On Thu, Nov 3, 2016 at 12:51 AM Uros Bizjak <ubiz...@gmail.com> wrote:
>
> Hello!
>
> > This patch adds a test to the cmpstrnsi pattern in i386.md so that it
> > will bail out (FAIL) if neither of the strings is a constant string. It
> > can only work as a proper strncmp if the length is not longer than both
> > of the strings. This change is required if expand_builtin_strncmp is
> > going to try expansion of strncmp when neither string argument is
> > constant.
>
> The patch needs a ChangeLog entry, but otherwise looks good.
I am checking in this patch to add a testcase for this condition.
--
H.J.
From 78170fb45ffc86a8c7fc18a662e3264045aced1b Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.to...@gmail.com>
Date: Sun, 17 May 2020 06:44:59 -0700
Subject: [PATCH] x86: Add gcc.target/i386/strncmp-1.c
Add a strncmp test for the cmpstrn pattern with neither of the strings
is a constant string. We can expand the cmpstrn pattern to "repz cmpsb"
only if one of the strings is a constant so that expand_builtin_strncmp()
can write the length argument to be the minimum of the const string
length and the actual length argument. Otherwise, "repz cmpsb" may pass
the 0 byte.
* gcc.target/i386/strncmp-1.c: New test.
---
gcc/testsuite/gcc.target/i386/strncmp-1.c | 47 +++++++++++++++++++++++
1 file changed, 47 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/i386/strncmp-1.c
diff --git a/gcc/testsuite/gcc.target/i386/strncmp-1.c b/gcc/testsuite/gcc.target/i386/strncmp-1.c
new file mode 100644
index 00000000000..044fc5cc5fa
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/strncmp-1.c
@@ -0,0 +1,47 @@
+/* { dg-do run { target mmap } } */
+/* { dg-options "-O2" } */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
+int
+__attribute__ ((noclone, noinline))
+compare (char *d, char *s, unsigned int l)
+{
+ return __builtin_strncmp (d, s, l);
+}
+
+int
+main ()
+{
+ size_t page_size = sysconf(_SC_PAGESIZE);
+ char *buf = mmap (0, 2 * page_size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (buf == MAP_FAILED)
+ {
+ perror ("mmap");
+ abort ();
+ }
+
+ if (mprotect (buf + page_size, page_size, PROT_NONE))
+ {
+ perror ("mprotect");
+ abort ();
+ }
+
+ char *src1 = buf + page_size - sizeof ("foo");
+ char *src2 = buf;
+ memcpy (src1, "foo", sizeof ("foo"));
+ memcpy (src2, "foo", sizeof ("foo"));
+ int result = compare (src1, src2, sizeof ("foo") + 16);
+ if (result != 0)
+ abort ();
+ return 0;
+}
--
2.26.2
