[PATCH] Avoid compile time hog on vect_peel_nonlinear_iv_init for nonlinear induction vec_step_op_mul when iteration count is too big. 65;6800;1c There's loop in vect_peel_nonlinear_iv_init to get init_expr * pow (step_expr, skip_niters). When skipn_iters is too big, compile time hogs. To avoid that, optimize init_expr * pow (step_expr, skip_niters) to init_expr << (exact_log2 (step_expr) * skip_niters) when step_expr is pow of 2, otherwise give up vectorization when skip_niters >= TYPE_PRECISION (TREE_TYPE (init_expr)).

[liuhongt <hongtao.liu@intel.com>]

Also give up vectorization when niters_skip is negative which will be
used for fully masked loop.

Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
Ok for trunk?

gcc/ChangeLog:

	PR tree-optimization/111820
	PR tree-optimization/111833
	* tree-vect-loop-manip.cc (vect_can_peel_nonlinear_iv_p): Give
	up vectorization for nonlinear iv vect_step_op_mul when
	step_expr is not exact_log2 and niters is greater than
	TYPE_PRECISION (TREE_TYPE (step_expr)). Also don't vectorize
	for nagative niters_skip which will be used by fully masked
	loop.
	(vect_can_advance_ivs_p): Pass whole phi_info to
	vect_can_peel_nonlinear_iv_p.
	* tree-vect-loop.cc (vect_peel_nonlinear_iv_init): Optimize
	init_expr * pow (step_expr, skipn) to init_expr
	<< (log2 (step_expr) * skipn) when step_expr is exact_log2.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr111820-1.c: New test.
	* gcc.target/i386/pr111820-2.c: New test.
	* gcc.target/i386/pr103144-mul-1.c: Adjust testcase.
---
 .../gcc.target/i386/pr103144-mul-1.c          |  6 ++--
 gcc/testsuite/gcc.target/i386/pr111820-1.c    | 16 ++++++++++
 gcc/testsuite/gcc.target/i386/pr111820-2.c    | 17 ++++++++++
 gcc/tree-vect-loop-manip.cc                   | 28 ++++++++++++++--
 gcc/tree-vect-loop.cc                         | 32 ++++++++++++++++---
 5 files changed, 88 insertions(+), 11 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr111820-1.c
 create mode 100644 gcc/testsuite/gcc.target/i386/pr111820-2.c

diff --git a/gcc/testsuite/gcc.target/i386/pr103144-mul-1.c b/gcc/testsuite/gcc.target/i386/pr103144-mul-1.c
index 640c34fd959..f80d1094097 100644
--- a/gcc/testsuite/gcc.target/i386/pr103144-mul-1.c
+++ b/gcc/testsuite/gcc.target/i386/pr103144-mul-1.c
@@ -23,7 +23,7 @@ foo_mul_const (int* a)
   for (int i = 0; i != N; i++)
     {
       a[i] = b;
-      b *= 3;
+      b *= 4;
     }
 }
 
@@ -34,7 +34,7 @@ foo_mul_peel (int* a, int b)
   for (int i = 0; i != 39; i++)
     {
       a[i] = b;
-      b *= 3;
+      b *= 4;
     }
 }
 
@@ -46,6 +46,6 @@ foo_mul_peel_const (int* a)
   for (int i = 0; i != 39; i++)
     {
       a[i] = b;
-      b *= 3;
+      b *= 4;
     }
 }
diff --git a/gcc/testsuite/gcc.target/i386/pr111820-1.c b/gcc/testsuite/gcc.target/i386/pr111820-1.c
new file mode 100644
index 00000000000..50e960c39d4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr111820-1.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -mavx2 -fno-tree-vrp -Wno-aggressive-loop-optimizations -fdump-tree-vect-details" } */
+/* { dg-final { scan-tree-dump "Avoid compile time hog on vect_peel_nonlinear_iv_init for nonlinear induction vec_step_op_mul when iteration count is too big" "vect" } } */
+
+int r;
+int r_0;
+
+void f1 (void)
+{
+  int n = 0;
+  while (-- n)
+    {
+      r_0 += r;
+      r  *= 3;
+    }
+}
diff --git a/gcc/testsuite/gcc.target/i386/pr111820-2.c b/gcc/testsuite/gcc.target/i386/pr111820-2.c
new file mode 100644
index 00000000000..bbdb40798c6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr111820-2.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -mavx2 -fno-tree-vrp -fdump-tree-vect-details -Wno-aggressive-loop-optimizations" } */
+/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
+
+int r;
+int r_0;
+
+void f (void)
+{
+  int n = 0;
+  while (-- n)
+    {
+      r_0 += r ;
+      r  *= 2;
+    }
+}
+
diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 2608c286e5d..a530088b61d 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -1783,8 +1783,10 @@ iv_phi_p (stmt_vec_info stmt_info)
 /* Return true if vectorizer can peel for nonlinear iv.  */
 static bool
 vect_can_peel_nonlinear_iv_p (loop_vec_info loop_vinfo,
-			      enum vect_induction_op_type induction_type)
+			      stmt_vec_info stmt_info)
 {
+  enum vect_induction_op_type induction_type
+    = STMT_VINFO_LOOP_PHI_EVOLUTION_TYPE (stmt_info);
   tree niters_skip;
   /* Init_expr will be update by vect_update_ivs_after_vectorizer,
      if niters or vf is unkown:
@@ -1805,11 +1807,31 @@ vect_can_peel_nonlinear_iv_p (loop_vec_info loop_vinfo,
       return false;
     }
 
