From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Cree Subject: Alpha: suspicious compiler warning in entry.S Date: Wed, 28 Oct 2009 20:03:30 +1300 Message-ID: <4AE7ECC2.8050202@orcon.net.nz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Sender: linux-alpha-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-alpha@vger.kernel.org Cc: linux-kernel@vger.kernel.org, rth@twiddle.net, ink@jurassic.park.msu.ru, David Howells Compiler warning when compiling 2.6.32-rc5 as follows: AS arch/alpha/kernel/entry.o arch/alpha/kernel/entry.S: Assembler messages: arch/alpha/kernel/entry.S:326: Warning: operand out of range (0x0000000000000406 is not between 0x0000000000000000 and 0x00000000000000ff) arch/alpha/kernel/entry.S:388: Warning: operand out of range (0x0000000000000406 is not between 0x0000000000000000 and 0x00000000000000ff) One offending line (326) is: and $5, _TIF_WORK_MASK, $2 The warning occurs because commit d0420c83f39f "KEYS: Extend TIF_NOTIFY_RESUME to (almost) all architectures [try #6]" introduces TIF_NOTIFIY_RESUME which sets bit 10 in _TIF_WORK_MASK (see arch/alpha/include/asm/thread_info.h) but _TIF_WORK_MASK is used in the immediate addressing mode in the assembler instruction above. The 'and' instruction can only take an immediate datum in the range 0 to 255. With the addition of the TIF_NOTIFY_RESUME bit, _TIF_WORK_MASK is no longer in the valid range for immediate addressing in the 'and' instruction. On the assumption that it is important to include the TIF_NOTIFY_RESUME bit one might be tempted to modify the code to: lda $2, _TIF_WORK_MASK and $5, $2, $2 but this is time critical code. I am wondering whether it might be better to rearrange the bits in the thread information flags so that _TIF_WORK_MASK has a value less than 255 and the single instruction to perform an and operation can be maintained. Comments? Cheers Michael.