On Fri, Mar 31, 2017 at 2:57 PM, Bin.Cheng <amker.ch...@gmail.com> wrote:
> On Fri, Mar 31, 2017 at 11:37 AM, Richard Biener <rguent...@suse.de> wrote:
>> On Fri, 31 Mar 2017, Markus Trippelsdorf wrote:
>>
>>> On 2017.03.31 at 11:16 +0200, Richard Biener wrote:
>>> > On Fri, 31 Mar 2017, Richard Biener wrote:
>>> >
>>> > > On Fri, 31 Mar 2017, Rainer Orth wrote:
>>> > >
>>> > > > Hi Christophe,
>>> > > >
>>> > > > > With this patch, the following testcase now fails on arm* targets:
>>> > > > > gcc.dg/tree-ssa/pr71347.c scan-tree-dump-not optimized ".* = MEM.*;"
>>> > > >
>>> > > > same on Solaris/SPARC.
>>> > >
>>> > > I've reverted r241968 with (patch reverted). It doesn't include
>>> > > sparc, so please amend as you see fit.
>>> >
>>> > Ah, r241441. I'll fixup myself then.
>>>
>>> It also fails on some X86 configurations:
>>> https://gcc.gnu.org/ml/gcc-regression/2017-03/msg00237.html
>>> https://gcc.gnu.org/ml/gcc-regression/2017-03/msg00238.html
>>
>> I see. The test is somewhat strange (well, it's an IVOPTS test). To
>> simulate the effect of the PRE changes we could simply enable
>> -fpredictive-commoning on it.
>>
>> Let's ask Bin what the testcase was supposed to test... (the testcase
>> comment suggests that pcom is applied but it certainly wasn't before
>> the xfails were removed).
>
> It's supposed to test that both loads inside loop can be optimized,
> X[i-1] by predcom or pre; X[1] by loop invariant. When the test is
> added, neither pre nor predcom (not at O2) can do this, but we have
> another chance that pre + ivopts + dom together can eliminate X[i-1].
> But this really depends on each pass does the right thing. That's
> also why it is added with ivopts change. Back in time, it was ivopts
> did "wrong". Apparently, having a test on different passes is
> fragile. I will send a patch adding option "-fpredictive-commoning"
> because predcom seems the right pass to do that. Also given we are
> considering enabling predcom at O2 for GCC 8.
Here is the patch. Test result checked on arm-none-eabi. Is it OK?
Thanks,
bin
gcc/testsuite/ChangeLog
2017-03-31 Bin Cheng <bin.ch...@arm.com>
* gcc.dg/tree-ssa/pr71347.c: Add predcom and drop XFAIL.
Thanks,
bin
Index: gcc/testsuite/gcc.dg/tree-ssa/pr71347.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/pr71347.c (revision 246615)
+++ gcc/testsuite/gcc.dg/tree-ssa/pr71347.c (working copy)
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-options "-O2 -fdump-tree-optimized -fpredictive-commoning" } */
double in;
extern void Write (double);
@@ -14,4 +14,4 @@
}
/* Load of X[i - i] can be omitted by reusing X[i] in previous iteration. */
-/* { dg-final { scan-tree-dump-not ".* = MEM.*;" "optimized" { xfail {
ia64-*-* arm*-*-* m68k*-*-* sparc*-*-* } } } } */
+/* { dg-final { scan-tree-dump-not ".* = MEM.*;" "optimized" } } */
