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authorFlorian Weimer <fweimer@redhat.com>2017-06-23 17:23:44 +0200
committerFlorian Weimer <fweimer@redhat.com>2017-06-23 17:24:40 +0200
commit3ec7c02cc3e922b9364dc8cfd1d4546671b91003 (patch)
tree283d54448fe89359272093156316884e61992c9a /string
parent7fa1d9462baabc5a1058efc13a48444af4678acf (diff)
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x86-64: memcmp-avx2-movbe.S needs saturating subtraction [BZ #21662]
This code: L(between_2_3): /* Load as big endian with overlapping loads and bswap to avoid branches. */ movzwl -2(%rdi, %rdx), %eax movzwl -2(%rsi, %rdx), %ecx shll $16, %eax shll $16, %ecx movzwl (%rdi), %edi movzwl (%rsi), %esi orl %edi, %eax orl %esi, %ecx bswap %eax bswap %ecx subl %ecx, %eax ret needs a saturating subtract because the full register is used. With this commit, only the lower 24 bits of the register are used, so a regular subtraction suffices. The test case change adds coverage for these kinds of bugs.
Diffstat (limited to 'string')
-rw-r--r--string/test-memcmp.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/string/test-memcmp.c b/string/test-memcmp.c
index a7969edaea0..15389305348 100644
--- a/string/test-memcmp.c
+++ b/string/test-memcmp.c
@@ -441,11 +441,12 @@ check1 (void)
n = 116;
for (size_t i = 0; i < n; i++)
- {
- exp_result = SIMPLE_MEMCMP (s1 + i, s2 + i, n - i);
- FOR_EACH_IMPL (impl, 0)
- check_result (impl, s1 + i, s2 + i, n - i, exp_result);
- }
+ for (size_t len = 0; len <= n - i; ++len)
+ {
+ exp_result = SIMPLE_MEMCMP (s1 + i, s2 + i, len);
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, s1 + i, s2 + i, len, exp_result);
+ }
}
/* This test checks that memcmp doesn't overrun buffers. */