gimple-ssa-strength-reduction.c (lookup_cand): Adjust index by 1.

	* gimple-ssa-strength-reduction.c (lookup_cand): Adjust index by 1.
	(alloc_cand_and_find_basis): Ditto.
	(backtrace_base_for_ref, create_mul_ssa_cand): Remove if-then-else.
	(create_mul_imm_cand, create_add_ssa_cand): Ditto.
	(create_add_imm_cand, slsr_process_cast): Ditto.
	(slsr_process_copy, replace_mult_candidate): Ditto.
	(replace_rhs_if_not_dup, replace_one_candidate): Ditto.
	(dump_cand_vec, analyze_candidates_and_replace): Skip NULL element.
	(pass_strength_reduction::execute): Init the first NULL element.

From-SVN: r271145

gcc/ChangeLog

+2019-05-14  Bin Cheng  <bin.cheng@linux.alibaba.com>
+
+	* gimple-ssa-strength-reduction.c (lookup_cand): Adjust index by 1.
+	(alloc_cand_and_find_basis): Ditto.
+	(backtrace_base_for_ref, create_mul_ssa_cand): Remove if-then-else.
+	(create_mul_imm_cand, create_add_ssa_cand): Ditto.
+	(create_add_imm_cand, slsr_process_cast): Ditto.
+	(slsr_process_copy, replace_mult_candidate): Ditto.
+	(replace_rhs_if_not_dup, replace_one_candidate): Ditto.
+	(dump_cand_vec, analyze_candidates_and_replace): Skip NULL element.
+	(pass_strength_reduction::execute): Init the first NULL element.
+
 2019-05-13  Nathan Sidwell  <nathan@acm.org>
 
 	* gcc.c (execute): Simplify cond-expr into if.  Reformat comment.

gcc/gimple-ssa-strength-reduction.c

@@ -418,7 +418,7 @@ static bool legal_cast_p_1 (tree, tree);
 static slsr_cand_t
 lookup_cand (cand_idx idx)
 {
-  return cand_vec[idx - 1];
+  return cand_vec[idx];
 }
 
 /* Helper for hashing a candidate chain header.  */
@@ -688,7 +688,7 @@ alloc_cand_and_find_basis (enum cand_kind kind, gimple *gs, tree base,
   c->cand_type = ctype;
   c->stride_type = stype;
   c->kind = kind;
-  c->cand_num = cand_vec.length () + 1;
+  c->cand_num = cand_vec.length ();
   c->next_interp = 0;
   c->first_interp = c->cand_num;
   c->dependent = 0;
@@ -933,10 +933,7 @@ backtrace_base_for_ref (tree *pbase)
 	  return base_cand->index;
 	}
 
-      if (base_cand->next_interp)
       base_cand = lookup_cand (base_cand->next_interp);
-      else
-	base_cand = NULL;
     }
 
   return 0;
@@ -1124,10 +1121,7 @@ create_mul_ssa_cand (gimple *gs, tree base_in, tree stride_in, bool speed)
 		       + stmt_cost (base_cand->cand_stmt, speed));
 	}
 
-      if (base_cand->next_interp)
       base_cand = lookup_cand (base_cand->next_interp);
-      else
-	base_cand = NULL;
     }
 
   if (!base)
@@ -1214,10 +1208,7 @@ create_mul_imm_cand (gimple *gs, tree base_in, tree stride_in, bool speed)
 		       + stmt_cost (base_cand->cand_stmt, speed));
 	}
 
-      if (base_cand->next_interp)
       base_cand = lookup_cand (base_cand->next_interp);
-      else
-	base_cand = NULL;
     }
 
   if (!base)
@@ -1320,10 +1311,7 @@ create_add_ssa_cand (gimple *gs, tree base_in, tree addend_in,
 		       + stmt_cost (addend_cand->cand_stmt, speed));
 	}
 
-      if (addend_cand->next_interp)
       addend_cand = lookup_cand (addend_cand->next_interp);
-      else
-	addend_cand = NULL;
     }
 
   while (base_cand && !base && base_cand->kind != CAND_PHI)
@@ -1372,17 +1360,11 @@ create_add_ssa_cand (gimple *gs, tree base_in, tree addend_in,
 			       + stmt_cost (subtrahend_cand->cand_stmt, speed));
 		}
 
-	      if (subtrahend_cand->next_interp)
 	      subtrahend_cand = lookup_cand (subtrahend_cand->next_interp);
-	      else
-		subtrahend_cand = NULL;
 	    }
 	}
       
-      if (base_cand->next_interp)
       base_cand = lookup_cand (base_cand->next_interp);
-      else
-	base_cand = NULL;
     }
 
   if (!base)
@@ -1446,10 +1428,7 @@ create_add_imm_cand (gimple *gs, tree base_in, const widest_int &index_in,
 		       + stmt_cost (base_cand->cand_stmt, speed));
 	}
 
