tree-optimization/97623 - Avoid PRE hoist insertion iteration

The recent previous change in this area limited hoist insertion
iteration via a param but the following is IMHO better since
we are not really interested in PRE opportunities exposed by
hoisting but only the other way around.  So this moves hoist
insertion after PRE iteration finished and removes hoist
insertion iteration alltogether.

2020-11-11  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/97623
	* params.opt (-param=max-pre-hoist-insert-iterations): Remove
	again.
	* doc/invoke.texi (max-pre-hoist-insert-iterations): Likewise.
	* tree-ssa-pre.c (insert): Move hoist insertion after PRE
	insertion iteration and do not iterate it.

	* gcc.dg/tree-ssa/ssa-hoist-3.c: Adjust.
	* gcc.dg/tree-ssa/ssa-hoist-7.c: Likewise.
	* gcc.dg/tree-ssa/ssa-pre-30.c: Likewise.

6 files changed, 26 insertions, 25 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 18ca759..8d0d213 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -13446,11 +13446,6 @@ is aborted and the load or store is not considered redundant.  The
 number of queries is algorithmically limited to the number of
 stores on all paths from the load to the function entry.
 
-@item max-pre-hoist-insert-iterations
-The maximum number of iterations doing insertion during code
-hoisting which is done as part of the partial redundancy elimination
-insertion phase.
-
 @item ira-max-loops-num
 IRA uses regional register allocation by default.  If a function
 contains more loops than the number given by this parameter, only at most
diff --git a/gcc/params.opt b/gcc/params.opt
index a33a371..7bac39a 100644
--- a/gcc/params.opt
+++ b/gcc/params.opt
@@ -597,10 +597,6 @@ Maximum depth of sqrt chains to use when synthesizing exponentiation by a real c
 Common Joined UInteger Var(param_max_predicted_iterations) Init(100) IntegerRange(0, 65536) Param Optimization
 The maximum number of loop iterations we predict statically.
 
--param=max-pre-hoist-insert-iterations=
-Common Joined UInteger Var(param_max_pre_hoist_insert_iterations) Init(3) Param Optimization
-The maximum number of insert iterations done for PRE code hoisting.
-
 -param=max-reload-search-insns=
 Common Joined UInteger Var(param_max_reload_search_insns) Init(100) Param Optimization
 The maximum number of instructions to search backward when looking for equivalent reload.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-3.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-3.c
index 51ba59c..de3051b 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-3.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-3.c
@@ -15,4 +15,4 @@ int test (int a, int b, int c, int g)
 /* We should hoist and CSE only the multiplication.  */
 
 /* { dg-final { scan-tree-dump-times " \\* " 1 "pre" } } */
-/* { dg-final { scan-tree-dump "Insertions: 1" "pre" } } */
+/* { dg-final { scan-tree-dump "HOIST inserted: 1" "pre" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c
index ce9cec6..fdb6a3e 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c
@@ -49,6 +49,6 @@ void foo (int a, int b, int c, int d, int e, int x, int y, int z)
 
 /* Now inserting x + y five times is unnecessary but the cascading
    cannot be avoided with the simple-minded dataflow.  But make sure
-   we do the insertions all in the first iteration.  */
-/* { dg-final { scan-tree-dump "insert iterations == 2" "pre" } } */
+   we do not iterate PRE insertion.  */
+/* { dg-final { scan-tree-dump "insert iterations == 1" "pre" } } */
 /* { dg-final { scan-tree-dump "HOIST inserted: 5" "pre" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-30.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-30.c
index 59af63a..cf93173 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-30.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-30.c
@@ -24,4 +24,4 @@ bar (int b, int x)
 /* We should see the partial redundant loads of f even though they
    are using different types (of the same size).  */
 
-/* { dg-final { scan-tree-dump-times "Replaced MEM" 2 "pre" } } */
+/* { dg-final { scan-tree-dump-times "Replaced MEM" 3 "pre" } } */
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index da2b689..d90249c 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -3695,18 +3695,6 @@ insert (void)
 	fprintf (dump_file, "Starting insert iteration %d\n", num_iterations);
 
       changed = false;
-      /* Insert expressions for hoisting.  Do a backward walk here since
-	 inserting into BLOCK exposes new opportunities in its predecessors.
-	 Since PRE and hoist insertions can cause back-to-back iteration
-	 limit that on the hoist side.  */
-      if (flag_code_hoisting
-	  && num_iterations <= param_max_pre_hoist_insert_iterations)
-	for (int idx = rpo_num - 1; idx >= 0; --idx)
-	  {
-	    basic_block block = BASIC_BLOCK_FOR_FN (cfun, rpo[idx]);
-	    if (EDGE_COUNT (block->succs) >= 2)
-	      changed |= do_hoist_insertion (block);
-	  }
       for (int idx = 0; idx < rpo_num; ++idx)
 	{
 	  basic_block block = BASIC_BLOCK_FOR_FN (cfun, rpo[idx]);
@@ -3754,6 +3742,28 @@ insert (void)
 
   statistics_histogram_event (cfun, "insert iterations", num_iterations);
 
+  /* AVAIL_OUT is not needed after insertion so we don't have to
+     propagate NEW_SETS from hoist insertion.  */
+  FOR_ALL_BB_FN (bb, cfun)
+    {
+      bitmap_set_pool.remove (NEW_SETS (bb));
+      NEW_SETS (bb) = NULL;
+    }
+
+  /* Insert expressions for hoisting.  Do a backward walk here since
+     inserting into BLOCK exposes new opportunities in its predecessors.
+     Since PRE and hoist insertions can cause back-to-back iteration
+     and we are interested in PRE insertion exposed hoisting opportunities
+     but not in hoisting exposed PRE ones do hoist insertion only after
+     PRE insertion iteration finished and do not iterate it.  */
+  if (flag_code_hoisting)
+    for (int idx = rpo_num - 1; idx >= 0; --idx)
+      {
+	basic_block block = BASIC_BLOCK_FOR_FN (cfun, rpo[idx]);
+	if (EDGE_COUNT (block->succs) >= 2)
+	  changed |= do_hoist_insertion (block);
+      }
+
   free (rpo);
 }