Hi!
As described in the PR, this is an attempt to avoid false positive
-Warray-bounds warnings by adding some extra ASSERT_EXPRs in vrp,
so that it can better optimize the code.
For
if (x >> cst1 == cst2)
we can assert that (x - ((unsigned) cst2 << cst1) < (1U << cst1))
and e.g. for
if (x >> cst1 >= cst2)
we can assert that (x >= (cst2 << cst1)).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2012-01-02 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/51721
* tree-vrp.c (register_edge_assert_for_2): If comparing
lhs of right shift by constant with an integer constant,
add ASSERT_EXPRs for the rhs1 of the right shift.
* gcc.dg/tree-ssa/vrp63.c: New test.
* gcc.dg/pr51721.c: New test.
--- gcc/tree-vrp.c.jj 2011-12-02 01:52:27.000000000 +0100
+++ gcc/tree-vrp.c 2012-01-02 09:33:08.676635403 +0100
@@ -4464,6 +4464,93 @@ register_edge_assert_for_2 (tree name, e
}
}
+ /* Similarly add asserts for NAME == CST and NAME being defined as
+ NAME = NAME2 >> CST2. */
+ if (TREE_CODE_CLASS (comp_code) == tcc_comparison
+ && TREE_CODE (val) == INTEGER_CST)
+ {
+ gimple def_stmt = SSA_NAME_DEF_STMT (name);
+ tree name2 = NULL_TREE, cst2 = NULL_TREE;
+ tree val2 = NULL_TREE;
+ unsigned HOST_WIDE_INT mask[2] = { 0, 0 };
+
+ /* Extract CST2 from the right shift. */
+ if (is_gimple_assign (def_stmt)
+ && gimple_assign_rhs_code (def_stmt) == RSHIFT_EXPR)
+ {
+ name2 = gimple_assign_rhs1 (def_stmt);
+ cst2 = gimple_assign_rhs2 (def_stmt);
+ if (TREE_CODE (name2) == SSA_NAME
+ && host_integerp (cst2, 1)
+ && (unsigned HOST_WIDE_INT) tree_low_cst (cst2, 1)
+ < 2 * HOST_BITS_PER_WIDE_INT
+ && INTEGRAL_TYPE_P (TREE_TYPE (name2))
+ && live_on_edge (e, name2)
+ && !has_single_use (name2))
+ {
+ if ((unsigned HOST_WIDE_INT) tree_low_cst (cst2, 1)
+ < HOST_BITS_PER_WIDE_INT)
+ mask[0] = ((unsigned HOST_WIDE_INT) 1
+ << tree_low_cst (cst2, 1)) - 1;
+ else
+ {
+ mask[1] = ((unsigned HOST_WIDE_INT) 1
+ << (tree_low_cst (cst2, 1)
+ - HOST_BITS_PER_WIDE_INT)) - 1;
+ mask[0] = -1;
+ }
+ val2 = fold_binary (LSHIFT_EXPR, TREE_TYPE (val), val, cst2);
+ }
+ }
+
+ if (val2 != NULL_TREE
+ && TREE_CODE (val2) == INTEGER_CST
+ && simple_cst_equal (fold_build2 (RSHIFT_EXPR,
+ TREE_TYPE (val),
+ val2, cst2), val))
+ {
+ enum tree_code new_comp_code = comp_code;
+ tree tmp, new_val;
+
+ tmp = name2;
+ if (comp_code == EQ_EXPR || comp_code == NE_EXPR)
+ {
+ if (!TYPE_UNSIGNED (TREE_TYPE (val)))
+ {
+ unsigned int prec = TYPE_PRECISION (TREE_TYPE (val));
+ tree type = build_nonstandard_integer_type (prec, 1);
+ tmp = build1 (NOP_EXPR, type, name2);
+ val2 = fold_convert (type, val2);
+ }
+ tmp = fold_build2 (MINUS_EXPR, TREE_TYPE (tmp), tmp, val2);
+ new_val = build_int_cst_wide (TREE_TYPE (tmp), mask[0], mask[1]);
+ new_comp_code = comp_code == EQ_EXPR ? LE_EXPR : GT_EXPR;
+ }
+ else if (comp_code == LT_EXPR || comp_code == GE_EXPR)
+ new_val = val2;
+ else
+ {
+ new_val = build_int_cst_wide (TREE_TYPE (val2),
+ mask[0], mask[1]);
+ new_val = fold_binary (BIT_IOR_EXPR, TREE_TYPE (val2),
+ val2, new_val);
+ }
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "Adding assert for ");
+ print_generic_expr (dump_file, name2, 0);
