[PATCH] PR69195, Reload confused by invalid reg equivs

[Richard Biener]

On March 12, 2016 10:29:40 AM GMT+01:00, Jakub Jelinek <jakub@redhat.com> wrote:
>On Sat, Mar 12, 2016 at 07:37:25PM +1030, Alan Modra wrote:
>> > I believe Alan's point is DSE deleted the assignment to x which
>can't be
>> > right as long as we've left in goto *&x.
>> > 
>> > The goto *&x should be a use of x and thus should have kept the
>assignment
>> > live.
>> 
>> Right, I wasn't trying to say that ira.c:indirect_jump_optimize is
>> OK.  It needs the patch I posted or perhaps even better a test of
>> DF_REF_INSN_INFO rather than !DF_REF_IS_ARTIFICIAL (simply because
>the
>> flag test is reading another field, and we need to read
>> DF_REF_INSN_INFO anyway).
>
>Ok, that was my point.  BTW, DSE isn't the only one that deletes x = 0;
>cddce deletes it too.  -fno-tree-dse -fno-tree-dce preserves it till
>expansion.

GIMPLE_GOTO doesn't have VOPs and I don't think that we'd want VUSEs on all gotos. But just having them on indirect gotos would be inconsistent.

I believe the code is undefined anyway and out of scope of a reasonable QOI.

Using alloca to create/jump to code on the stack should work (we might transform that into a decl though).

Richard.

>	Jakub