From e53bb1965db9c7882ded4a70296340d8db52053a Mon Sep 17 00:00:00 2001
From: Alexandre Oliva <oliva@adacore.com>
Date: Thu, 24 Feb 2022 22:03:32 -0300
Subject: [PATCH] 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.
---
 gcc/gimple-harden-conditionals.cc | 31 ++++++++++++++++++++++++++++---
 gcc/testsuite/g++.dg/pr103856.C   | 17 +++++++++++++++++
 2 files changed, 45 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/pr103856.C

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)
+    ;
+}