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[PATCH] Improve PTA to not make all indirectly stored pointers escaped
- From: Richard Guenther <rguenther at suse dot de>
- To: gcc-patches at gcc dot gnu dot org
- Date: Tue, 16 Jun 2009 14:27:12 +0200 (CEST)
- Subject: [PATCH] Improve PTA to not make all indirectly stored pointers escaped
This improves PTA so that we can optimize
int *q;
void __attribute__((noinline))
bar (void)
{
*q = 1;
}
int foo(int which_p)
{
int x = 0;
int *i,*j;
int **p;
if (which_p)
p = &i;
else
p = &j;
*p = &x;
bar ();
return x;
}
to return 0. Previously the store *p = &x made x escape even though
p only points to local memory.
This should especially help for early points-to analysis but is also
a requirement for IPA-PTA to do anything meaningful.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2009-06-16 Richard Guenther <rguenther@suse.de>
* tree-ssa-structalias.c (do_ds_constraint): Stores in global
variables add them to ESCAPED.
(find_func_aliases): Do not make all indirectly stored values
escaped.
* gcc.dg/tree-ssa/pta-escape-1.c: New testcase.
* gcc.dg/tree-ssa/pta-escape-2.c: Likewise.
* gcc.dg/tree-ssa/pta-escape-3.c: Likewise.
* gcc.dg/tree-ssa/ssa-fre-27.c: Likewise.
Index: gcc/tree-ssa-structalias.c
===================================================================
*** gcc/tree-ssa-structalias.c.orig 2009-06-16 11:56:41.000000000 +0200
--- gcc/tree-ssa-structalias.c 2009-06-16 12:25:18.000000000 +0200
*************** do_ds_constraint (constraint_t c, bitmap
*** 1664,1669 ****
--- 1664,1682 ----
unsigned int t;
HOST_WIDE_INT fieldoffset = v->offset + loff;
+ /* If v is a NONLOCAL then this is an escape point. */
+ if (j == nonlocal_id)
+ {
+ t = find (escaped_id);
+ if (add_graph_edge (graph, t, rhs)
+ && bitmap_ior_into (get_varinfo (t)->solution, sol)
+ && !TEST_BIT (changed, t))
+ {
+ SET_BIT (changed, t);
+ changed_count++;
+ }
+ }
+
if (v->is_special_var)
continue;
*************** do_ds_constraint (constraint_t c, bitmap
*** 1680,1697 ****
if (v->may_have_pointers)
{
t = find (v->id);
! if (add_graph_edge (graph, t, rhs))
{
! if (bitmap_ior_into (get_varinfo (t)->solution, sol))
! {
! if (t == rhs)
! sol = get_varinfo (rhs)->solution;
! if (!TEST_BIT (changed, t))
! {
! SET_BIT (changed, t);
! changed_count++;
! }
! }
}
}
--- 1693,1716 ----
if (v->may_have_pointers)
{
t = find (v->id);
! if (add_graph_edge (graph, t, rhs)
! && bitmap_ior_into (get_varinfo (t)->solution, sol)
! && !TEST_BIT (changed, t))
{
! SET_BIT (changed, t);
! changed_count++;
! }
! }
! /* If v is a global variable then this is an escape point. */
! if (is_global_var (v->decl))
! {
! t = find (escaped_id);
! if (add_graph_edge (graph, t, rhs)
! && bitmap_ior_into (get_varinfo (t)->solution, sol)
! && !TEST_BIT (changed, t))
! {
! SET_BIT (changed, t);
! changed_count++;
}
}
*************** find_func_aliases (gimple origt)
*** 3734,3764 ****
process_constraint (new_constraint (*c, *c2));
}
}
}
stmt_escape_type = is_escape_site (t);
! if (stmt_escape_type == ESCAPE_STORED_IN_GLOBAL)
! {
! gcc_assert (is_gimple_assign (t));
! if (gimple_assign_rhs_code (t) == ADDR_EXPR)
! {
! tree rhs = gimple_assign_rhs1 (t);
! tree base = get_base_address (TREE_OPERAND (rhs, 0));
! if (base
! && (!DECL_P (base)
! || !is_global_var (base)))
! make_escape_constraint (rhs);
! }
! else if (get_gimple_rhs_class (gimple_assign_rhs_code (t))
! == GIMPLE_SINGLE_RHS)
! {
! if (could_have_pointers (gimple_assign_rhs1 (t)))
! make_escape_constraint (gimple_assign_rhs1 (t));
! }
! else
! gcc_unreachable ();
! }
! else if (stmt_escape_type == ESCAPE_BAD_CAST)
{
gcc_assert (is_gimple_assign (t));
gcc_assert (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (t))
