[Bug tree-optimization/61757] [4.10 Regression] genmodes failure with enable-checking

["pthaugen at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61757

--- Comment #19 from Pat Haugen <pthaugen at gcc dot gnu.org> ---
Tracked down the problem in 176.gcc to a difference in the generated code for
benchmark source toplev.c:exact_log2_wide(). Following compiled with -O3
-mcpu=power7.

int exact_log2_wide (unsigned int x)
{
  register int log = 0;

  if (x == 0 || x != (x & -x))
    return -1;
  while ((x >>= 1) != 0)
    log++;
  return log;
}

r212351:
    neg 9,3
    and 9,9,3
    cmplw 7,9,3
    bne 7,.L5
>>>	rldicl. 9,9,63,33
    li 3,0
    beq 0,.L6

r212352:
    neg 10,3
    and 10,10,3
    cmplw 7,10,3
    bne 7,.L5
>>>	srdi. 9,3,1
    li 3,0
    beq 0,.L6

r212351 is clearing the high word of the 64-bit register on the initial shift
right of 'x', whereas r212352 just starts shifting the whole 64-bit reg. The
reason this causes problems is that the callers are calling with an integer
arg:

#define exact_log2(N) exact_log2_wide ((HOST_WIDE_INT) (N))

So in the case where MIN_INT32 is passed (sign extended), the upper 32 bits are
'1' so r212352 returns a value of 63 whereas prior revisions returned a value
of 31.

Not sure if this is more of a benchmark source error, but figured I'd post my
findings in case it helps with the general problem.
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From: "emsr at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/57644] [C++1y] Cannot bind bitfield to lvalue reference
Date: Sat, 12 Jul 2014 01:42:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idW644

emsr at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |emsr at gcc dot gnu.org
         Resolution|---                         |FIXED

--- Comment #5 from emsr at gcc dot gnu.org ---
Fixed on trunk...