1 files changed, 6 insertions, 0 deletions
diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
index f43d581..32d63a9 100644
--- a/gcc/tree-ssa-threadedge.c
+++ b/gcc/tree-ssa-threadedge.c
@@ -265,6 +265,12 @@ record_temporary_equivalences_from_stmts_at_dest (edge e,
 	  && gimple_call_internal_unique_p (stmt))
 	return NULL;
 
+      /* We cannot thread through __builtin_constant_p, because an
+	 expression that is constant on two threading paths may become
+	 non-constant (i.e.: phi) when they merge.  */
+      if (gimple_call_builtin_p (stmt, BUILT_IN_CONSTANT_P))
+	return NULL;
+
       /* If duplicating this block is going to cause too much code
 	 expansion, then do not thread through this block.  */
       stmt_count++;