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From: Shu-Chun Weng <scw@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/grte_v5] More aggressively prevent a buffer from being optimized out Date: Thu, 15 Jul 2021 19:41:05 +0000 (GMT) [thread overview] Message-ID: <20210715194105.986E3385DC15@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=7903140dcc2b36c4eadae7132fb51a4463fd134e commit 7903140dcc2b36c4eadae7132fb51a4463fd134e Author: Shu-Chun Weng <scw@google.com> Date: Mon May 3 16:12:44 2021 -0700 More aggressively prevent a buffer from being optimized out The volatile global variable was first introduced in e86f9654c. I have noticed the compiler still optimizing the buffer out on AArch64 presumably because the assignment is after all other observable behaviors so it's still valid to eliminate it. Diff: --- string/tst-xbzero-opt.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/string/tst-xbzero-opt.c b/string/tst-xbzero-opt.c index e9c411b2ef..4f16c4d678 100644 --- a/string/tst-xbzero-opt.c +++ b/string/tst-xbzero-opt.c @@ -119,17 +119,17 @@ static void setup_no_clear (void) { unsigned char buf[TEST_BUFFER_SIZE]; - prepare_test_buffer (buf); vol_glob = buf; + prepare_test_buffer (buf); } static void setup_ordinary_clear (void) { unsigned char buf[TEST_BUFFER_SIZE]; + vol_glob = buf; prepare_test_buffer (buf); memset (buf, 0, TEST_BUFFER_SIZE); - vol_glob = buf; } static void
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