The following patch avoids rewriting virtual SSA after each if-converted
loop (possibly).
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2016-08-18 Richard Biener <rguent...@suse.de>
* ssa-iterators.h (ssa_vuse_operand): New inline.
* tree-if-conv.c (ifc_temp_var): Update virtual operand.
(predicate_all_scalar_phis): Use remove_phi_node to remove
phi nodes predicated. Delay removing virtual PHIs.
(predicate_mem_writes): Update virtual operands.
(combine_blocks): Likewise. Propagate out remaining virtual PHIs.
(tree_if_conversion): Do not rewrite virtual SSA form.
* tree-phinodes.c (release_phi_node): Make static.
* tree-phinodes.h (release_phi_node): Remove.
Index: gcc/ssa-iterators.h
===================================================================
--- gcc/ssa-iterators.h (revision 239529)
+++ gcc/ssa-iterators.h (working copy)
@@ -699,6 +699,15 @@ single_ssa_use_operand (gimple *stmt, in
return NULL_USE_OPERAND_P;
}
+/* Return the single virtual use operand in STMT if present. Otherwise
+ return NULL. */
+static inline use_operand_p
+ssa_vuse_operand (gimple *stmt)
+{
+ if (! gimple_vuse (stmt))
+ return NULL_USE_OPERAND_P;
+ return USE_OP_PTR (gimple_use_ops (stmt));
+}
/* If there is a single operand in STMT matching FLAGS, return it. Otherwise
Index: gcc/tree-if-conv.c
===================================================================
--- gcc/tree-if-conv.c (revision 239529)
+++ gcc/tree-if-conv.c (working copy)
@@ -326,6 +326,7 @@ ifc_temp_var (tree type, tree expr, gimp
{
tree new_name = make_temp_ssa_name (type, NULL, "_ifc_");
gimple *stmt = gimple_build_assign (new_name, expr);
+ gimple_set_vuse (stmt, gimple_vuse (gsi_stmt (*gsi)));
gsi_insert_before (gsi, stmt, GSI_SAME_STMT);
return new_name;
}
@@ -1946,12 +1947,14 @@ predicate_all_scalar_phis (struct loop *
while (!gsi_end_p (phi_gsi))
{
phi = phi_gsi.phi ();
- predicate_scalar_phi (phi, &gsi);
- release_phi_node (phi);
- gsi_next (&phi_gsi);
+ if (virtual_operand_p (gimple_phi_result (phi)))
+ gsi_next (&phi_gsi);
+ else
+ {
+ predicate_scalar_phi (phi, &gsi);
+ remove_phi_node (&phi_gsi, false);
+ }
}
-
- set_phi_nodes (bb, NULL);
}
}
@@ -2218,11 +2221,18 @@ predicate_mem_writes (loop_p loop)
= gimple_build_call_internal (IFN_MASK_LOAD, 3, addr,
ptr, mask);
gimple_call_set_lhs (new_stmt, lhs);
+ gimple_set_vuse (new_stmt, gimple_vuse (stmt));
}
else
- new_stmt
- = gimple_build_call_internal (IFN_MASK_STORE, 4, addr, ptr,
- mask, rhs);
+ {
+ new_stmt
+ = gimple_build_call_internal (IFN_MASK_STORE, 4, addr, ptr,
+ mask, rhs);
+ gimple_set_vuse (new_stmt, gimple_vuse (stmt));
+ gimple_set_vdef (new_stmt, gimple_vdef (stmt));
+ SSA_NAME_DEF_STMT (gimple_vdef (new_stmt)) = new_stmt;
+ }
+
gsi_replace (&gsi, new_stmt, true);
}
else if (gimple_vdef (stmt))
@@ -2361,6 +2371,20 @@ combine_blocks (struct loop *loop)
}
merge_target_bb = loop->header;
+
+ /* Get at the virtual def valid for uses starting at the first block
+ we merge into the header. Without a virtual PHI the loop has the
+ same virtual use on all stmts. */
+ gphi *vphi = get_virtual_phi (loop->header);
+ tree last_vdef = NULL_TREE;
+ if (vphi)
+ {
+ last_vdef = gimple_phi_result (vphi);
+ for (gimple_stmt_iterator gsi = gsi_start_bb (loop->header);
+ ! gsi_end_p (gsi); gsi_next (&gsi))
+ if (gimple_vdef (gsi_stmt (gsi)))
+ last_vdef = gimple_vdef (gsi_stmt (gsi));
+ }
for (i = 1; i < orig_loop_num_nodes; i++)
{
gimple_stmt_iterator gsi;
@@ -2371,6 +2395,24 @@ combine_blocks (struct loop *loop)
