[Bug middle-end/56420] [4.8 Regression] Arithmetic error in computation with compile time unsigned __int128 constant

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56420



--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-02-21 
21:29:33 UTC ---

Author: jakub

Date: Thu Feb 21 21:29:29 2013

New Revision: 196215



URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=196215

Log:

    PR middle-end/56420

    * expmed.c (EXACT_POWER_OF_2_OR_ZERO_P): Do subtraction in uhwi, to

    avoid signed wrapping.

    (expand_mult): Handle properly multiplication by

    ((dword_type) -1) << (BITS_PER_WORD - 1).  Improve multiplication by

    ((dword_type) 1) << (BITS_PER_WORD - 1).  Avoid undefined behavior

    in the compiler if coeff is HOST_WIDE_INT_MIN.

    (expand_divmod): Don't make ext_op1 static, change it's type to

    uhwi.  Avoid undefined behavior in -INTVAL (op1).



    * gcc.dg/torture/pr56420.c: New test.



Added:

    trunk/gcc/testsuite/gcc.dg/torture/pr56420.c

Modified:

    trunk/gcc/ChangeLog

    trunk/gcc/expmed.c

    trunk/gcc/testsuite/ChangeLog