On Tue, 25 Mar 2014, Jakub Jelinek wrote:
> On Tue, Mar 25, 2014 at 10:15:37AM +0100, Richard Biener wrote:
> > On Tue, 25 Mar 2014, Richard Biener wrote:
> >
> > > On Tue, 25 Mar 2014, Jakub Jelinek wrote:
> > >
> > > > Hi!
> > > >
> > > > While working on previous patch, I've noticed a severe omission in the
> > > > -fsanitize=signed-integer-overflow support. Nothing ever
> > > > folds addition/subtraction of 0 and multiplication by [0,1], none of
> > > > these
> > > > may ever overflow and thus we can fold them to normal operations and let
> > > > those be folded as normal operations.
> > > >
> > > > Bootstrapped/regtested on x86_64-linux and i686-linux, tested with
> > > > --with-build-config=bootstrap-ubsan bootstrap on i686-linux, ok for
> > > > trunk?
> > >
> > > I think you only need to adjust gimple_fold_stmt_to_constant_1.
> >
> > Actually there only for a * 0 and a - a, as others don't result in
> > constants. Still the other cases should be handled in fold_stmt,
> > not only in VRP.
>
> Ok, here is an updated patch that optimizes this in VRP,
> gimple_fold_stmt_to_constant_1 and gimple_fold_call.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok.
Thanks,
Richard.
> 2014-03-25 Jakub Jelinek <ja...@redhat.com>
>
> * tree-vrp.c (simplify_internal_call_using_ranges): If only
> one range is range_int_cst_p, but not both, at least optimize
> addition/subtraction of 0 and multiplication by 0 or 1.
> * gimple-fold.c (gimple_fold_call): Fold
> IFN_UBSAN_CHECK_{ADD,SUB,MUL}.
> (gimple_fold_stmt_to_constant_1): If both op0 and op1 aren't
> INTEGER_CSTs, try to fold at least x * 0 and y - y.
>
> --- gcc/tree-vrp.c.jj 2014-03-25 09:22:01.352151925 +0100
> +++ gcc/tree-vrp.c 2014-03-25 11:25:44.898562545 +0100
> @@ -9336,31 +9336,58 @@ simplify_internal_call_using_ranges (gim
> else if (TREE_CODE (op0) == INTEGER_CST)
> set_value_range_to_value (&vr0, op0, NULL);
> else
> - return false;
> + set_value_range_to_varying (&vr0);
>
> if (TREE_CODE (op1) == SSA_NAME)
> vr1 = *get_value_range (op1);
> else if (TREE_CODE (op1) == INTEGER_CST)
> set_value_range_to_value (&vr1, op1, NULL);
> else
> - return false;
> + set_value_range_to_varying (&vr1);
>
> - if (!range_int_cst_p (&vr0) || !range_int_cst_p (&vr1))
> - return false;
> -
> - tree r1 = int_const_binop (subcode, vr0.min, vr1.min);
> - tree r2 = int_const_binop (subcode, vr0.max, vr1.max);
> - if (r1 == NULL_TREE || TREE_OVERFLOW (r1)
> - || r2 == NULL_TREE || TREE_OVERFLOW (r2))
> - return false;
> - if (subcode == MULT_EXPR)
> + if (!range_int_cst_p (&vr0))
> + {
> + /* If one range is VR_ANTI_RANGE, VR_VARYING etc.,
> + optimize at least x = y + 0; x = y - 0; x = y * 0;
> + and x = y * 1; which never overflow. */
> + if (!range_int_cst_p (&vr1))
> + return false;
> + if (tree_int_cst_sgn (vr1.min) == -1)
> + return false;
> + if (compare_tree_int (vr1.max, subcode == MULT_EXPR) == 1)
> + return false;
> + }
> + else if (!range_int_cst_p (&vr1))
> + {
> + /* If one range is VR_ANTI_RANGE, VR_VARYING etc.,
> + optimize at least x = 0 + y; x = 0 * y; and x = 1 * y;
> + which never overflow. */
> + if (subcode == MINUS_EXPR)
> + return false;
> + if (!range_int_cst_p (&vr0))
> + return false;
> + if (tree_int_cst_sgn (vr0.min) == -1)
> + return false;
> + if (compare_tree_int (vr0.max, subcode == MULT_EXPR) == 1)
> + return false;
> + }
> + else
> {
> - tree r3 = int_const_binop (subcode, vr0.min, vr1.max);
> - tree r4 = int_const_binop (subcode, vr0.max, vr1.min);
> - if (r3 == NULL_TREE || TREE_OVERFLOW (r3)
> - || r4 == NULL_TREE || TREE_OVERFLOW (r4))
> + tree r1 = int_const_binop (subcode, vr0.min, vr1.min);
> + tree r2 = int_const_binop (subcode, vr0.max, vr1.max);
