The following fixes CH - FRE - LIM not doing store-motion across a loop
nest for redundant header checks. FRE is supposed to do such
redundant comparison "threading" but didn't do it because of latch
edges confusing the single_pred_p check.
The following fixes it by disregarding edges that come from blocks
we dominate.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2015-11-23 Richard Biener <rguent...@suse.de>
PR tree-optimization/68465
* tree-ssa-sccvn.c (sccvn_dom_walker::before_dom_children):
Also record equalities from multiple predecessor blocks if
only one non-backedge exists.
* gcc.dg/tree-ssa/ssa-fre-52.c: New testcase.
Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c (revision 230737)
--- gcc/tree-ssa-sccvn.c (working copy)
*************** sccvn_dom_walker::before_dom_children (b
*** 4357,4376 ****
/* If we have a single predecessor record the equivalence from a
possible condition on the predecessor edge. */
! if (single_pred_p (bb))
{
- edge e = single_pred_edge (bb);
/* Check if there are multiple executable successor edges in
the source block. Otherwise there is no additional info
to be recorded. */
edge e2;
! FOR_EACH_EDGE (e2, ei, e->src->succs)
! if (e2 != e
&& e2->flags & EDGE_EXECUTABLE)
break;
if (e2 && (e2->flags & EDGE_EXECUTABLE))
{
! gimple *stmt = last_stmt (e->src);
if (stmt
&& gimple_code (stmt) == GIMPLE_COND)
{
--- 4402,4435 ----
/* If we have a single predecessor record the equivalence from a
possible condition on the predecessor edge. */
! edge pred_e = NULL;
! FOR_EACH_EDGE (e, ei, bb->preds)
! {
! /* Ignore simple backedges from this to allow recording conditions
! in loop headers. */
! if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
! continue;
! if (! pred_e)
! pred_e = e;
! else
! {
! pred_e = NULL;
! break;
! }
! }
! if (pred_e)
{
/* Check if there are multiple executable successor edges in
the source block. Otherwise there is no additional info
to be recorded. */
edge e2;
! FOR_EACH_EDGE (e2, ei, pred_e->src->succs)
! if (e2 != pred_e
&& e2->flags & EDGE_EXECUTABLE)
break;
if (e2 && (e2->flags & EDGE_EXECUTABLE))
{
! gimple *stmt = last_stmt (pred_e->src);
if (stmt
&& gimple_code (stmt) == GIMPLE_COND)
{
*************** sccvn_dom_walker::before_dom_children (b
*** 4378,4388 ****
tree lhs = gimple_cond_lhs (stmt);
tree rhs = gimple_cond_rhs (stmt);
record_conds (bb, code, lhs, rhs,
! (e->flags & EDGE_TRUE_VALUE) != 0);
code = invert_tree_comparison (code, HONOR_NANS (lhs));
if (code != ERROR_MARK)
record_conds (bb, code, lhs, rhs,
! (e->flags & EDGE_TRUE_VALUE) == 0);
}
}
}
--- 4437,4447 ----
tree lhs = gimple_cond_lhs (stmt);
tree rhs = gimple_cond_rhs (stmt);
record_conds (bb, code, lhs, rhs,
! (pred_e->flags & EDGE_TRUE_VALUE) != 0);
code = invert_tree_comparison (code, HONOR_NANS (lhs));
if (code != ERROR_MARK)
record_conds (bb, code, lhs, rhs,
! (pred_e->flags & EDGE_TRUE_VALUE) == 0);
}
}
}
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-52.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-52.c (revision 0)
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-52.c (working copy)
***************
*** 0 ****
--- 1,26 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-fre1" } */
+
+ void bar ();
+ void foo (int n)
+ {
+ if (n > 0)
+ {
+ int j = 0;
+ do
+ {
+ if (n > 0)
+ {
+ int i = 0;
+ do
+ {
+ bar ();
+ }
+ while (i < n);
+ }
+ }
+ while (j < n);
+ }
+ }
+
+ /* { dg-final { scan-tree-dump-times "if" 1 "fre1" } } */
