[PATCH] Fix PR C++/50970 -- Function pointer dereferenced twice in if statement on Arm cpu

[Zhenqiang Chen]

Hi,

PR 50970 is a general c++ front-end issue for targets which define
TARGET_PTRMEMFUNC_VBIT_LOCATION ptrmemfunc_vbit_in_delta, although the
reporter had issues only on ARM.

Root cause: It misses a check for side effects when generating pfn and
delta related expressions.

In the failed case, op0 is a function call. pfn0 and delta0 are
expressions based on the return value of op0. Without the check, the
function will be called twice.

The patch is to add the check for op0.

No make check regression on ARM.

Is it OK for trunk?

Thanks!
-Zhenqiang

cp/ChangeLog:
2012-09-20  Zhenqiang Chen <zhenqiang.c...@linaro.org>

        PR c++/50970
        * typeck.c (cp_build_binary_op): Check side effects before generating
        pfn and delta related expressions.

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index ad4b090..884f7d0 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -4159,18 +4159,23 @@ cp_build_binary_op (location_t location,
          if (TARGET_PTRMEMFUNC_VBIT_LOCATION
              == ptrmemfunc_vbit_in_delta)
            {
-             tree pfn0 = pfn_from_ptrmemfunc (op0);
-             tree delta0 = delta_from_ptrmemfunc (op0);
-             tree e1 = cp_build_binary_op (location,
-                                           EQ_EXPR,
-                                           pfn0,       
-                                           build_zero_cst (TREE_TYPE (pfn0)),
-                                           complain);
-             tree e2 = cp_build_binary_op (location,
-                                           BIT_AND_EXPR,
-                                           delta0,
-                                           integer_one_node,
-                                           complain);
+             tree pfn0, delta0, e1, e2;
+
+             if (TREE_SIDE_EFFECTS (op0))
+               op0 = save_expr (op0);
+
+             pfn0 = pfn_from_ptrmemfunc (op0);
+             delta0 = delta_from_ptrmemfunc (op0);
+             e1 = cp_build_binary_op (location,
+                                      EQ_EXPR,
+                                      pfn0,
+                                      build_zero_cst (TREE_TYPE (pfn0)),
+                                      complain);
+             e2 = cp_build_binary_op (location,
+                                      BIT_AND_EXPR,
+                                      delta0,
+                                      integer_one_node,
+                                      complain);
        
              if ((complain & tf_warning)
                  && c_inhibit_evaluation_warnings == 0