-      if (base_cand->next_interp)
       base_cand = lookup_cand (base_cand->next_interp);
-      else
-	base_cand = NULL;
     }
 
   if (!base)
@@ -1652,10 +1631,7 @@ slsr_process_cast (gimple *gs, tree rhs1, bool speed)
 	  if (first_cand != c)
 	    c->first_interp = first_cand->cand_num;
 
-	  if (base_cand->next_interp)
 	  base_cand = lookup_cand (base_cand->next_interp);
-	  else
-	    base_cand = NULL;
 	}
     }
   else 
@@ -1719,10 +1695,7 @@ slsr_process_copy (gimple *gs, tree rhs1, bool speed)
 	  if (first_cand != c)
 	    c->first_interp = first_cand->cand_num;
 
-	  if (base_cand->next_interp)
 	  base_cand = lookup_cand (base_cand->next_interp);
-	  else
-	    base_cand = NULL;
 	}
     }
   else 
@@ -1933,6 +1906,7 @@ dump_cand_vec (void)
   fprintf (dump_file, "\nStrength reduction candidate vector:\n\n");
   
   FOR_EACH_VEC_ELT (cand_vec, i, c)
+    if (c != NULL)
       dump_candidate (c);
 }
 
@@ -2181,7 +2155,7 @@ replace_mult_candidate (slsr_cand_t c, tree basis_name, widest_int bump)
       while (cc)
 	{
 	  cc->cand_stmt = copy_stmt;
-	  cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
+	  cc = lookup_cand (cc->next_interp);
 	}
       if (dump_file && (dump_flags & TDF_DETAILS))
 	stmt_to_print = copy_stmt;
@@ -2214,7 +2188,7 @@ replace_mult_candidate (slsr_cand_t c, tree basis_name, widest_int bump)
 	  while (cc)
 	    {
 	      cc->cand_stmt = gsi_stmt (gsi);
-	      cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
+	      cc = lookup_cand (cc->next_interp);
 	    }
 	  if (dump_file && (dump_flags & TDF_DETAILS))
 	    stmt_to_print = gsi_stmt (gsi);
@@ -3654,7 +3628,7 @@ replace_rhs_if_not_dup (enum tree_code new_code, tree new_rhs1, tree new_rhs2,
       while (cc)
 	{
 	  cc->cand_stmt = gsi_stmt (gsi);
-	  cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
+	  cc = lookup_cand (cc->next_interp);
 	}
 
       if (dump_file && (dump_flags & TDF_DETAILS))
@@ -3770,7 +3744,7 @@ replace_one_candidate (slsr_cand_t c, unsigned i, tree basis_name)
 	  while (cc)
 	    {
 	      cc->cand_stmt = gsi_stmt (gsi);
-	      cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
+	      cc = lookup_cand (cc->next_interp);
 	    }
 
 	  if (dump_file && (dump_flags & TDF_DETAILS))
@@ -3796,7 +3770,7 @@ replace_one_candidate (slsr_cand_t c, unsigned i, tree basis_name)
 	  while (cc)
 	    {
 	      cc->cand_stmt = copy_stmt;
-	      cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
+	      cc = lookup_cand (cc->next_interp);
 	    }
 
 	  if (dump_file && (dump_flags & TDF_DETAILS))
@@ -3812,7 +3786,7 @@ replace_one_candidate (slsr_cand_t c, unsigned i, tree basis_name)
 	  while (cc)
 	    {
 	      cc->cand_stmt = cast_stmt;
-	      cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
+	      cc = lookup_cand (cc->next_interp);
 	    }
 
 	  if (dump_file && (dump_flags & TDF_DETAILS))
@@ -3902,8 +3876,10 @@ analyze_candidates_and_replace (void)
   /* Each candidate that has a null basis and a non-null
      dependent is the root of a tree of related statements.
      Analyze each tree to determine a subset of those
-     statements that can be replaced with maximum benefit.  */
-  FOR_EACH_VEC_ELT (cand_vec, i, c)
+     statements that can be replaced with maximum benefit.
+
+     Note the first NULL element is skipped.  */
+  FOR_EACH_VEC_ELT_FROM (cand_vec, i, c, 1)
     {
       slsr_cand_t first_dep;
 
@@ -4010,8 +3986,9 @@ pass_strength_reduction::execute (function *fun)
   /* Create the obstack where candidates will reside.  */
   gcc_obstack_init (&cand_obstack);
 
-  /* Allocate the candidate vector.  */
+  /* Allocate the candidate vector and initialize the first NULL element.  */
   cand_vec.create (128);
+  cand_vec.safe_push (NULL);
 
   /* Allocate the mapping from statements to candidate indices.  */
   stmt_cand_map = new hash_map<gimple *, slsr_cand_t>;