--- 3753,3767 ----
process_constraint (new_constraint (*c, *c2));
}
}
+ /* If there is a store to a global variable the rhs escapes. */
+ if ((lhsop = get_base_address (lhsop)) != NULL_TREE
+ && DECL_P (lhsop)
+ && is_global_var (lhsop))
+ make_escape_constraint (rhsop);
}
stmt_escape_type = is_escape_site (t);
! if (stmt_escape_type == ESCAPE_BAD_CAST)
{
gcc_assert (is_gimple_assign (t));
gcc_assert (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (t))
Index: gcc/testsuite/gcc.dg/tree-ssa/pta-escape-1.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.dg/tree-ssa/pta-escape-1.c 2009-06-16 12:10:42.000000000 +0200
***************
*** 0 ****
--- 1,37 ----
+ /* { dg-do run } */
+ /* { dg-options "-O -fdump-tree-alias-details" } */
+
+ int *i;
+ void __attribute__((noinline))
+ foo (void)
+ {
+ *i = 1;
+ }
+ int __attribute__((noinline))
+ bar(int local_p)
+ {
+ int x = 0;
+ int *j;
+ int **p;
+ if (local_p)
+ p = &j;
+ else
+ p = &i;
+ *p = &x; /* This makes x escape. */
+ foo ();
+ return x;
+ }
+ extern void abort (void);
+ int main()
+ {
+ int k = 2;
+ i = &k;
+ if (bar (1) != 0 || k != 1)
+ abort ();
+ if (bar (0) != 1)
+ abort ();
+ return 0;
+ }
+
+ /* { dg-final { scan-tree-dump "ESCAPED, points-to vars: { x }" "alias" } } */
+ /* { dg-final { cleanup-tree-dump "alias" } } */
Index: gcc/testsuite/gcc.dg/tree-ssa/pta-escape-2.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.dg/tree-ssa/pta-escape-2.c 2009-06-16 12:26:18.000000000 +0200
***************
*** 0 ****
--- 1,38 ----
+ /* { dg-do run } */
+ /* { dg-options "-O -fdump-tree-alias-details" } */
+
+ int *i;
+ void __attribute__((noinline))
+ foo (void)
+ {
+ *i = 1;
+ }
+ int __attribute__((noinline))
+ bar(int local_p, int **q)
+ {
+ int x = 0;
+ int *j;
+ int **p;
+ if (local_p)
+ p = &j;
+ else
+ p = q;
+ *p = &x; /* This makes x escape. */
+ foo ();
+ return x;
+ }
+ extern void abort (void);
+ int main()
+ {
+ int k = 2;
+ int **q = &i;
+ i = &k;
+ if (bar (1, q) != 0 || k != 1)
+ abort ();
+ if (bar (0, q) != 1)
+ abort ();
+ return 0;
+ }
+
+ /* { dg-final { scan-tree-dump "ESCAPED, points-to vars: { x }" "alias" } } */
+ /* { dg-final { cleanup-tree-dump "alias" } } */
Index: gcc/testsuite/gcc.dg/tree-ssa/pta-escape-3.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.dg/tree-ssa/pta-escape-3.c 2009-06-16 12:28:29.000000000 +0200
***************
*** 0 ****
--- 1,42 ----
+ /* { dg-do run } */
+ /* { dg-options "-O -fdump-tree-alias-details" } */
+
+ int *i;
+ void __attribute__((noinline))
+ foo (void)
+ {
+ *i = 1;
+ }
+ int **__attribute__((noinline,const))
+ foobar (void)
+ {
+ return &i;
+ }
+ int __attribute__((noinline))
+ bar(int local_p)
+ {
+ int x = 0;
+ int *j;
+ int **p;
+ if (local_p)
+ p = &j;
+ else
+ p = foobar();
+ *p = &x; /* This makes x escape. */
+ foo ();
+ return x;
+ }
+ extern void abort (void);
+ int main()
+ {
+ int k = 2;
+ i = &k;
+ if (bar (1) != 0 || k != 1)
+ abort ();
+ if (bar (0) != 1)
+ abort ();
+ return 0;
+ }
+
+ /* { dg-final { scan-tree-dump "ESCAPED, points-to vars: { x }" "alias" } } */
+ /* { dg-final { cleanup-tree-dump "alias" } } */
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-27.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-27.c 2009-06-16 12:36:12.000000000 +0200
***************
*** 0 ****
--- 1,25 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-fre-details" } */
+
+ int *q;
+ void __attribute__((noinline))
+ bar (void)
+ {
+ *q = 1;
+ }
+ int foo(int which_p)
+ {
+ int x = 0;
+ int *i,*j;
+ int **p;
+ if (which_p)
+ p = &i;
+ else
+ p = &j;
+ *p = &x;
+ bar ();
+ return x;
+ }
+
+ /* { dg-final { scan-tree-dump "Replaced x with 0" "fre" } } */
+ /* { dg-final { cleanup-tree-dump "fre" } } */