+ fprintf (dump_file, " from ");
+ print_generic_expr (dump_file, tmp, 0);
+ fprintf (dump_file, "\n");
+ }
+
+ register_new_assert_for (name2, tmp, new_comp_code, new_val,
+ NULL, e, bsi);
+ retval = true;
+ }
+ }
+
return retval;
}
--- gcc/testsuite/gcc.dg/tree-ssa/vrp63.c.jj 2012-01-02 10:47:57.972533062
+0100
+++ gcc/testsuite/gcc.dg/tree-ssa/vrp63.c 2012-01-02 10:47:27.000000000
+0100
@@ -0,0 +1,345 @@
+/* PR tree-optimization/51721 */
+/* { dg-do link } */
+/* { dg-options "-O2" } */
+
+extern void link_error (void);
+
+#define BITSM1 (sizeof (int) * __CHAR_BIT__ - 1)
+
+void
+f1 (unsigned int s)
+{
+ if (s >> 1 == 0)
+ {
+ if (s == 2 || s == -1U)
+ link_error ();
+ }
+ else
+ {
+ if (s == 0 || s == 1)
+ link_error ();
+ }
+}
+
+void
+f2 (unsigned int s)
+{
+ if (s >> 4 != 3)
+ {
+ if (s == 48 || s == 57 || s == 63)
+ link_error ();
+ }
+ else
+ {
+ if (s == 47 || s == 64 || s == 0 || s == -1U)
+ link_error ();
+ }
+}
+
+void
+f3 (int s)
+{
+ if (s >> 3 == -2)
+ {
+ if (s == -17 || s == -8 || s == 0
+ || s == -__INT_MAX__ - 1 || s == __INT_MAX__)
+ link_error ();
+ }
+ else
+ {
+ if (s == -16 || s == -12 || s == -9)
+ link_error ();
+ }
+}
+
+void
+f4 (unsigned int s)
+{
+ if (s >> 2 < 4)
+ {
+ if (s == 16 || s == 20 || s == -1U)
+ link_error ();
+ }
+ else
+ {
+ if (s == 0 || s == 2 || s == 14 || s == 15)
+ link_error ();
+ }
+}
+
+void
+f5 (unsigned int s)
+{
+ if (s >> 3 <= 7)
+ {
+ if (s == 64 || s == 68 || s == -1U)
+ link_error ();
+ }
+ else
+ {
+ if (s == 0 || s == 1 || s == 62 || s == 63)
+ link_error ();
+ }
+}
+
+void
+f6 (unsigned int s)
+{
+ if (s >> 1 > 2)
+ {
+ if (s == 0 || s == 3 || s == 5)
+ link_error ();
+ }
+ else
+ {
+ if (s == 6 || s == 8 || s == -1U)
+ link_error ();
+ }
+}
+
+void
+f7 (unsigned int s)
+{
+ if (s >> 5 >= 7)
+ {
+ if (s == 0 || s == 2 || s == 221 || s == 223)
+ link_error ();
+ }
+ else
+ {
+ if (s == 224 || s == 256 || s == 258 || s == -1U)
+ link_error ();
+ }
+}
+
+void
+f8 (int s)
+{
+ if (s >> 2 < -3)
+ {
+ if (s == -12 || s == -10 || s == 0 || s == __INT_MAX__)
+ link_error ();
+ }
+ else
+ {
+ if (s == -13 || s == -16 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+}
+
+void
+f9 (int s)
+{
+ if (s >> 3 <= -2)
+ {
+ if (s == -8 || s == -6 || s == 0 || s == __INT_MAX__)
+ link_error ();
+ }
+ else
+ {
+ if (s == -9 || s == -11 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+}
+
+void
+f10 (int s)
+{
+ if (s >> 1 > -4)
+ {
+ if (s == -7 || s == -9 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+ else
+ {
+ if (s == -6 || s == -4 || s == 0 || s == __INT_MAX__)
+ link_error ();
+ }
+}
+
+void
+f11 (int s)
+{
+ if (s >> 3 >= -6)
+ {
+ if (s == -49 || s == -51 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+ else
+ {
+ if (s == -48 || s == -46 || s == 0 || s == __INT_MAX__)
+ link_error ();
+ }
+}
+
+void
+f12 (int s)
+{
+ if (s >> 2 < 4)
+ {
+ if (s == 16 || s == 20 || s == __INT_MAX__)
+ link_error ();
+ }
+ else
+ {
+ if (s == 0 || s == 2 || s == 14 || s == 15
+ || s == -2 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+}
+
+void
+f13 (int s)
+{
+ if (s >> 3 <= 7)
+ {
+ if (s == 64 || s == 68 || s == __INT_MAX__)
