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Re: [PATCH] Fold comparison of local addresses
On Wed, 26 Mar 2008, Richard Guenther wrote:
> On Wed, Mar 26, 2008 at 3:10 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> > Hi,
> >
> > This patch may be the cause for
> >
> > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35706
> >
> > I will know for sure within an hour.
>
> Bah, I have bootstrapped and tested a clean tree. I'll revert the
> patch for now.
Third try. This time with proper testing on x86_64-unknown-linux-gnu.
Apart from a typo the patch triggered a latent bug in VRP where that
was assuming that fold_binary_to_constant will either return NULL
or an integer constant. Which is not true as that function can
return anything that is TREE_CONSTANT. Whether "foo" < "bar" should
really be TREE_CONSTANT is another question though, but rather than
trying to reason about that I made VRP more robust here (VRP is
the only caller of fold_binary_to_constant with tcc_comparison
operators).
Thus, installed as follows.
Richard.
2008-03-26 Richard Guenther <rguenther@suse.de>
* fold-const.c (target.h): Include.
(fold_comparison): Fold comparison of addresses of decls
that bind locally or of constants. Consolidate address folding code.
* tree-vrp.c (operand_less_p): Deal with non-INTEGER_CST
results from fold_binary_to_constant.
(compare_values_warnv): Likewise.
* gcc.dg/fold-addr-1.c: New testcase.
Index: testsuite/gcc.dg/fold-addr-1.c
===================================================================
*** testsuite/gcc.dg/fold-addr-1.c (revision 0)
--- testsuite/gcc.dg/fold-addr-1.c (revision 0)
***************
*** 0 ****
--- 1,10 ----
+ /* { dg-do compile } */
+ /* { dg-options "-fdump-tree-original" } */
+
+ int bar(char p1, char p2)
+ {
+ return &p1 == &p2;
+ }
+
+ /* { dg-final { scan-tree-dump "return 0;" "original" } } */
+ /* { dg-final { cleanup-tree-dump "original" } } */
Index: tree-vrp.c
===================================================================
*** tree-vrp.c (revision 133613)
--- tree-vrp.c (working copy)
*************** operand_less_p (tree val, tree val2)
*** 724,730 ****
fold_undefer_and_ignore_overflow_warnings ();
! if (!tcmp)
return -2;
if (!integer_zerop (tcmp))
--- 724,731 ----
fold_undefer_and_ignore_overflow_warnings ();
! if (!tcmp
! || TREE_CODE (tcmp) != INTEGER_CST)
return -2;
if (!integer_zerop (tcmp))
*************** compare_values_warnv (tree val1, tree va
*** 932,938 ****
|| TREE_CODE (val2) != INTEGER_CST)
{
t = fold_binary_to_constant (NE_EXPR, boolean_type_node, val1, val2);
! if (t && tree_expr_nonzero_p (t))
return 2;
}
--- 933,939 ----
|| TREE_CODE (val2) != INTEGER_CST)
{
t = fold_binary_to_constant (NE_EXPR, boolean_type_node, val1, val2);
! if (t && integer_onep (t))
return 2;
}
Index: fold-const.c
===================================================================
*** fold-const.c (revision 133613)
--- fold-const.c (working copy)
*************** along with GCC; see the file COPYING3.
*** 58,63 ****
--- 58,64 ----
#include "rtl.h"
#include "expr.h"
#include "tm_p.h"
+ #include "target.h"
#include "toplev.h"
#include "intl.h"
#include "ggc.h"
*************** fold_comparison (enum tree_code code, tr
*** 8481,8491 ****
HOST_WIDE_INT bitsize, bitpos0 = 0, bitpos1 = 0;
enum machine_mode mode;
int volatilep, unsignedp;
! bool indirect_base0 = false;
/* Get base and offset for the access. Strip ADDR_EXPR for
get_inner_reference, but put it back by stripping INDIRECT_REF
! off the base object if possible. */
base0 = arg0;
if (TREE_CODE (arg0) == ADDR_EXPR)
{
--- 8482,8493 ----
HOST_WIDE_INT bitsize, bitpos0 = 0, bitpos1 = 0;
enum machine_mode mode;
int volatilep, unsignedp;
! bool indirect_base0 = false, indirect_base1 = false;
/* Get base and offset for the access. Strip ADDR_EXPR for
get_inner_reference, but put it back by stripping INDIRECT_REF
! off the base object if possible. indirect_baseN will be true
