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Re: [PATCH] Fold comparison of local addresses
- From: Richard Guenther <rguenther at suse dot de>
- To: gcc-patches at gcc dot gnu dot org
- Date: Wed, 26 Mar 2008 13:35:20 +0100 (CET)
- Subject: Re: [PATCH] Fold comparison of local addresses
- References: <Pine.LNX.4.64.0803251546051.4133@zhemvz.fhfr.qr>
On Tue, 25 Mar 2008, Richard Guenther wrote:
>
> I was surprised we don't handle this yet.
>
> Bootstrap & regtest in progress, I'll apply it after that succeeded.
I ended up with a different patch, which is as below.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to
mainline.
Richard.
2008-03-26 Richard Guenther <rguenther@suse.de>
* fold-const.c (target.h): Include.
(fold_comparison): Fold comparison of addresses of two decls
that bind locally. Consolidate address folding code.
* 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: fold-const.c
===================================================================
*** fold-const.c (revision 133506)
--- 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 ****
--- 8578,8614 ----
return fold_build2 (code, type, offset0, offset1);
}
}
+ /* For non-equal bases we can simplify if they are plain decls. */
+ else if (!indirect_base0 && !indirect_base1
+ && TREE_CODE (arg0) == ADDR_EXPR
+ && TREE_CODE (arg1) == ADDR_EXPR
+ && DECL_P (base0) && DECL_P (base1)
+ && !operand_equal_p (base0, base1, 0)
+ && targetm.binds_local_p (base0)
+ && targetm.binds_local_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
--- 8955,8960 ----