re PR target/38941 (CX isn't preserved with shift)

2009-01-27  H.J. Lu  <hongjiu.lu@intel.com>

	PR target/38941
	* doc/extend.texi: Improve local variable with asm reg.

From-SVN: r143719

gcc/ChangeLog

+2009-01-27  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/38941
+	* doc/extend.texi: Improve local variable with asm reg.
+
 2009-01-27  Adam Nemet  <anemet@caviumnetworks.com>
 
 	* c.opt (Wpacked-bitfield-compat): Change init value to -1.

gcc/doc/extend.texi

@@ -4852,6 +4852,8 @@ asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2));
 In the above example, beware that a register that is call-clobbered by
 the target ABI will be overwritten by any function call in the
 assignment, including library calls for arithmetic operators.
+Also a register may be clobbered when generating some operations,
+like variable shift, memory copy or memory move on x86.
 Assuming it is a call-clobbered register, this may happen to @code{r0}
 above by the assignment to @code{p2}.  If you have to use such a
 register, use temporary variables for expressions between the register