean
-ParseMaybeSubMake(const char *cmd)
+MaybeSubMake(const char *cmd)
 {
-    size_t i;
-    static struct {
-       const char *name;
-       size_t len;
-    } vals[] = {
-#define MKV(A) {       A, sizeof (A) - 1       }
-       MKV("${MAKE}"),
-       MKV("${.MAKE}"),
-       MKV("$(MAKE)"),
-       MKV("$(.MAKE)"),
-       MKV("make"),
-    };
-    for (i = 0; i < sizeof vals / sizeof vals[0]; i++) {
-       char *ptr;
-       if ((ptr = strstr(cmd, vals[i].name)) == NULL)
+    const char *start;
+
+    for (start = cmd; *start != '\0'; start++) {
+       const char *p = start;
+       char endc;
+
+       /* XXX: What if progname != "make"? */
+       if (p[0] == 'm' && p[1] == 'a' && p[2] == 'k' && p[3] == 'e')
+           if (start == cmd || !ch_isalnum(p[-1]))
+               if (!ch_isalnum(p[4]))
+                   return TRUE;
+
+       if (*p != '$')
            continue;
-       if ((ptr == cmd || !ch_isalnum(ptr[-1]))
-           && !ch_isalnum(ptr[vals[i].len]))
-           return TRUE;
+       p++;
+
+       if (*p == '{')
+           endc = '}';
+       else if (*p == '(')
+           endc = ')';
+       else
+           continue;
+       p++;
+
+       if (*p == '.')          /* Accept either ${.MAKE} or ${MAKE}. */
+           p++;
+
+       if (p[0] == 'M' && p[1] == 'A' && p[2] == 'K' && p[3] == 'E')
+           if (p[4] == endc)
+               return TRUE;
     }
     return FALSE;
 }
@@ -2079,7 +2084,7 @@
     /* if target already supplied, ignore commands */
     if (!(gn->type & OP_HAS_COMMANDS)) {
        Lst_Append(gn->commands, cmd);
-       if (ParseMaybeSubMake(cmd))
+       if (MaybeSubMake(cmd))
            gn->type |= OP_SUBMAKE;
        ParseMark(gn);
     } else {