re PR tree-optimization/82128 (ICE on valid code)

2017-09-13  Richard Biener  <rguenther@suse.de>

	PR middle-end/82128
	* gimple-fold.c (gimple_fold_call): Update SSA name in-place to
	default-def to avoid breaking iterator update with the weird
	interaction with cgraph_update_edges_for_call_stmt_node.

	* g++.dg/pr82128.C: New testcase.

From-SVN: r252062

gcc/ChangeLog

 2017-09-13  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/82128
+	* gimple-fold.c (gimple_fold_call): Update SSA name in-place to
+	default-def to avoid breaking iterator update with the weird
+	interaction with cgraph_update_edges_for_call_stmt_node.
+
+2017-09-13  Richard Biener  <rguenther@suse.de>
+
 	* tree-cfg.c (verify_gimple_assign_binary): Add verification
 	for WIDEN_SUM_EXPR, VEC_WIDEN_MULT_{HI,LO,EVEN,ODD}_EXPR,
 	VEC_PACK_{TRUNC,SAT,FIX_TRUNC}_EXPR.

gcc/gimple-fold.c

@@ -3862,24 +3862,18 @@ gimple_fold_call (gimple_stmt_iterator *gsi, bool inplace)
 		  tree fndecl = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
 		  gimple *new_stmt = gimple_build_call (fndecl, 0);
 		  gimple_set_location (new_stmt, gimple_location (stmt));
+		  /* If the call had a SSA name as lhs morph that into
+		     an uninitialized value.  */
 		  if (lhs && TREE_CODE (lhs) == SSA_NAME)
 		    {
 		      tree var = create_tmp_var (TREE_TYPE (lhs));
-		      tree def = get_or_create_ssa_default_def (cfun, var);
-
-		      /* To satisfy condition for
-			 cgraph_update_edges_for_call_stmt_node,
-			 we need to preserve GIMPLE_CALL statement
-			 at position of GSI iterator.  */
-		      update_call_from_tree (gsi, def);
-		      gsi_insert_before (gsi, new_stmt, GSI_NEW_STMT);
-		    }
-		  else
-		    {
-		      gimple_set_vuse (new_stmt, gimple_vuse (stmt));
-		      gimple_set_vdef (new_stmt, gimple_vdef (stmt));
-		      gsi_replace (gsi, new_stmt, false);
+		      SET_SSA_NAME_VAR_OR_IDENTIFIER (lhs, var);
+		      SSA_NAME_DEF_STMT (lhs) = gimple_build_nop ();
+		      set_ssa_default_def (cfun, var, lhs);
 		    }
+		  gimple_set_vuse (new_stmt, gimple_vuse (stmt));
+		  gimple_set_vdef (new_stmt, gimple_vdef (stmt));
+		  gsi_replace (gsi, new_stmt, false);
 		  return true;
 		}
 	    }

gcc/testsuite/ChangeLog

+2017-09-13  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/82128
+	* gimple-fold.c (gimple_fold_call): Update SSA name in-place to
+	default-def to avoid breaking iterator update with the weird
+	interaction with cgraph_update_edges_for_call_stmt_node.
+
 2017-09-13  Kugan Vivekanandarajah  <kuganv@linaro.org>
 
 	* gcc.target/aarch64/pr63304_1.c: Remove-mno-fix-cortex-a53-843419.

gcc/testsuite/g++.dg/pr82128.C

+// { dg-do compile }
+// { dg-options "-O3 -fno-tree-forwprop" }
+
+class A {
+      virtual unsigned long m_fn1() const;
+        virtual int &m_fn2(unsigned long) const;
+};
+class C : A {
+public:
+      int &m_fn2(unsigned long) const;
+        unsigned long m_fn1() const;
+};
+class B {
+      void m_fn3(const A &, const int &, const C &, int &) const;
+};
+void B::m_fn3(const A &, const int &, const C &, int &) const {
+      C &a(a);
+        for (long b = 0; a.m_fn1(); b++)
+	      a.m_fn2(0);
+}