There are two basic errors in the computation - the first is when
min_cost is never adjusted it remains at UINT_MAX (happens when
all PHI arguments are not defined in any loop). Second is if
the PHI argument is not defined in the same loop as the PHI - then
we accumulate the cost of already invariant stmts (inconsistently
with the LIM cost modelling).
Bootstrap and regtest running on x86_64-unknown-linux-gnu.
Richard.
2014-06-16 Richard Biener <rguent...@suse.de>
* tree-ssa-loop-im.c (determine_max_movement): Adjust cost
of PHI node moving.
* gcc.dg/tree-ssa/ssa-lim-12.c: New testcase.
Index: gcc/tree-ssa-loop-im.c
===================================================================
*** gcc/tree-ssa-loop-im.c (revision 211698)
--- gcc/tree-ssa-loop-im.c (working copy)
*************** determine_max_movement (gimple stmt, boo
*** 729,742 ****
}
if (!add_dependency (val, lim_data, loop, false))
return false;
! def_data = get_lim_data (SSA_NAME_DEF_STMT (val));
! if (def_data)
{
! min_cost = MIN (min_cost, def_data->cost);
! total_cost += def_data->cost;
}
}
lim_data->cost += min_cost;
if (gimple_phi_num_args (stmt) > 1)
--- 732,752 ----
}
if (!add_dependency (val, lim_data, loop, false))
return false;
!
! gimple def_stmt = SSA_NAME_DEF_STMT (val);
! if (gimple_bb (def_stmt)
! && gimple_bb (def_stmt)->loop_father == loop)
{
! def_data = get_lim_data (def_stmt);
! if (def_data)
! {
! min_cost = MIN (min_cost, def_data->cost);
! total_cost += def_data->cost;
! }
}
}
+ min_cost = MIN (min_cost, total_cost);
lim_data->cost += min_cost;
if (gimple_phi_num_args (stmt) > 1)
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-lim-12.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/ssa-lim-12.c (revision 0)
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-lim-12.c (working copy)
***************
*** 0 ****
--- 1,27 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-lim1" } */
+
+ int a[1024];
+
+ void foo (int x, int z)
+ {
+ int i;
+ int y = -x;
+ for (i = 0; i < 1024; ++i)
+ a[i] = x ? y : z;
+ }
+
+ void bar (int x, int z)
+ {
+ int j;
+ for (j = 0; j < 1024; ++j)
+ {
+ int i;
+ int y = -j + z;
+ for (i = 0; i < 1024; ++i)
+ a[i] = x ? y : j;
+ }
+ }
+
+ /* { dg-final { scan-tree-dump-times "!= 0 ? " 2 "lim1" } } */
+ /* { dg-final { cleanup-tree-dump "lim1" } } */
