https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98178
--- Comment #1 from Uroš Bizjak <ubizjak at gmail dot com> ---
The attached patch with the following testcase:
--cut here--
int test (int a, int b)
{
return a << (b & 31);
}
--cut here--
fails to generate a single shift insn, because it does not trigger the call to
combine_split_insns. The reason is the following condition:
/* If we were combining three insns and the result is a simple SET
with no ASM_OPERANDS that wasn't recognized, try to split it into two
insns. There are two ways to do this. It can be split using a
machine-specific method (like when you have an addition of a large
constant) or by combine in the function find_split_point. */
if (i1 && insn_code_number < 0 && GET_CODE (newpat) == SET
&& asm_noperands (newpat) < 0)
where i1 is null.
Please note, that omitting FLAGS_REG is intentional, c.f. PR96226#c2.