> + if (r1 == NULL_TREE || TREE_OVERFLOW (r1)
> + || r2 == NULL_TREE || TREE_OVERFLOW (r2))
> return false;
> + if (subcode == MULT_EXPR)
> + {
> + tree r3 = int_const_binop (subcode, vr0.min, vr1.max);
> + tree r4 = int_const_binop (subcode, vr0.max, vr1.min);
> + if (r3 == NULL_TREE || TREE_OVERFLOW (r3)
> + || r4 == NULL_TREE || TREE_OVERFLOW (r4))
> + return false;
> + }
> }
> +
> gimple g = gimple_build_assign_with_ops (subcode, gimple_call_lhs (stmt),
> op0, op1);
> gsi_replace (gsi, g, false);
> --- gcc/gimple-fold.c.jj 2014-03-18 17:08:48.000000000 +0100
> +++ gcc/gimple-fold.c 2014-03-25 12:04:07.277342445 +0100
> @@ -1186,13 +1186,56 @@ gimple_fold_call (gimple_stmt_iterator *
> else if (gimple_call_builtin_p (stmt, BUILT_IN_MD))
> changed |= targetm.gimple_fold_builtin (gsi);
> }
> - else if (gimple_call_internal_p (stmt)
> - && gimple_call_internal_fn (stmt) == IFN_BUILTIN_EXPECT)
> + else if (gimple_call_internal_p (stmt))
> {
> - tree result = fold_builtin_expect (gimple_location (stmt),
> - gimple_call_arg (stmt, 0),
> - gimple_call_arg (stmt, 1),
> - gimple_call_arg (stmt, 2));
> + enum tree_code subcode = ERROR_MARK;
> + tree result = NULL_TREE;
> + switch (gimple_call_internal_fn (stmt))
> + {
> + case IFN_BUILTIN_EXPECT:
> + result = fold_builtin_expect (gimple_location (stmt),
> + gimple_call_arg (stmt, 0),
> + gimple_call_arg (stmt, 1),
> + gimple_call_arg (stmt, 2));
> + break;
> + case IFN_UBSAN_CHECK_ADD:
> + subcode = PLUS_EXPR;
> + break;
> + case IFN_UBSAN_CHECK_SUB:
> + subcode = MINUS_EXPR;
> + break;
> + case IFN_UBSAN_CHECK_MUL:
> + subcode = MULT_EXPR;
> + break;
> + default:
> + break;
> + }
> + if (subcode != ERROR_MARK)
> + {
> + tree arg0 = gimple_call_arg (stmt, 0);
> + tree arg1 = gimple_call_arg (stmt, 1);
> + /* x = y + 0; x = y - 0; x = y * 0; */
> + if (integer_zerop (arg1))
> + result = subcode == MULT_EXPR
> + ? build_zero_cst (TREE_TYPE (arg0))
> + : arg0;
> + /* x = 0 + y; x = 0 * y; */
> + else if (subcode != MINUS_EXPR && integer_zerop (arg0))
> + result = subcode == MULT_EXPR
> + ? build_zero_cst (TREE_TYPE (arg0))
> + : arg1;
> + /* x = y - y; */
> + else if (subcode == MINUS_EXPR && operand_equal_p (arg0, arg1, 0))
> + result = build_zero_cst (TREE_TYPE (arg0));
> + /* x = y * 1; x = 1 * y; */
> + else if (subcode == MULT_EXPR)
> + {
> + if (integer_onep (arg1))
> + result = arg0;
> + else if (integer_onep (arg0))
> + result = arg1;
> + }
> + }
> if (result)
> {
> if (!update_call_from_tree (gsi, result))
> @@ -2688,15 +2731,32 @@ gimple_fold_stmt_to_constant_1 (gimple s
> default:
> return NULL_TREE;
> }
> - tree op0 = (*valueize) (gimple_call_arg (stmt, 0));
> - tree op1 = (*valueize) (gimple_call_arg (stmt, 1));
> + tree arg0 = gimple_call_arg (stmt, 0);
> + tree arg1 = gimple_call_arg (stmt, 1);
> + tree op0 = (*valueize) (arg0);
> + tree op1 = (*valueize) (arg1);
>
> if (TREE_CODE (op0) != INTEGER_CST
> || TREE_CODE (op1) != INTEGER_CST)
> - return NULL_TREE;
> - tree res = fold_binary_loc (loc, subcode,
> - TREE_TYPE (gimple_call_arg (stmt, 0)),
> - op0, op1);
> + {
> + switch (subcode)
> + {
> + case MULT_EXPR:
> + /* x * 0 = 0 * x = 0 without overflow. */
> + if (integer_zerop (op0) || integer_zerop (op1))
> + return build_zero_cst (TREE_TYPE (arg0));
> + break;
> + case MINUS_EXPR:
> + /* y - y = 0 without overflow. */
> + if (operand_equal_p (op0, op1, 0))
> + return build_zero_cst (TREE_TYPE (arg0));
> + break;
> + default:
> + break;
> + }
> + }
> + tree res
> + = fold_binary_loc (loc, subcode, TREE_TYPE (arg0), op0, op1);
> if (res
> && TREE_CODE (res) == INTEGER_CST
> && !TREE_OVERFLOW (res))
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imend"orffer
