https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101858
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |12.0
Component|c |middle-end
Status|NEW |ASSIGNED
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
#0 build2 (code=RSHIFT_EXPR, tt=<pointer_type 0x7ffff65649d8>,
arg0=<convert_expr 0x7ffff6686260>, arg1=<parm_decl 0x7ffff669d000 a>)
at /home/rguenther/src/gcc2/gcc/tree.c:4970
#1 0x0000000000eb1bab in fold_binary_loc (loc=2147483651, code=LT_EXPR,
type=<integer_type 0x7ffff655c5e8 int>, op0=<convert_expr 0x7ffff6686260>,
op1=<convert_expr 0x7ffff6686220>)
at /home/rguenther/src/gcc2/gcc/fold-const.c:12510
/* Similarly for X < (cast) (1 << Y). But cast can't be narrowing,
otherwise Y might be >= # of bits in X's type and thus e.g.
(unsigned char) (1 << Y) for Y 15 might be 0.
If the cast is widening, then 1 << Y should have unsigned type,
otherwise if Y is number of bits in the signed shift type minus 1,
we can't optimize this. E.g. (unsigned long long) (1 << Y) for Y
31 might be 0xffffffff80000000. */
if ((code == LT_EXPR || code == GE_EXPR)
&& TYPE_UNSIGNED (TREE_TYPE (arg0))
&& CONVERT_EXPR_P (arg1)
&& TREE_CODE (TREE_OPERAND (arg1, 0)) == LSHIFT_EXPR
&& (element_precision (TREE_TYPE (arg1))
>= element_precision (TREE_TYPE (TREE_OPERAND (arg1, 0))))
&& (TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (arg1, 0)))
|| (element_precision (TREE_TYPE (arg1))
== element_precision (TREE_TYPE (TREE_OPERAND (arg1, 0)))))
&& integer_onep (TREE_OPERAND (TREE_OPERAND (arg1, 0), 0)))
{
tem = build2 (RSHIFT_EXPR, TREE_TYPE (arg0), arg0,
TREE_OPERAND (TREE_OPERAND (arg1, 0), 1));
return build2_loc (loc, code == LT_EXPR ? EQ_EXPR : NE_EXPR, type,
fold_convert_loc (loc, TREE_TYPE (arg0), tem),
build_zero_cst (TREE_TYPE (arg0)));
}
Mine.
