Re: [PATCH] Don't add REG_EQUAL notes in fwprop for paradoxical subregs (PR rtl-optimization/70574)

[Bernd Schmidt <bschmidt at redhat dot com>]

On 04/08/2016 07:05 PM, Jakub Jelinek wrote:
> After IRC discussions, I've bootstrapped/regtested following patch that
> just punts if *loc contains any paradoxical subregs, together with
> additional statistics gathering that proved that the new testcase is
> the only spot in which this patch makes a difference on x86_64-linux
> and i686-linux bootstrap/regtest.
>
> Of course on other targets it might affect more.

I ran the test with just not generating any REG_EQUAL notes here in 
fwprop, and out of 4492 source files only three showed code generation 
differences, which suggests we're not getting much value out of these.

Two of the cases where the same missed tree optimization, for which I've 
filed PR70600.

> 2016-04-08  Jakub Jelinek  <jakub@redhat.com>
>
> 	PR rtl-optimization/70574
> 	* fwprop.c (forward_propagate_and_simplify): Don't add
> 	REG_EQUAL note if DF_REF_REG (use) is a paradoxical subreg.
> 	(try_fwprop_subst): Don't add REG_EQUAL note if there are any
> 	paradoxical subregs within *loc.
>
> 	* gcc.target/i386/avx2-pr70574.c: New test.

Ok.


Bernd