On 12/01/2016 04:21 AM, Paolo Bonzini wrote:
In code like the following from KVM:

        /* it is a read fault? */
        error_code = (exit_qualification << 2) & PFERR_FETCH_MASK;

it would be nicer to write

        /* it is a read fault? */
        error_code = (exit_qualification & VMX_EPT_READ_FAULT_MASK) ? 

instead of having to know the difference between the positions of the
source and destination bits.  LLVM catches the latter just fine (which
is why I am sending this in stage 3...), but GCC does not, so this
patch adds two patterns to catch it.

The combine.c hunk of v1 has been committed already.

Bootstrapped/regtested x86_64-pc-linux-gnu, ok?


2016-11-26  Paolo Bonzini  <bonz...@gnu.org>

        * match.pd: Simplify X ? C : 0 where C is a power of 2 and
        X tests a single bit.

2016-11-26  Paolo Bonzini  <bonz...@gnu.org>

        * gcc.dg/fold-and-lshift.c, gcc.dg/fold-and-rshift-1.c,
        gcc.dg/fold-and-rshift-2.c: New testcases.

Reply via email to