[PATCH][vs] tree-optimization/110434 - avoid <retval> ={v} {CLOBBER} from NRV

[PATCH][vs] tree-optimization/110434 - avoid <retval> ={v} {CLOBBER} from NRV

[Richard Biener]

When NRV replaces a local variable with <retval> it also replaces
occurences in clobbers.  This leads to <retval> being clobbered
before the return of it which is strictly invalid but harmless in
practice since there's no pass after NRV which would remove
earlier stores.

The following fixes this nevertheless.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

	PR tree-optimization/110434
	* tree-nrv.cc (pass_nrv::execute): Remove CLOBBERs of
	VAR we replace with <retval>.
---
 gcc/tree-nrv.cc | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-nrv.cc b/gcc/tree-nrv.cc
index ff47439647c..99c4e21a842 100644
--- a/gcc/tree-nrv.cc
+++ b/gcc/tree-nrv.cc
@@ -264,7 +264,17 @@ pass_nrv::execute (function *fun)
 	      data.modified = 0;
 	      walk_gimple_op (stmt, finalize_nrv_r, &wi);
 	      if (data.modified)
-		update_stmt (stmt);
+		{
+		  /* If this is a CLOBBER of VAR, remove it.  */
+		  if (gimple_clobber_p (stmt))
+		    {
+		      unlink_stmt_vdef (stmt);
+		      gsi_remove (&gsi, true);
+		      release_defs (stmt);
+		      continue;
+		    }
+		  update_stmt (stmt);
+		}
 	      gsi_next (&gsi);
 	    }
 	}
-- 
2.35.3