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Re: [PATCH] Fix folding of UBSAN_CHECK_SUB (x, 0) etc.
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Richard Biener <rguenther at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Tue, 25 Mar 2014 20:20:15 +0100
- Subject: Re: [PATCH] Fix folding of UBSAN_CHECK_SUB (x, 0) etc.
- Authentication-results: sourceware.org; auth=none
- References: <20140325072800 dot GL1817 at tucnak dot redhat dot com> <alpine dot LSU dot 2 dot 11 dot 1403251011030 dot 26135 at zhemvz dot fhfr dot qr> <alpine dot LSU dot 2 dot 11 dot 1403251013400 dot 26135 at zhemvz dot fhfr dot qr>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
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?
2014-03-25 Jakub Jelinek <jakub@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