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

[Richard Biener via Gcc-patches]

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, OK?

Thanks,
Richard.

        PR tree-optimization/110434
        * tree-nrv.cc (pass_nrv::execute): Remove CLOBBERs of
        VAR we replace with <retval>.
---
 gcc/tree-nrv.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/gcc/tree-nrv.cc b/gcc/tree-nrv.cc
index ff47439647c..466b491e4e7 100644
--- a/gcc/tree-nrv.cc
+++ b/gcc/tree-nrv.cc
@@ -256,6 +256,14 @@ pass_nrv::execute (function *fun)
              gsi_remove (&gsi, true);
              release_defs (stmt);
            }
+         /* If this is a CLOBBER of VAR, remove it.  */
+         else if (gimple_clobber_p (stmt)
+                  && gimple_assign_lhs (stmt) == found)
+           {
+             unlink_stmt_vdef (stmt);
+             gsi_remove (&gsi, true);
+             release_defs (stmt);
+           }
          else
            {
              struct walk_stmt_info wi;
-- 
2.35.3