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56 lines
1.5 KiB
56 lines
1.5 KiB
6 months ago
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From 08cbcd4dbc686bb38ec3093aff2f919fbff5ec17 Mon Sep 17 00:00:00 2001
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From: Noah Goldstein <goldstein.w.n@gmail.com>
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Date: Wed, 23 Jun 2021 19:19:34 -0400
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Subject: [PATCH] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S
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Content-type: text/plain; charset=UTF-8
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No bug. The way wcsnlen will check if near the end of maxlen
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is the following macro:
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mov %r11, %rsi; \
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subq %rax, %rsi; \
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andq $-64, %rax; \
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testq $-64, %rsi; \
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je L(strnlen_ret)
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Which words independently of s + maxlen overflowing. So the
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second overflow check is unnecissary for correctness and
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just extra overhead in the common no overflow case.
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test-strlen.c, test-wcslen.c, test-strnlen.c and test-wcsnlen.c are
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all passing
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Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
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Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
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---
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sysdeps/x86_64/multiarch/strlen-vec.S | 7 -------
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1 file changed, 7 deletions(-)
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diff --git a/sysdeps/x86_64/multiarch/strlen-vec.S b/sysdeps/x86_64/multiarch/strlen-vec.S
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index 439e486a..b7657282 100644
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--- a/sysdeps/x86_64/multiarch/strlen-vec.S
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+++ b/sysdeps/x86_64/multiarch/strlen-vec.S
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@@ -71,19 +71,12 @@ L(n_nonzero):
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suffice. */
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mov %RSI_LP, %R10_LP
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sar $62, %R10_LP
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- test %R10_LP, %R10_LP
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jnz __wcslen_sse4_1
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sal $2, %RSI_LP
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# endif
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-
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/* Initialize long lived registers. */
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-
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add %RDI_LP, %RSI_LP
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-# ifdef AS_WCSLEN
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-/* Check for overflow again from s + maxlen * sizeof(wchar_t). */
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- jbe __wcslen_sse4_1
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-# endif
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mov %RSI_LP, %R10_LP
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and $-64, %R10_LP
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mov %RSI_LP, %R11_LP
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--
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GitLab
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