2012/1/11 Richard Guenther <[email protected]>:
>
> count despite being declared volatile and only loaded once in the source
> is loaded twice in gimple. If it were a HW register which destroys the
> device after the 2nd load without an intervening store you'd wrecked
> the device ;)
>
> Richard.
Thanks for explaination. I tried to flip order for lhs/rhs in
gimplify_modify_expr & co. Issue here is that for some cases we are
relying here on lhs for gimplifying rhs (is_gimple_reg_rhs_or_call vs
is_gimple_mem_rhs_or_call) and this doesn't work for cases in C++
like:
typedef const unsigned char _Jv_Utf8Const;
typedef __SIZE_TYPE__ uaddr;
void maybe_adjust_signature (_Jv_Utf8Const *&s, uaddr &special)
{
union {
_Jv_Utf8Const *signature;
uaddr signature_bits;
};
signature = s;
special = signature_bits & 1;
signature_bits -= special;
s = signature;
}
So I modified gimplify_self_mod_expr for post-inc/dec so that we use
following sequence
and add it to pre_p for it:
tmp = lhs;
lvalue = tmp (+/-) rhs
*expr_p = tmp;
ChangeLog
2012-02-08 Kai Tietz <[email protected]>
PR middle-end/48814
* gimplify.c (gimplify_self_mod_expr): Move for
postfix-inc/dec the modification in pre and return
temporary with origin value.
2012-02-08 Kai Tietz <[email protected]>
* gcc.c-torture/execute/pr48814-1.c: New test.
* gcc.c-torture/execute/pr48814-2.c: New test.
* gcc.dg/tree-ssa/assign-1.c: New test.
* gcc.dg/tree-ssa/assign-2.c: New test.
I did boostrap for all languages (including Ada and Obj-C++) and
regression tests on host x86_64-unknown-linux-gnu. Ok for apply?
Regards,
Kai
Index: gcc/gcc/gimplify.c
===================================================================
--- gcc.orig/gcc/gimplify.c
+++ gcc/gcc/gimplify.c
@@ -2197,7 +2197,7 @@ gimplify_self_mod_expr (tree *expr_p, gi
bool want_value)
{
enum tree_code code;
- tree lhs, lvalue, rhs, t1;
+ tree lhs, lvalue, rhs, t1, t2;
gimple_seq post = NULL, *orig_post_p = post_p;
bool postfix;
enum tree_code arith_code;
@@ -2264,20 +2264,23 @@ gimplify_self_mod_expr (tree *expr_p, gi
arith_code = POINTER_PLUS_EXPR;
}
- t1 = build2 (arith_code, TREE_TYPE (*expr_p), lhs, rhs);
-
- if (postfix)
- {
- gimplify_assign (lvalue, t1, orig_post_p);
- gimplify_seq_add_seq (orig_post_p, post);
- *expr_p = lhs;
- return GS_ALL_DONE;
- }
- else
+ if (!postfix)
{
+ t1 = build2 (arith_code, TREE_TYPE (*expr_p), lhs, rhs);
*expr_p = build2 (MODIFY_EXPR, TREE_TYPE (lvalue), lvalue, t1);
return GS_OK;
}
+
+ /* Assign lhs to temporary variable. */
+ t2 = create_tmp_var (TREE_TYPE (lhs), NULL);
+ gimplify_assign (t2, lhs, pre_p);
+ /* Do increment and assign it to lvalue. */
+ t1 = build2 (arith_code, TREE_TYPE (*expr_p), t2, rhs);
+ gimplify_assign (lvalue, t1, pre_p);
+
+ gimplify_seq_add_seq (orig_post_p, post);
+ *expr_p = t2;
+ return GS_ALL_DONE;
}
/* If *EXPR_P has a variable sized type, wrap it in a WITH_SIZE_EXPR. */
Index: gcc/gcc/testsuite/gcc.c-torture/execute/pr48814-1.c
===================================================================
--- /dev/null
+++ gcc/gcc/testsuite/gcc.c-torture/execute/pr48814-1.c
@@ -0,0 +1,18 @@
+extern void abort (void);
+
+int arr[] = {1,2,3,4};
+int count = 0;
+
+int __attribute__((noinline))
+incr (void)
+{
+ return ++count;
+}
+
+int main()
+{
+ arr[count++] = incr ();
+ if (count != 2 || arr[count] != 3)
+ abort ();
+ return 0;
+}
Index: gcc/gcc/testsuite/gcc.c-torture/execute/pr48814-2.c
===================================================================
--- /dev/null
+++ gcc/gcc/testsuite/gcc.c-torture/execute/pr48814-2.c
@@ -0,0 +1,18 @@
+extern void abort (void);
+
+int arr[] = {1,2,3,4};
+int count = 0;
+
+int
+incr (void)
+{
+ return ++count;
+}
+
+int main()
+{
+ arr[count++] = incr ();
+ if (count != 2 || arr[count] != 3)
+ abort ();
+ return 0;
+}
Index: gcc/gcc/testsuite/gcc.dg/tree-ssa/assign-1.c
===================================================================
--- /dev/null
+++ gcc/gcc/testsuite/gcc.dg/tree-ssa/assign-1.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+volatile int count;
+void bar(int);
+void foo()
+{
+ bar(count++);
+}
+
+/* { dg-final { scan-tree-dump-times "count =" 1 "optimized"} } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/gcc/testsuite/gcc.dg/tree-ssa/assign-2.c
===================================================================
--- /dev/null
+++ gcc/gcc/testsuite/gcc.dg/tree-ssa/assign-2.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+volatile int count;
+int arr[4];
+void foo()
+{
+ arr[count++] = 0;
+}
+
+/* { dg-final { scan-tree-dump-times "count =" 1 "optimized"} } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
+
