Hi!
On the following testcase, VN during free keeps iterating forever, since
the unshare_expr call I've added to fix PR55935. The bug is that
when we have
volatile int a[1];
and &a[0] expression, if we unshare_expr that expression, it doesn't compare
operand_equal_p (exp, unshare_expr (exp), OEP_PURE_SAME). While when
looking at ADDR_EXPR we set OEP_CONSTANT_ADDRESS_OF flag, when
looking at the ARRAY_REF we see it has TREE_SIDE_EFFECTS set and return 0.
For ADDR_EXPR of ARRAY_REF or other reference it really doesn't matter
whether the ARRAY_REF itself has side-effects or not though, so we should
ignore the side-effects.
Fixed thusly, bootstrapped/regtested on x86_64-linux, ok for trunk?
2013-02-26 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/56448
* fold-const.c (operand_equal_p) <case tcc_reference>: Don't look at
TREE_SIDE_EFFECTS if flags contain OEP_CONSTANT_ADDRESS_OF.
Clear OEP_CONSTANT_ADDRESS_OF from flags before recursing on second or
later operands of the references, or even first operand for
INDIRECT_REF, TARGET_MEM_REF or MEM_REF.
* gcc.c-torture/compile/pr56448.c: New test.
--- gcc/fold-const.c.jj 2013-02-08 16:05:34.000000000 +0100
+++ gcc/fold-const.c 2013-02-25 23:25:46.676092462 +0100
@@ -2542,19 +2542,25 @@ operand_equal_p (const_tree arg0, const_
case tcc_reference:
/* If either of the pointer (or reference) expressions we are
- dereferencing contain a side effect, these cannot be equal. */
- if (TREE_SIDE_EFFECTS (arg0)
- || TREE_SIDE_EFFECTS (arg1))
+ dereferencing contain a side effect, these cannot be equal,
+ but their addresses can be. */
+ if ((flags & OEP_CONSTANT_ADDRESS_OF) == 0
+ && (TREE_SIDE_EFFECTS (arg0)
+ || TREE_SIDE_EFFECTS (arg1)))
return 0;
switch (TREE_CODE (arg0))
{
case INDIRECT_REF:
+ flags &= ~OEP_CONSTANT_ADDRESS_OF;
+ return OP_SAME (0);
+
case REALPART_EXPR:
case IMAGPART_EXPR:
return OP_SAME (0);
case TARGET_MEM_REF:
+ flags &= ~OEP_CONSTANT_ADDRESS_OF;
/* Require equal extra operands and then fall through to MEM_REF
handling of the two common operands. */
if (!OP_SAME_WITH_NULL (2)
@@ -2563,6 +2569,7 @@ operand_equal_p (const_tree arg0, const_
return 0;
/* Fallthru. */
case MEM_REF:
+ flags &= ~OEP_CONSTANT_ADDRESS_OF;
/* Require equal access sizes, and similar pointer types.
We can have incomplete types for array references of
variable-sized arrays from the Fortran frontent
@@ -2581,22 +2588,28 @@ operand_equal_p (const_tree arg0, const_
/* Operands 2 and 3 may be null.
Compare the array index by value if it is constant first as we
may have different types but same value here. */
- return (OP_SAME (0)
- && (tree_int_cst_equal (TREE_OPERAND (arg0, 1),
- TREE_OPERAND (arg1, 1))
- || OP_SAME (1))
+ if (!OP_SAME (0))
+ return 0;
+ flags &= ~OEP_CONSTANT_ADDRESS_OF;
+ return ((tree_int_cst_equal (TREE_OPERAND (arg0, 1),
+ TREE_OPERAND (arg1, 1))
+ || OP_SAME (1))
&& OP_SAME_WITH_NULL (2)
&& OP_SAME_WITH_NULL (3));
case COMPONENT_REF:
/* Handle operand 2 the same as for ARRAY_REF. Operand 0
may be NULL when we're called to compare MEM_EXPRs. */
- return OP_SAME_WITH_NULL (0)
- && OP_SAME (1)
- && OP_SAME_WITH_NULL (2);
+ if (!OP_SAME_WITH_NULL (0))
+ return 0;
+ flags &= ~OEP_CONSTANT_ADDRESS_OF;
+ return OP_SAME (1) && OP_SAME_WITH_NULL (2);
case BIT_FIELD_REF:
- return OP_SAME (0) && OP_SAME (1) && OP_SAME (2);
+ if (!OP_SAME (0))
+ return 0;
+ flags &= ~OEP_CONSTANT_ADDRESS_OF;
+ return OP_SAME (1) && OP_SAME (2);
default:
return 0;
--- gcc/testsuite/gcc.c-torture/compile/pr56448.c.jj 2013-02-25
23:31:55.266922056 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr56448.c 2013-02-25
23:29:55.000000000 +0100
@@ -0,0 +1,14 @@
+/* PR tree-optimization/56448 */
+
+volatile int a[1];
+int b;
+
+void
+foo ()
+{
+ for (;;)
+ {
+ int *c[3][6] = { 0, 0, 0, &b, 0, 0, 0, 0, &b, 0, 0, 0, 0, 0, 0, 0, &b,
(int *) &a[0] };
+ b = *c[2][5];
+ }
+}
Jakub
