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commit 5542236837c5c41435f8282ec92799f480c36f18
Author: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue Jul 21 22:50:29 2015 -0700
Port the 0x7efe...feff pattern to GCC 6.
See Steve Ellcey's bug report in:
https://sourceware.org/ml/libc-alpha/2015-07/msg00673.html
* string/memrchr.c (MEMRCHR):
* string/rawmemchr.c (RAWMEMCHR):
* string/strchr.c (strchr):
* string/strchrnul.c (STRCHRNUL):
Rewrite code to avoid issues with signed shift overflow.
---
string/memrchr.c | 11 ++---------
string/rawmemchr.c | 11 ++---------
string/strchr.c | 9 ++-------
string/strchrnul.c | 9 ++-------
4 files changed, 8 insertions(+), 32 deletions(-)
--- a/string/memrchr.c
+++ b/string/memrchr.c
@@ -98,15 +98,8 @@
The 1-bits make sure that carries propagate to the next 0-bit.
The 0-bits provide holes for carries to fall into. */
-
- if (sizeof (longword) != 4 && sizeof (longword) != 8)
- abort ();
-
-#if LONG_MAX <= LONG_MAX_32_BITS
- magic_bits = 0x7efefeff;
-#else
- magic_bits = ((unsigned long int) 0x7efefefe << 32) | 0xfefefeff;
-#endif
+ magic_bits = -1;
+ magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
/* Set up a longword, each of whose bytes is C. */
charmask = c | (c << 8);
--- a/string/rawmemchr.c
+++ b/string/rawmemchr.c
@@ -90,15 +90,8 @@
The 1-bits make sure that carries propagate to the next 0-bit.
The 0-bits provide holes for carries to fall into. */
-
- if (sizeof (longword) != 4 && sizeof (longword) != 8)
- abort ();
-
-#if LONG_MAX <= LONG_MAX_32_BITS
- magic_bits = 0x7efefeff;
-#else
- magic_bits = ((unsigned long int) 0x7efefefe << 32) | 0xfefefeff;
-#endif
+ magic_bits = -1;
+ magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
/* Set up a longword, each of whose bytes is C. */
charmask = c | (c << 8);
--- a/string/strchr.c
+++ b/string/strchr.c
@@ -65,13 +65,8 @@
The 1-bits make sure that carries propagate to the next 0-bit.
The 0-bits provide holes for carries to fall into. */
- switch (sizeof (longword))
- {
- case 4: magic_bits = 0x7efefeffL; break;
- case 8: magic_bits = ((0x7efefefeL << 16) << 16) | 0xfefefeffL; break;
- default:
- abort ();
- }
+ magic_bits = -1;
+ magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
/* Set up a longword, each of whose bytes is C. */
charmask = c | (c << 8);
--- a/string/strchrnul.c
+++ b/string/strchrnul.c
@@ -63,13 +63,8 @@
The 1-bits make sure that carries propagate to the next 0-bit.
The 0-bits provide holes for carries to fall into. */
- switch (sizeof (longword))
- {
- case 4: magic_bits = 0x7efefeffL; break;
- case 8: magic_bits = ((0x7efefefeL << 16) << 16) | 0xfefefeffL; break;
- default:
- abort ();
- }
+ magic_bits = -1;
+ magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
/* Set up a longword, each of whose bytes is C. */
charmask = c | (c << 8);
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