[Bug rtl-optimization/65321] [5 Regression] ICE on valid code at -O2 and -O3 with -g enabled in decompose, at rtl.h:2007

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65321

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rsandifo at gcc dot gnu.org

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(gdb) p debug_rtx (x.first)
(const_int 128 [0x80])
(gdb) p x.second
$2 = QImode
(gdb) p precision 
$3 = 8

the CONST_INT is not properly sign-extended.  This is from

#6  0x0000000000d55381 in simplify_const_binary_operation (code=ASHIFT, 
    mode=QImode, op0=0x7ffff68d3490, op1=0x7ffff69e8b00)
    at /space/rguenther/src/svn/trunk2/gcc/simplify-rtx.c:4001
...
3997            case LSHIFTRT:
3998            case ASHIFTRT:
3999            case ASHIFT:
4000              {
4001                wide_int wop1 = pop1;
4002                if (SHIFT_COUNT_TRUNCATED)
4003                  wop1 = wi::umod_trunc (wop1, width);

but of course the shift amount need not be QImode as well.  128 is quite large,
but well...

Fact is that we don't know the mode of op1 here.  From the fact that the
const_int is not sign-extended we can conclude its mode is larger than QImode.
And we will truncate it anyway (or return NULL_RTX) if it is too large, so
it doesn't even matter.

I think we can simply use

              wide_int wop1 = std::make_pair (op1, MAX_MODE_INT);

here (or SImode maybe).  Or have a "don't care" way to make a wide-int
from a CONST_INT directly.

Richard?