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Re: [PATCH] Fix PR69771, bogus CONST_INT during shift expansion


On February 15, 2016 4:34:38 PM GMT+01:00, Jakub Jelinek <jakub@redhat.com> wrote:
>On Sat, Feb 13, 2016 at 07:50:25AM +0000, James Greenhalgh wrote:
>> On Fri, Feb 12, 2016 at 05:34:21PM +0100, Jakub Jelinek wrote:
>> > On Fri, Feb 12, 2016 at 03:20:07PM +0100, Bernd Schmidt wrote:
>> > > >>-  mode1 = GET_MODE (xop1) != VOIDmode ? GET_MODE (xop1) :
>mode;
>> > > >>+  mode1 = GET_MODE (xop1) != VOIDmode ? GET_MODE (xop1) :
>mode1;
>> > > >>    if (xmode1 != VOIDmode && xmode1 != mode1)
>> > > >>      {
>> > > 
>> > > Here, things aren't so clear, and the fact that the mode1
>calculation now
>> > > differs from the mode0 one may be overlooked by someone in the
>future.
>> > > 
>> > > Rather than use codes like "mode variable is VOIDmode", I'd
>prefer to use
>> > > booleans with descriptive names, like "op1_may_need_conversion".
>> > 
>> > So do you prefer e.g. following?  Bootstrapped/regtested on
>x86_64-linux and
>> > i686-linux.
>> > 
>> > 2016-02-12  Jakub Jelinek  <jakub@redhat.com>
>> > 
>> > 	PR rtl-optimization/69764
>> > 	PR rtl-optimization/69771
>> > 	* optabs.c (expand_binop_directly): For shift_optab_p, force
>> > 	convert_modes with VOIDmode if xop1 has VOIDmode.
>> > 
>> > 	* c-c++-common/pr69764.c: New test.
>> > 	* gcc.dg/torture/pr69771.c: New testcase.
>> > 
>> 
>> These two new tests are failing for me on AArch64 as so:
>
>As I said earlier, I wanted to fix it in expand_binop_directly because
>the
>higher levels still GEN_INT the various shift counters and then call
>expand_binop_directly.  But, as can be seen on aarch64/arm/m68k, there
>are
>cases that need op1 to be valid for mode already in expand_binop, so in
>addition to the already committed fix I think we need to handle it
>at the expand_binop level too.
>As we don't have a single spot with convert_modes like
>expand_binop_directly, I think the best is to do there a change
>for the uncommon and invalid cases only, like (seems to fix the ICE
>both on aarch64 and m68k):

We could also force_reg those at expansion or apply SHIFT_COUNT_TRUNCATED to those invalid constants there.

Richard.

>2016-02-15  Jakub Jelinek  <jakub@redhat.com>
>
>	PR rtl-optimization/69764
>	PR rtl-optimization/69771
>	* optabs.c (expand_binop): Ensure for shift optabs invalid CONST_INT
>	op1 is valid for mode.
>
>--- gcc/optabs.c.jj	2016-02-12 17:49:25.000000000 +0100
>+++ gcc/optabs.c	2016-02-15 16:15:53.983673792 +0100
>@@ -1125,6 +1125,12 @@ expand_binop (machine_mode mode, optab b
>       op1 = negate_rtx (mode, op1);
>       binoptab = add_optab;
>     }
>+  /* For shifts, constant invalid op1 might be expanded from different
>+     mode than MODE.  */
>+  else if (CONST_INT_P (op1)
>+	   && shift_optab_p (binoptab)
>+	   && UINTVAL (op1) >= GET_MODE_BITSIZE (GET_MODE_INNER (mode)))
>+    op1 = gen_int_mode (INTVAL (op1), mode);
> 
>   /* Record where to delete back to if we backtrack.  */
>   last = get_last_insn ();
>
>
>	Jakub



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