svn commit: r233684 - head/sys/x86/include

[Dimitry Andric]

Author: dim
Date: Thu Mar 29 23:31:48 2012
New Revision: 233684
URL: http://svn.freebsd.org/changeset/base/233684

Log:
  Fix an issue introduced in sys/x86/include/endian.h with r232721.  In
  that revision, the bswapXX_const() macros were renamed to bswapXX_gen().
  
  Also, bswap64_gen() was implemented as two calls to bswap32(), and
  similarly, bswap32_gen() as two calls to bswap16().  This mainly helps
  our base gcc to produce more efficient assembly.
  
  However, the arguments are not properly masked, which results in the
  wrong value being calculated in some instances.  For example,
  bswap32(0x12345678) returns 0x7c563412, and bswap64(0x123456789abcdef0)
  returns 0xfcdefc9a7c563412.
  
  Fix this by appropriately masking the arguments to bswap16() in
  bswap32_gen(), and to bswap32() in bswap64_gen().  This should also
  silence warnings from clang.
  
  Submitted by:	jh

Modified:
  head/sys/x86/include/endian.h

Modified: head/sys/x86/include/endian.h
==============================================================================
--- head/sys/x86/include/endian.h	Thu Mar 29 23:30:17 2012	(r233683)
+++ head/sys/x86/include/endian.h	Thu Mar 29 23:31:48 2012	(r233684)
@@ -65,9 +65,9 @@
 
 #define	__bswap16_gen(x)	(__uint16_t)((x) << 8 | (x) >> 8)
 #define	__bswap32_gen(x)		\
-	(((__uint32_t)__bswap16(x) << 16) | __bswap16((x) >> 16))
+	(((__uint32_t)__bswap16((x) & 0xffff) << 16) | __bswap16((x) >> 16))
 #define	__bswap64_gen(x)		\
-	(((__uint64_t)__bswap32(x) << 32) | __bswap32((x) >> 32))
+	(((__uint64_t)__bswap32((x) & 0xffffffff) << 32) | __bswap32((x) >> 32))
 
 #ifdef __GNUCLIKE_BUILTIN_CONSTANT_P
 #define	__bswap16(x)				\