! if baseN is not an address but refers to the object itself. */
base0 = arg0;
if (TREE_CODE (arg0) == ADDR_EXPR)
{
*************** fold_comparison (enum tree_code code, tr
*** 8509,8532 ****
base1 = get_inner_reference (TREE_OPERAND (arg1, 0),
&bitsize, &bitpos1, &offset1, &mode,
&unsignedp, &volatilep, false);
! /* We have to make sure to have an indirect/non-indirect base1
! just the same as we did for base0. */
! if (TREE_CODE (base1) == INDIRECT_REF
! && !indirect_base0)
base1 = TREE_OPERAND (base1, 0);
! else if (!indirect_base0)
! base1 = NULL_TREE;
}
else if (TREE_CODE (arg1) == POINTER_PLUS_EXPR)
{
base1 = TREE_OPERAND (arg1, 0);
offset1 = TREE_OPERAND (arg1, 1);
}
- else if (indirect_base0)
- base1 = NULL_TREE;
/* If we have equivalent bases we might be able to simplify. */
! if (base0 && base1
&& operand_equal_p (base0, base1, 0))
{
/* We can fold this expression to a constant if the non-constant
--- 8511,8529 ----
base1 = get_inner_reference (TREE_OPERAND (arg1, 0),
&bitsize, &bitpos1, &offset1, &mode,
&unsignedp, &volatilep, false);
! if (TREE_CODE (base1) == INDIRECT_REF)
base1 = TREE_OPERAND (base1, 0);
! else
! indirect_base1 = true;
}
else if (TREE_CODE (arg1) == POINTER_PLUS_EXPR)
{
base1 = TREE_OPERAND (arg1, 0);
offset1 = TREE_OPERAND (arg1, 1);
}
/* If we have equivalent bases we might be able to simplify. */
! if (indirect_base0 == indirect_base1
&& operand_equal_p (base0, base1, 0))
{
/* We can fold this expression to a constant if the non-constant
*************** fold_comparison (enum tree_code code, tr
*** 8581,8586 ****
--- 8578,8621 ----
return fold_build2 (code, type, offset0, offset1);
}
}
+ /* For non-equal bases we can simplify if they are addresses
+ of local binding decls or constants. */
+ else if (indirect_base0 && indirect_base1
+ /* We know that !operand_equal_p (base0, base1, 0)
+ because the if condition was false. */
+ && TREE_CODE (arg0) == ADDR_EXPR
+ && TREE_CODE (arg1) == ADDR_EXPR
+ && ((DECL_P (base0)
+ && (targetm.binds_local_p (base0)
+ || CONSTANT_CLASS_P (base1)))
+ || CONSTANT_CLASS_P (base0))
+ && ((DECL_P (base1)
+ && (targetm.binds_local_p (base1)
+ || CONSTANT_CLASS_P (base0)))
+ || CONSTANT_CLASS_P (base1)))
+ {
+ if (code == EQ_EXPR)
+ return omit_two_operands (type, boolean_false_node, arg0, arg1);
+ else if (code == NE_EXPR)
+ return omit_two_operands (type, boolean_true_node, arg0, arg1);
+ }
+ /* For equal offsets we can simplify to a comparison of the
+ base addresses. */
+ else if (bitpos0 == bitpos1
+ && (indirect_base0
+ ? base0 != TREE_OPERAND (arg0, 0) : base0 != arg0)
+ && (indirect_base1
+ ? base1 != TREE_OPERAND (arg1, 0) : base1 != arg1)
+ && ((offset0 == offset1)
+ || (offset0 && offset1
+ && operand_equal_p (offset0, offset1, 0))))
+ {
+ if (indirect_base0)
+ base0 = fold_addr_expr (base0);
+ if (indirect_base1)
+ base1 = fold_addr_expr (base1);
+ return fold_build2 (code, type, base0, base1);
+ }
}
/* Transform comparisons of the form X +- C1 CMP Y +- C2 to
*************** fold_comparison (enum tree_code code, tr
*** 8927,8953 ****
}
}
- /* Fold a comparison of the address of COMPONENT_REFs with the same
- type and component to a comparison of the address of the base
- object. In short, &x->a OP &y->a to x OP y and
- &x->a OP &y.a to x OP &y */
- if (TREE_CODE (arg0) == ADDR_EXPR
- && TREE_CODE (TREE_OPERAND (arg0, 0)) == COMPONENT_REF
- && TREE_CODE (arg1) == ADDR_EXPR
- && TREE_CODE (TREE_OPERAND (arg1, 0)) == COMPONENT_REF)
- {
- tree cref0 = TREE_OPERAND (arg0, 0);
- tree cref1 = TREE_OPERAND (arg1, 0);
- if (TREE_OPERAND (cref0, 1) == TREE_OPERAND (cref1, 1))
- {
- tree op0 = TREE_OPERAND (cref0, 0);
- tree op1 = TREE_OPERAND (cref1, 0);
- return fold_build2 (code, type,
- fold_addr_expr (op0),
- fold_addr_expr (op1));
- }
- }
-
/* We can fold X/C1 op C2 where C1 and C2 are integer constants
into a single range test. */
if ((TREE_CODE (arg0) == TRUNC_DIV_EXPR
--- 8962,8967 ----