forwprop: Recongize a store of integral zero for optimize_aggr_zeroprop.HEADtrunkmaster

While looking into the gimple level after optimization of the highway code
from google, I noticed in .optimized we still have:
```
  MEM <vector(8) short int> [(short int *)&a] = { 0, 0, 0, 0, 0, 0, 0, 0 };
  D.4398 = a;
  a ={v} {CLOBBER(eos)};
  D.4389 = D.4398;
  D.4390 = D.4389;
  D.4361 = D.4390;
  D.4195 = D.4361;
  return D.4195;
```
Note this is with SRA disabled since I noticed there is better code generation with
SRA disabled but that is a different story and I will get to that later on.

Which could be just optimized to a single store of `{}` .

The reason why the optimize_agr_copyprop does not handle the above is there was clobbers
inbetween the store in the last forwprop pass and currently don't copy after the first use.
While optimize_aggr_zeroprop does handle copying over clobbers just fine.

So this allows the recognization of the store to a to be like a memset to optimize_aggr_zeroprop
and then the result just falls through.

Bootstrapped and tested on x86_64-linux-gnu.

gcc/ChangeLog:

	* tree-ssa-forwprop.cc (optimize_aggr_zeroprop): Recognize stores
	of integer_zerop as memset of 0.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/copy-prop-aggr-zero-1.c: New test.
	* gcc.dg/torture/copy-prop-aggr-zero-2.c: New test.
	* gcc.dg/tree-ssa/copy-prop-aggregate-zero-1.c: New test.
	* gcc.dg/tree-ssa/copy-prop-aggregate-zero-2.c: New test.
	* gcc.dg/tree-ssa/copy-prop-aggregate-zero-3.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

0 files changed, 0 insertions, 0 deletions