+  /* Avoid compile time hog on vect_peel_nonlinear_iv_init.  */
+  if (induction_type == vect_step_op_mul)
+    {
+      tree step_expr = STMT_VINFO_LOOP_PHI_EVOLUTION_PART (stmt_info);
+      tree type = TREE_TYPE (step_expr);
+
+      if (wi::exact_log2 (wi::to_wide (step_expr)) == -1
+	  && LOOP_VINFO_INT_NITERS(loop_vinfo) >= TYPE_PRECISION (type))
+	{
+	  if (dump_enabled_p ())
+	    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+			     "Avoid compile time hog on"
+			     " vect_peel_nonlinear_iv_init"
+			     " for nonlinear induction vec_step_op_mul"
+			     " when iteration count is too big.\n");
+	  return false;
+	}
+    }
+
   /* Also doens't support peel for neg when niter is variable.
      ??? generate something like niter_expr & 1 ? init_expr : -init_expr?  */
   niters_skip = LOOP_VINFO_MASK_SKIP_NITERS (loop_vinfo);
   if ((niters_skip != NULL_TREE
-       && TREE_CODE (niters_skip) != INTEGER_CST)
+       && (TREE_CODE (niters_skip) != INTEGER_CST
+	   || (HOST_WIDE_INT) TREE_INT_CST_LOW (niters_skip) < 0))
       || (!vect_use_loop_mask_for_alignment_p (loop_vinfo)
 	  && LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) < 0))
     {
@@ -1870,7 +1892,7 @@ vect_can_advance_ivs_p (loop_vec_info loop_vinfo)
       induction_type = STMT_VINFO_LOOP_PHI_EVOLUTION_TYPE (phi_info);
       if (induction_type != vect_step_op_add)
 	{
-	  if (!vect_can_peel_nonlinear_iv_p (loop_vinfo, induction_type))
+	  if (!vect_can_peel_nonlinear_iv_p (loop_vinfo, phi_info))
 	    return false;
 
 	  continue;
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 89bdcaa0910..6bb1f3dc462 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -9134,11 +9134,33 @@ vect_peel_nonlinear_iv_init (gimple_seq* stmts, tree init_expr,
 	init_expr = gimple_convert (stmts, utype, init_expr);
 	unsigned skipn = TREE_INT_CST_LOW (skip_niters);
 	wide_int begin = wi::to_wide (step_expr);
-	for (unsigned i = 0; i != skipn - 1; i++)
-	  begin = wi::mul (begin, wi::to_wide (step_expr));
-	tree mult_expr = wide_int_to_tree (utype, begin);
-	init_expr = gimple_build (stmts, MULT_EXPR, utype, init_expr, mult_expr);
-	init_expr = gimple_convert (stmts, type, init_expr);
+	int pow2_step = wi::exact_log2 (begin);
+	/* Optimize init_expr * pow (step_expr, skipn) to
+	   init_expr << (log2 (step_expr) * skipn).  */
+	if (pow2_step != -1)
+	  {
+	    if (skipn >= TYPE_PRECISION (type)
+		|| skipn > (UINT_MAX / (unsigned) pow2_step)
+		|| skipn * (unsigned) pow2_step >= TYPE_PRECISION (type))
+		init_expr = build_zero_cst (type);
+	    else
+	      {
+		tree lshc = build_int_cst (utype, skipn * (unsigned) pow2_step);
+		init_expr = gimple_build (stmts, LSHIFT_EXPR, utype,
+					  init_expr, lshc);
+	      }
+	  }
+	/* Any better way for init_expr * pow (step_expr, skipn)???.  */
+	else
+	  {
+	    gcc_assert (skipn < TYPE_PRECISION (type));
+	    for (unsigned i = 0; i != skipn - 1; i++)
+	      begin = wi::mul (begin, wi::to_wide (step_expr));
+	    tree mult_expr = wide_int_to_tree (utype, begin);
+	    init_expr = gimple_build (stmts, MULT_EXPR, utype,
+				      init_expr, mult_expr);
+	  }
+	  init_expr = gimple_convert (stmts, type, init_expr);
       }
       break;
 
-- 
2.31.1