if (bb == exit_bb || bb == loop->latch)
continue;
+ /* We release virtual PHIs late because we have to propagate them
+ out using the current VUSE. The def might be the one used
+ after the loop. */
+ vphi = get_virtual_phi (bb);
+ if (vphi)
+ {
+ imm_use_iterator iter;
+ use_operand_p use_p;
+ gimple *use_stmt;
+ FOR_EACH_IMM_USE_STMT (use_stmt, iter, gimple_phi_result (vphi))
+ {
+ FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+ SET_USE (use_p, last_vdef);
+ }
+ gsi = gsi_for_stmt (vphi);
+ remove_phi_node (&gsi, true);
+ }
+
/* Make stmts member of loop->header and clear range info from all stmts
in BB which is now no longer executed conditional on a predicate we
could have derived it from. */
@@ -2378,6 +2420,16 @@ combine_blocks (struct loop *loop)
{
gimple *stmt = gsi_stmt (gsi);
gimple_set_bb (stmt, merge_target_bb);
+ /* Update virtual operands. */
+ if (last_vdef)
+ {
+ use_operand_p use_p = ssa_vuse_operand (stmt);
+ if (use_p
+ && USE_FROM_PTR (use_p) != last_vdef)
+ SET_USE (use_p, last_vdef);
+ if (gimple_vdef (stmt))
+ last_vdef = gimple_vdef (stmt);
+ }
if (predicated[i])
{
ssa_op_iter i;
@@ -2389,7 +2441,7 @@ combine_blocks (struct loop *loop)
/* Update stmt list. */
last = gsi_last_bb (merge_target_bb);
- gsi_insert_seq_after (&last, bb_seq (bb), GSI_NEW_STMT);
+ gsi_insert_seq_after_without_update (&last, bb_seq (bb), GSI_NEW_STMT);
set_bb_seq (bb, NULL);
delete_basic_block (bb);
@@ -2399,9 +2451,29 @@ combine_blocks (struct loop *loop)
This reduces the number of basic blocks to two, to please the
vectorizer that handles only loops with two nodes. */
if (exit_bb
- && exit_bb != loop->header
- && can_merge_blocks_p (loop->header, exit_bb))
- merge_blocks (loop->header, exit_bb);
+ && exit_bb != loop->header)
+ {
+ /* We release virtual PHIs late because we have to propagate them
+ out using the current VUSE. The def might be the one used
+ after the loop. */
+ vphi = get_virtual_phi (exit_bb);
+ if (vphi)
+ {
+ imm_use_iterator iter;
+ use_operand_p use_p;
+ gimple *use_stmt;
+ FOR_EACH_IMM_USE_STMT (use_stmt, iter, gimple_phi_result (vphi))
+ {
+ FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+ SET_USE (use_p, last_vdef);
+ }
+ gimple_stmt_iterator gsi = gsi_for_stmt (vphi);
+ remove_phi_node (&gsi, true);
+ }
+
+ if (can_merge_blocks_p (loop->header, exit_bb))
+ merge_blocks (loop->header, exit_bb);
+ }
free (ifc_bbs);
ifc_bbs = NULL;
@@ -2669,8 +2741,6 @@ tree_if_conversion (struct loop *loop)
ifcvt_local_dce (loop->header);
todo |= TODO_cleanup_cfg;
- mark_virtual_operands_for_renaming (cfun);
- todo |= TODO_update_ssa_only_virtuals;
cleanup:
if (ifc_bbs)
Index: gcc/tree-phinodes.c
===================================================================
--- gcc/tree-phinodes.c (revision 239531)
+++ gcc/tree-phinodes.c (working copy)
@@ -207,7 +207,7 @@ make_phi_node (tree var, int len)
/* We no longer need PHI, release it so that it may be reused. */
-void
+static void
release_phi_node (gimple *phi)
{
size_t bucket;
Index: gcc/tree-phinodes.h
===================================================================
--- gcc/tree-phinodes.h (revision 239531)
+++ gcc/tree-phinodes.h (working copy)
@@ -21,7 +21,6 @@ along with GCC; see the file COPYING3.
#define GCC_TREE_PHINODES_H
extern void phinodes_print_statistics (void);
-extern void release_phi_node (gimple *);
extern void reserve_phi_args_for_new_edge (basic_block);
extern void add_phi_node_to_bb (gphi *phi, basic_block bb);
extern gphi *create_phi_node (tree, basic_block);
