From: Noah Goldstein <goldstein.w.n@gmail.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH] x86-64: Use notl in EVEX strcmp [BZ #28646]
Date: Fri, 3 Dec 2021 21:50:04 -0600 [thread overview]
Message-ID: <CAFUsyf+RtS2zeoTiF85jh2wd4cWbERoB6g3zWhedzwMtTBZ3nw@mail.gmail.com> (raw)
In-Reply-To: <20211204032420.3158-1-hjl.tools@gmail.com>
On Fri, Dec 3, 2021 at 9:24 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> From: Noah Goldstein <goldstein.w.n@gmail.com>
>
> Must use notl %edi here as lower bits are for CHAR comparisons
> potentially out of range thus can be 0 without indicating mismatch.
> This fixes BZ #28646.
>
> Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>
> ---
> string/test-strcmp.c | 28 ++++++++++++++++++++++++++
> sysdeps/x86_64/multiarch/strcmp-evex.S | 14 +++++++------
> 2 files changed, 36 insertions(+), 6 deletions(-)
>
> diff --git a/string/test-strcmp.c b/string/test-strcmp.c
> index 77ae73110f..42178a260b 100644
> --- a/string/test-strcmp.c
> +++ b/string/test-strcmp.c
> @@ -23,6 +23,7 @@
> # define TEST_NAME "strcmp"
> #endif
> #include "test-string.h"
> +#include <support/test-driver.h>
>
> #ifdef WIDE
> # include <wchar.h>
> @@ -390,6 +391,32 @@ check2 (void)
> }
> }
>
> +static void
> +check3 (void)
> +{
> + size_t size = 0xd000 + 0x4000;
> + CHAR *s1, *s2;
> + CHAR *buffer1 = mmap (NULL, size, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANON, -1, 0);
> + CHAR *buffer2 = mmap (NULL, size, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANON, -1, 0);
> + if (buffer1 == MAP_FAILED || buffer1 == MAP_FAILED)
> + error (EXIT_UNSUPPORTED, errno, "mmap failed");
> +
> + s1 = (CHAR *) (buffer1 + 0x8f8 / sizeof (CHAR));
> + s2 = (CHAR *) (buffer2 + 0xcff3 / sizeof (CHAR));
> +
> + STRCPY(s1, L("/export/redhat/rpms/BUILD/java-1.8.0-openjdk-1.8.0.312.b07-2.fc35.x86_64/openjdk/langtools/src/share/classes/com/sun/tools/doclets/internal/toolkit/util/PathDocFileFactory.java"));
> + STRCPY(s2, L("/export/redhat/rpms/BUILD/java-1.8.0-openjdk-1.8.0.312.b07-2.fc35.x86_64/openjdk/langtools/src/share/classes/com/sun/tools/doclets/internal/toolkit/taglets/ThrowsTaglet.java"));
> +
> + int exp_result = SIMPLE_STRCMP (s1, s2);
> + FOR_EACH_IMPL (impl, 0)
> + check_result (impl, s1, s2, exp_result);
> +
> + munmap ((void *) buffer1, size);
> + munmap ((void *) buffer2, size);
> +}
> +
> int
> test_main (void)
> {
> @@ -398,6 +425,7 @@ test_main (void)
> test_init ();
> check();
> check2 ();
> + check3 ();
>
> printf ("%23s", "");
> FOR_EACH_IMPL (impl, 0)
> diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> index 0bea318abd..b68e1f7a1e 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> @@ -646,12 +646,13 @@ L(loop_cross_page):
> in YMM3 and 32 bytes at VEC_SIZE(%rdx, %r10). */
> VPCMP $0, VEC_SIZE(%rdx, %r10), %YMM3, %k3{%k4}
> kmovd %k3, %edi
> + /* Must use notl %edi here as lower bits are for CHAR
> + comparisons potentially out of range thus can be 0 without
> + indicating mismatch. */
> + notl %edi
> # ifdef USE_AS_WCSCMP
> /* Don't use subl since it is the upper 8 bits of EDI below. */
> - notl %edi
> andl $0xff, %edi
> -# else
> - incl %edi
> # endif
>
> # ifdef USE_AS_WCSCMP
> @@ -733,12 +734,13 @@ L(loop_cross_page_2_vec):
> in YMM1 and 32 bytes at (VEC_SIZE * 3)(%rdx, %r10). */
> VPCMP $0, (VEC_SIZE * 3)(%rdx, %r10), %YMM1, %k3{%k4}
> kmovd %k3, %edi
> + /* Must use notl %edi here as lower bits are for CHAR
> + comparisons potentially out of range thus can be 0 without
> + indicating mismatch. */
> + notl %edi
> # ifdef USE_AS_WCSCMP
> /* Don't use subl since it is the upper 8 bits of EDI below. */
> - notl %edi
> andl $0xff, %edi
> -# else
> - incl %edi
> # endif
>
> # ifdef USE_AS_WCSCMP
> --
> 2.33.1
>
LGTM
next prev parent reply other threads:[~2021-12-04 3:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-04 3:24 H.J. Lu
2021-12-04 3:50 ` Noah Goldstein [this message]
2022-04-23 1:49 ` Sunil Pandey
2021-12-04 8:14 ` Andreas Schwab
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