Avoid compile time hog on vect_peel_nonlinear_iv_init for nonlinear induction vec_step_op_mul when iteration count is too big.

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)).

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

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/pr111820-3.c: New test.
	* gcc.target/i386/pr103144-mul-1.c: Adjust testcase.
	* gcc.target/i386/pr103144-mul-2.c: Adjust testcase.

gcc/testsuite/gcc.target/i386/pr103144-mul-1.c

@@ -11,7 +11,7 @@ foo_mul (int* a, int b)
   for (int i = 0; i != N; i++)
     {
       a[i] = b;
-      b *= 3;
+      b *= 4;
     }
 }
 
@@ -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;
     }
 }

gcc/testsuite/gcc.target/i386/pr103144-mul-2.c

@@ -16,12 +16,12 @@ avx2_test (void)
 
   __builtin_memset (epi32_exp, 0, N * sizeof (int));
   int b = 8;
-  v8si init = __extension__(v8si) { b, b * 3, b * 9, b * 27, b * 81, b * 243, b * 729, b * 2187 };
+  v8si init = __extension__(v8si) { b, b * 4, b * 16, b * 64, b * 256, b * 1024, b * 4096, b * 16384 };
 
   for (int i = 0; i != N / 8; i++)
     {
       memcpy (epi32_exp + i * 8, &init, 32);
-      init *= 6561;
+      init *= 65536;
     }
 
   foo_mul (epi32_dst, b);
@@ -32,11 +32,11 @@ avx2_test (void)
   if (__builtin_memcmp (epi32_dst, epi32_exp, 39 * 4) != 0)
     __builtin_abort ();
 
-  init = __extension__(v8si) { 1, 3, 9, 27, 81, 243, 729, 2187 };
+  init = __extension__(v8si) { 1, 4, 16, 64, 256, 1024, 4096, 16384 };
   for (int i = 0; i != N / 8; i++)
     {
       memcpy (epi32_exp + i * 8, &init, 32);
-      init *= 6561;
+      init *= 65536;
     }
 
   foo_mul_const (epi32_dst);

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;
+    }
+}

gcc/testsuite/gcc.target/i386/pr111820-2.c

@@ -0,0 +1,16 @@
+/* { 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;
+    }
+}

gcc/testsuite/gcc.target/i386/pr111820-3.c

@@ -0,0 +1,16 @@
+/* { 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 = 14;
+  while (-- n)
+    {
+      r_0 += r ;
+      r  *= 3;
+    }
+}

gcc/tree-vect-loop-manip.cc

@@ -1904,8 +1904,10 @@ 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:
@@ -1926,11 +1928,31 @@ 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))
     {
@@ -1991,7 +2013,7 @@ 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;

gcc/tree-vect-loop.cc

@@ -9222,12 +9222,17 @@ vect_peel_nonlinear_iv_init (gimple_seq* stmts, tree init_expr,
       {
 	tree utype = unsigned_type_for (type);
 	init_expr = gimple_convert (stmts, utype, init_expr);
-	unsigned skipn = TREE_INT_CST_LOW (skip_niters);
+	wide_int skipn = wi::to_wide (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));
+	auto_mpz base, exp, mod, res;
+	wi::to_mpz (begin, base, TYPE_SIGN (type));
+	wi::to_mpz (skipn, exp, UNSIGNED);
+	mpz_ui_pow_ui (mod, 2, TYPE_PRECISION (type));
+	mpz_powm (res, base, exp, mod);
+	begin = wi::from_mpz (type, res, TYPE_SIGN (type));
 	tree mult_expr = wide_int_to_tree (utype, begin);
-	init_expr = gimple_build (stmts, MULT_EXPR, utype, init_expr, mult_expr);
+	init_expr = gimple_build (stmts, MULT_EXPR, utype,
+				  init_expr, mult_expr);
 	init_expr = gimple_convert (stmts, type, init_expr);
       }
       break;