tree d2011cf8167adb8939c5d464958cbac9fe46ec4e
parent 17e8fef1af2db3a13613a311db2ec2f7a69645a1
author Richard Sandiford <rdsandiford@googlemail.com> 1358710254 +0000
committer Aurelien Jarno <aurelien@aurel32.net> 1359672052 +0100

target-mips: Sign-extend the result of LWR

Sign-extend the result of LWR, as is already done for LWL.  This is necessary
in the case where LWR loads the full word (i.e. the address is actually
aligned).  In the other cases, it is implementation defined whether the
upper 32 bits of the result are unchanged or a copy of bit 31.  The latter
seems easier to implement.

Previously the code used:

    (oldval & (0xfffffffe << (31 - bitshift))) | (newval >> bitshift)

which zeroed the upper bits of the register, losing any previous sign
extension in the unaligned cases.

Signed-off-by: Richard Sandiford <rdsandiford@googlemail.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>