Loop split on semi-invariant conditional statement

2019-11-07  Feng Xue <fxue@os.amperecomputing.com>

        PR tree-optimization/89134
        * doc/invoke.texi (min-loop-cond-split-prob): Document new --params.
        * params.def: Add min-loop-cond-split-prob.
        * tree-ssa-loop-split.c (split_loop): Remove niter parameter, move some
        outside checks on loop into the function.
        (split_info): New class.
        (find_vdef_in_loop, get_control_equiv_head_block): New functions.
        (find_control_dep_blocks, vuse_semi_invariant_p): Likewise.
        (ssa_semi_invariant_p, loop_iter_phi_semi_invariant_p): Likewise.
        (control_dep_semi_invariant_p, stmt_semi_invariant_p_1): Likewise.
        (stmt_semi_invariant_p, branch_removable_p): Likewise.
        (get_cond_invariant_branch, compute_added_num_insns): Likewise.
        (get_cond_branch_to_split_loop, do_split_loop_on_cond): Likewise.
        (split_loop_on_cond): Likewise.
        (tree_ssa_split_loops): Add loop split on conditional statement.

2019-11-07  Feng Xue  <fxue@os.amperecomputing.com>

        PR tree-optimization/89134
        * gcc.dg/tree-ssa/loop-cond-split-1.c: New test.
        * g++.dg/tree-ssa/loop-cond-split-1.C: New test.
        * gcc.dg/torture/pr55107.c: Add -fno-split-loops.

From-SVN: r277923

gcc/ChangeLog

@@ -1,3 +1,21 @@
+2019-11-07  Feng Xue <fxue@os.amperecomputing.com>
+
+	PR tree-optimization/89134
+	* doc/invoke.texi (min-loop-cond-split-prob): Document new --params.
+	* params.def: Add min-loop-cond-split-prob.
+	* tree-ssa-loop-split.c (split_loop): Remove niter parameter, move some
+	outside checks on loop into the function.
+	(split_info): New class.
+	(find_vdef_in_loop, get_control_equiv_head_block): New functions.
+	(find_control_dep_blocks, vuse_semi_invariant_p): Likewise.
+	(ssa_semi_invariant_p, loop_iter_phi_semi_invariant_p): Likewise.
+	(control_dep_semi_invariant_p, stmt_semi_invariant_p_1): Likewise.
+	(stmt_semi_invariant_p, branch_removable_p): Likewise.
+	(get_cond_invariant_branch, compute_added_num_insns): Likewise.
+	(get_cond_branch_to_split_loop, do_split_loop_on_cond): Likewise.
+	(split_loop_on_cond): Likewise.
+	(tree_ssa_split_loops): Add loop split on conditional statement.
+
 2019-11-07  Andreas Krebbel  <krebbel@linux.ibm.com>
 
 	* config/s390/s390.md ("*cstorecc<mode>_z13"): New insn_and_split

gcc/doc/invoke.texi

@@ -11517,6 +11517,11 @@ The maximum number of branches unswitched in a single loop.
 @item lim-expensive
 The minimum cost of an expensive expression in the loop invariant motion.
 
+@item min-loop-cond-split-prob
+When FDO profile information is available, @option{min-loop-cond-split-prob}
+specifies minimum threshold for probability of semi-invariant condition
+statement to trigger loop split.
+
 @item iv-consider-all-candidates-bound
 Bound on number of candidates for induction variables, below which
 all candidates are considered for each use in induction variable

gcc/params.def

@@ -415,6 +415,12 @@ DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
 	"The maximum number of unswitchings in a single loop.",
 	3, 0, 0)
 
+DEFPARAM(PARAM_MIN_LOOP_COND_SPLIT_PROB,
+	"min-loop-cond-split-prob",
+	"The minimum threshold for probability of semi-invariant condition "
+	"statement to trigger loop split.",
+	30, 0, 100)
+
 /* The maximum number of insns in loop header duplicated by the copy loop
    headers pass.  */
 DEFPARAM(PARAM_MAX_LOOP_HEADER_INSNS,

gcc/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2019-11-07  Feng Xue  <fxue@os.amperecomputing.com>
+
+	PR tree-optimization/89134
+	* gcc.dg/tree-ssa/loop-cond-split-1.c: New test.
+	* g++.dg/tree-ssa/loop-cond-split-1.C: New test.
+	* gcc.dg/torture/pr55107.c: Add -fno-split-loops.
+
 2019-11-07  Andreas Krebbel  <krebbel@linux.ibm.com>
 
 	* gcc.target/s390/addsub-signed-overflow-1.c: Expect lochi

gcc/testsuite/g++.dg/tree-ssa/loop-cond-split-1.C

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-lsplit-details" } */
+
+#include <string>
+#include <map>
+
+using namespace std;
+
+class  A
+{
+public:
+  bool empty;
+  void set (string s);
+};
+
+class  B
+{
+  map<int, string> m;
+  void f ();
+};
+
+extern A *ga;
+
+void B::f ()
+{
+  for (map<int, string>::iterator iter = m.begin (); iter != m.end (); ++iter)
+    {
+      if (ga->empty)
+        ga->set (iter->second);
+    }
+}
+
+/* { dg-final { scan-tree-dump-times "loop split on semi-invariant condition at false branch" 1 "lsplit" } } */

gcc/testsuite/gcc.dg/torture/pr55107.c

@@ -1,4 +1,5 @@
 /* { dg-do compile } */
+/* { dg-additional-options "-fno-split-loops" } */
 
 typedef unsigned short uint16_t;
 

gcc/testsuite/gcc.dg/tree-ssa/loop-cond-split-1.c

@@ -0,0 +1,97 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-lsplit-details" } */
+
+extern const int step;
+
+int ga, gb;
+
+__attribute__((pure)) __attribute__((noinline)) int inc (int i)
+{
+  return i + step;
+}
+
+extern int do_something (void);
+
+void test1 (int n)
+{
+  int i;
+
+  for (i = 0; i < n; i = inc (i))
+    {
+      if (ga)
+        ga = do_something ();
+    }
+}
+
+void test2 (int n, int p)
+{
+  int i;
+  int v;
+
+  for (i = 0; i < n ; i = inc (i))
+    {
+      if (ga)
+       {
+         v = inc (2);
+         gb += 1;
+       }
+      else
+       {
+         v = p * p;
+         gb *= 3;
+       }
+
+      if (v < 10)
+        ga = do_something ();
+    }
+}
+
+void test3 (int n, int p)
+{
+  int i;
+  int c = p + 1;
+  int v;
+
+  for (i = 0; i < n ; i = inc (i))
+    {
+      if (c)
+       {
+         v = inc (c);
+         gb += 1;
+       }
+      else
+       {
+         v = p * p;
+         gb *= 3;
+       }
+
+      if (v < 10)
+        c = do_something ();
+    }
+}
+
+void test4 (int n, int p)
+{
+  int i;
+  int v;
+
+  for (i = 0; i < n ; i = inc (i))
+    {
+      if (ga)
+       {
+         v = inc (2);
+         if (gb > 16)
+           v = inc (5);  
+       }
+      else
+       {
+         v = p * p;
+         gb += 2;
+       }
+
+      if (v < 10)
+        ga = do_something ();
+    }
+}
+
+/* { dg-final { scan-tree-dump-times "loop split on semi-invariant condition at false branch" 3 "lsplit" } } */