Patch ping (Re: [PATCH] Fix x86 bzhi/bextr iff zero_extract with zero size is undefined (PR rtl-optimization/87817))

[Jakub Jelinek]

Hi!

On Wed, Nov 14, 2018 at 12:37:02AM +0100, Jakub Jelinek wrote:
> 2018-11-13  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR rtl-optimization/87817
> 	* config/i386/i386.md (nmi2_bzhi_<mode>3, *bmi2_bzhi_<mode>3,
> 	*bmi2_bzhi_<mode>3_1, *bmi2_bzhi_<mode>3_1_ccz): Use IF_THEN_ELSE
> 	in the pattern to avoid triggering UB when operands[2] is zero.
> 	(tbm_bextri_<mode>): New expander.  Renamed the old define_insn to ...
> 	(*tbm_bextri_<mode>): ... this.

I'd like to ping this patch, while the folding committed for the PR
often triggers and so the RTL passes see literal zero propagated there less
often, e.g. the testcase with:
-O2 -mbmi2 -fno-tree-ccp -fno-tree-forwprop -fno-tree-fre -fno-tree-pre -fno-tree-vrp -fno-tree-dominator-opts -fno-code-hoisting
is still miscompiled and there could be other reasons why a zero appears
only after expansion.

>From what I understood, the agreement was that zero_extract with 0 size
(either literal or just at runtime is incorrect in the middle-end).

	Jakub