+ link_error ();
+ }
+ else
+ {
+ if (s == 0 || s == 1 || s == 62 || s == 63
+ || s == -2 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+}
+
+void
+f14 (int s)
+{
+ if (s >> 1 > 2)
+ {
+ if (s == 0 || s == 3 || s == 5
+ || s == -2 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+ else
+ {
+ if (s == 6 || s == 8 || s == __INT_MAX__)
+ link_error ();
+ }
+}
+
+void
+f15 (int s)
+{
+ if (s >> 5 >= 7)
+ {
+ if (s == 0 || s == 2 || s == 221 || s == 223
+ || s == -2 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+ else
+ {
+ if (s == 224 || s == 256 || s == 258 || s == __INT_MAX__)
+ link_error ();
+ }
+}
+
+unsigned int
+f16 (unsigned int s)
+{
+ unsigned int t = s >> BITSM1;
+ if (t != 0)
+ {
+ if (s == 0 || s == 5 || s == __INT_MAX__)
+ link_error ();
+ }
+ else
+ {
+ if (s == 1U + __INT_MAX__ || s == 6U + __INT_MAX__ || s == -1U)
+ link_error ();
+ }
+ return t;
+}
+
+int
+f17 (int s)
+{
+ int t = s >> BITSM1;
+ if (t == 0)
+ {
+ if (s == -1 || s == -5 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+ else
+ {
+ if (s == 0 || s == 5 || s == __INT_MAX__)
+ link_error ();
+ }
+ return t;
+}
+
+unsigned int
+f18 (unsigned int s)
+{
+ unsigned int t = s >> BITSM1;
+ if (t >= 1)
+ {
+ if (s == 0 || s == 5 || s == __INT_MAX__)
+ link_error ();
+ }
+ else
+ {
+ if (s == 1U + __INT_MAX__ || s == 6U + __INT_MAX__ || s == -1U)
+ link_error ();
+ }
+ return t;
+}
+
+int
+f19 (int s)
+{
+ int t = s >> BITSM1;
+ if (t >= 0)
+ {
+ if (s == -1 || s == -5 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+ else
+ {
+ if (s == 0 || s == 5 || s == __INT_MAX__)
+ link_error ();
+ }
+ return t;
+}
+
+unsigned int
+f20 (unsigned int s)
+{
+ unsigned int t = s >> BITSM1;
+ if (t < 1)
+ {
+ if (s == 1U + __INT_MAX__ || s == 6U + __INT_MAX__ || s == -1U)
+ link_error ();
+ }
+ else
+ {
+ if (s == 0 || s == 5 || s == __INT_MAX__)
+ link_error ();
+ }
+ return t;
+}
+
+int
+f21 (int s)
+{
+ int t = s >> BITSM1;
+ if (t < 0)
+ {
+ if (s == 0 || s == 5 || s == __INT_MAX__)
+ link_error ();
+ }
+ else
+ {
+ if (s == -1 || s == -5 || s == -__INT_MAX__ - 1)
+ link_error ();
+ }
+ return t;
+}
+
+int
+main ()
+{
+ return 0;
+}
--- gcc/testsuite/gcc.dg/pr51721.c.jj 2012-01-02 09:35:51.621616998 +0100
+++ gcc/testsuite/gcc.dg/pr51721.c 2012-01-02 09:35:39.000000000 +0100
@@ -0,0 +1,31 @@
+/* PR tree-optimization/51721 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -Warray-bounds" } */
+
+static int a[10], b[10], c[10], d[10];
+
+unsigned int
+f (unsigned int v)
+{
+ return v == 17 ? 11 : v;
+}
+
+unsigned int
+g (unsigned int v)
+{
+ return v == 17 ? 17 : v;
+}
+
+void
+t (unsigned int s)
+{
+ if (s >> 1 == 0)
+ {
+ a[f (s)] = 0; /* { dg-bogus "array subscript is above array bounds" }
*/
+ a[f (s)] = 0; /* { dg-bogus "array subscript is above array bounds" }
*/
+ b[f (s)] = 0; /* { dg-bogus "array subscript is above array bounds" }
*/
+ c[g (s)] = 0; /* { dg-bogus "array subscript is above array bounds" }
*/
+ c[g (s)] = 0; /* { dg-bogus "array subscript is above array bounds" }
*/
+ d[f (s)] = 0; /* { dg-bogus "array subscript is above array bounds" }
*/
+ }
+}
Jakub
