On Fri, Jan 13, 2017 at 4:58 PM, Uros Bizjak <ubiz...@gmail.com> wrote:
> On Fri, Jan 13, 2017 at 12:50 PM, Alan Modra <amo...@gmail.com> wrote:
>> Rather than using unspecs in doloop insns to stop combine creating
>> these insns, use legitimate_combined_insn.
>>
>> I'm not sure why the original patch implementing
>> legitimate_combined_insn did not store the result of recog to the insn
>> but it seems good to me, and would allow the recog call in
>> ix86_legitimate_combined_insn to be omitted. (I tested that too, not
>> shown here.)
>
> IIRC, I copied operand scanning loop from recog.c (around line 2580)
> and the function was later enhanced with preferred alternatives
> handling. The function worked well, and not being an expert in this
> area, I didn't try to "optimize" the code that worked...
>
> So, there is no particular reason for the current implementation.
FYI, the following patch immediately crashed build:
--cut here--
Index: i386.c
===================================================================
--- i386.c (revision 244463)
+++ i386.c (working copy)
@@ -8130,7 +8130,7 @@ ix86_legitimate_combined_insn (rtx_insn *insn)
generating insn patterns with invalid hard register operands.
These invalid insns can eventually confuse reload to error out
with a spill failure. See also PRs 46829 and 46843. */
- if ((INSN_CODE (insn) = recog (PATTERN (insn), insn, 0)) >= 0)
+ if (INSN_CODE (insn) >= 0)
{
int i;
--cut here--
/home/uros/gcc-svn/trunk/libgcc/libgcc2.c:557:1: internal compiler
error: Segmentation fault
}
^
0xe82bcc crash_signal
/home/uros/gcc-svn/trunk/gcc/toplev.c:333
0x1621444 insn_extract(rtx_insn*)
/ssd/uros/gcc-build/gcc/insn-extract.c:7453
0xd9e345 extract_insn(rtx_insn*)
/home/uros/gcc-svn/trunk/gcc/recog.c:2317
0x126e662 ix86_legitimate_combined_insn
/home/uros/gcc-svn/trunk/gcc/config/i386/i386.c:8137
0x1814568 recog_for_combine_1
/home/uros/gcc-svn/trunk/gcc/combine.c:11206
0x1814d73 recog_for_combine
/home/uros/gcc-svn/trunk/gcc/combine.c:11363
0x17ffb69 try_combine
/home/uros/gcc-svn/trunk/gcc/combine.c:3824
0x17f8d7e combine_instructions
/home/uros/gcc-svn/trunk/gcc/combine.c:1372
0x181cb67 rest_of_handle_combine
/home/uros/gcc-svn/trunk/gcc/combine.c:14607
0x181cc28 execute
/home/uros/gcc-svn/trunk/gcc/combine.c:14652
It looks that recog_for_combine doesn't do everything recog does.
Uros.
