[Bug rtl-optimization/78588] rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is too large for 64-bit type 'long unsigned int'

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78588

--- Comment #1 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Author: trippels
Date: Wed Nov 30 07:30:55 2016
New Revision: 242997

URL: https://gcc.gnu.org/viewcvs?rev=242997&root=gcc&view=rev
Log:
Fix PR78588 - rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is
too large for 64-bit type

Building gcc with -fsanitize=undefined shows:
 rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is too large for
64-bit type 'long unsigned int'

This happens because if_then_else_cond() in combine.c calls
num_sign_bit_copies() in rtlanal.c with mode==BLKmode.

5205   bitwidth = GET_MODE_PRECISION (mode);
5206   if (bitwidth > HOST_BITS_PER_WIDE_INT)
5207     return 1;
5208
5209   nonzero = nonzero_bits (x, mode);
5210   return nonzero & (HOST_WIDE_INT_1U << (bitwidth - 1))
5211          ? 1 : bitwidth - floor_log2 (nonzero) - 1;

This causes (bitwidth - 1) to wrap around.

        PR rtl-optimization/78588
        * combine.c (if_then_else_cond): Also guard against BLKmode.
        * rtlanal.c (num_sign_bit_copies1): Add assert.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/combine.c
    trunk/gcc/rtlanal.c