[gcc r12-7381] Copy EH phi args for throwing hardened compares

[gcc r12-7381] Copy EH phi args for throwing hardened compares

[Alexandre Oliva]

https://gcc.gnu.org/g:e53bb1965db9c7882ded4a70296340d8db52053a

commit r12-7381-ge53bb1965db9c7882ded4a70296340d8db52053a
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Thu Feb 24 22:03:32 2022 -0300

    Copy EH phi args for throwing hardened compares
    
    When we duplicate a throwing compare for hardening, the EH edge from
    the original compare gets duplicated for the inverted compare, but we
    failed to adjust any PHI nodes in the EH block.  This patch adds the
    needed adjustment, copying the PHI args from those of the preexisting
    edge.
    
    
    for  gcc/ChangeLog
    
            PR tree-optimization/103856
            * gimple-harden-conditionals.cc (non_eh_succ_edge): Enable the
            eh edge to be requested through an extra parameter.
            (pass_harden_compares::execute): Copy PHI args in the EH dest
            block for the new EH edge added for the inverted compare.
    
    for  gcc/testsuite/ChangeLog
    
            PR tree-optimization/103856
            * g++.dg/pr103856.C: New.

Diff:
---
 gcc/gimple-harden-conditionals.cc | 31 ++++++++++++++++++++++++++++---
 gcc/testsuite/g++.dg/pr103856.C   | 17 +++++++++++++++++
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/gcc/gimple-harden-conditionals.cc b/gcc/gimple-harden-conditionals.cc
index 9418194cb20..6a5fc3fb9e1 100644
--- a/gcc/gimple-harden-conditionals.cc
+++ b/gcc/gimple-harden-conditionals.cc
@@ -361,9 +361,9 @@ make_pass_harden_conditional_branches (gcc::context *ctxt)
 }
 
 /* Return the fallthru edge of a block whose other edge is an EH
-   edge.  */
+   edge.  If EHP is not NULL, store the EH edge in it.  */
 static inline edge
-non_eh_succ_edge (basic_block bb)
+non_eh_succ_edge (basic_block bb, edge *ehp = NULL)
 {
   gcc_checking_assert (EDGE_COUNT (bb->succs) == 2);
 
@@ -375,6 +375,9 @@ non_eh_succ_edge (basic_block bb)
   gcc_checking_assert (!(ret->flags & EDGE_EH)
 		       && (eh->flags & EDGE_EH));
 
+  if (ehp)
+    *ehp = eh;
+
   return ret;
 }
 
@@ -538,8 +541,9 @@ pass_harden_compares::execute (function *fun)
 	    add_stmt_to_eh_lp (asgnck, lookup_stmt_eh_lp (asgn));
 	    make_eh_edges (asgnck);
 
+	    edge ckeh;
 	    basic_block nbb = split_edge (non_eh_succ_edge
-					  (gimple_bb (asgnck)));
+					  (gimple_bb (asgnck), &ckeh));
 	    gsi_split = gsi_start_bb (nbb);
 
 	    if (dump_file)
@@ -547,6 +551,27 @@ pass_harden_compares::execute (function *fun)
 		       "Splitting non-EH edge from block %i into %i after"
 		       " the newly-inserted reversed throwing compare\n",
 		       gimple_bb (asgnck)->index, nbb->index);
+
+	    if (!gimple_seq_empty_p (phi_nodes (ckeh->dest)))
+	      {
+		edge aseh;
+		non_eh_succ_edge (gimple_bb (asgn), &aseh);
+
+		gcc_checking_assert (aseh->dest == ckeh->dest);
+
+		for (gphi_iterator psi = gsi_start_phis (ckeh->dest);
+		     !gsi_end_p (psi); gsi_next (&psi))
+		  {
+		    gphi *phi = psi.phi ();
+		    add_phi_arg (phi, PHI_ARG_DEF_FROM_EDGE (phi, aseh), ckeh,
+				 gimple_phi_arg_location_from_edge (phi, aseh));
+		  }
+
+		if (dump_file)
+		  fprintf (dump_file,
+			   "Copying PHI args in EH block %i from %i to %i\n",
+			   aseh->dest->index, aseh->src->index, ckeh->src->index);
+	      }
 	  }
 
 	gcc_checking_assert (single_succ_p (gsi_bb (gsi_split)));
diff --git a/gcc/testsuite/g++.dg/pr103856.C b/gcc/testsuite/g++.dg/pr103856.C
new file mode 100644
index 00000000000..26c7d875025
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr103856.C
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-Og -fnon-call-exceptions -fsignaling-nans -fharden-compares" } */
+
+struct S {
+  S(float);
+  S();
+  operator float();
+  ~S() {}
+};
+
+int
+main() {
+  S s_arr[] = {2};
+  S var1;
+  if (var1)
+    ;
+}