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To: gcc-patches@gcc.gnu.org
Subject: PR 71020: Handle abnormal PHIs in tree-call-cdce.c
From: Richard Sandiford <richard.sandiford@arm.com>
Gcc: private.sent
--text follows this line--
The PR is about a case where tree-call-cdce.c causes two abnormal
PHIs for the same variable to be live at the same time, leading to
a coalescing failure.  It seemed like getting rid of these kinds of
input would be generally useful, so I added a utility to tree-dfa.c.

Tested on x86_64-linux-gnu.

gcc/
	PR middle-end/71020
	* tree-dfa.h (replace_abnormal_ssa_names): Declare.
	* tree-dfa.c (replace_abnormal_ssa_names): New function.
	* tree-call-cdce.c: Include tree-dfa.h.
	(can_guard_call_p): New function, extracted from...
	(can_use_internal_fn): ...here.
	(shrink_wrap_one_built_in_call_with_conds): Remove failure path
	and return void.
	(shrink_wrap_one_built_in_call): Likewise.
	(use_internal_fn): Likewise.
	(shrink_wrap_conditional_dead_built_in_calls): Update accordingly
	and return void.  Call replace_abnormal_ssa_names.
	(pass_call_cdce::execute): Check can_guard_call_p during the
	initial walk.  Assume shrink_wrap_conditional_dead_built_in_calls
	will always change something.

gcc/testsuite/
	* gcc.dg/torture/pr71020.c: New test.

From-SVN: r236393

1 files changed, 23 insertions, 0 deletions

diff --git a/gcc/tree-dfa.c b/gcc/tree-dfa.c
index f6986c1..9a3b072 100644
--- a/gcc/tree-dfa.c
+++ b/gcc/tree-dfa.c
@@ -823,6 +823,29 @@ stmt_references_abnormal_ssa_name (gimple *stmt)
   return false;
 }
 
+/* If STMT takes any abnormal PHI values as input, replace them with
+   local copies.  */
+
+void
+replace_abnormal_ssa_names (gimple *stmt)
+{
+  ssa_op_iter oi;
+  use_operand_p use_p;
+
+  FOR_EACH_SSA_USE_OPERAND (use_p, stmt, oi, SSA_OP_USE)
+    {
+      tree op = USE_FROM_PTR (use_p);
+      if (TREE_CODE (op) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op))
+	{
+	  gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
+	  tree new_name = make_ssa_name (TREE_TYPE (op));
+	  gassign *assign = gimple_build_assign (new_name, op);
+	  gsi_insert_before (&gsi, assign, GSI_SAME_STMT);
+	  SET_USE (use_p, new_name);
+	}
+    }
+}
+
 /* Pair of tree and a sorting index, for dump_enumerated_decls.  */
 struct GTY(()) numbered_tree
 {