tree-ssa-loop-niter.c (number_of_iterations_lt_to_ne): Clean up by removing computation of may_be_zero.

	* tree-ssa-loop-niter.c (number_of_iterations_lt_to_ne): Clean up
	by removing computation of may_be_zero.

From-SVN: r238585

1 files changed, 28 insertions, 77 deletions

diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index d96c03b..1102c8a 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -1072,12 +1072,8 @@ number_of_iterations_lt_to_ne (tree type, affine_iv *iv0, affine_iv *iv1,
   tree niter_type = TREE_TYPE (step);
   tree mod = fold_build2 (FLOOR_MOD_EXPR, niter_type, *delta, step);
   tree tmod;
-  mpz_t mmod;
-  tree assumption = boolean_true_node, bound, noloop;
-  bool ret = false, fv_comp_no_overflow;
-  tree type1 = type;
-  if (POINTER_TYPE_P (type))
-    type1 = sizetype;
+  tree assumption = boolean_true_node, bound;
+  tree type1 = (POINTER_TYPE_P (type)) ? sizetype : type;
 
   if (TREE_CODE (mod) != INTEGER_CST)
     return false;
@@ -1085,96 +1081,51 @@ number_of_iterations_lt_to_ne (tree type, affine_iv *iv0, affine_iv *iv1,
     mod = fold_build2 (MINUS_EXPR, niter_type, step, mod);
   tmod = fold_convert (type1, mod);
 
-  mpz_init (mmod);
-  wi::to_mpz (mod, mmod, UNSIGNED);
-  mpz_neg (mmod, mmod);
-
   /* If the induction variable does not overflow and the exit is taken,
-     then the computation of the final value does not overflow.  This is
-     also obviously the case if the new final value is equal to the
-     current one.  Finally, we postulate this for pointer type variables,
-     as the code cannot rely on the object to that the pointer points being
-     placed at the end of the address space (and more pragmatically,
-     TYPE_{MIN,MAX}_VALUE is not defined for pointers).  */
-  if (integer_zerop (mod) || POINTER_TYPE_P (type))
-    fv_comp_no_overflow = true;
-  else if (!exit_must_be_taken)
-    fv_comp_no_overflow = false;
-  else
-    fv_comp_no_overflow =
-	    (iv0->no_overflow && integer_nonzerop (iv0->step))
-	    || (iv1->no_overflow && integer_nonzerop (iv1->step));
-
-  if (integer_nonzerop (iv0->step))
+     then the computation of the final value does not overflow.  There
+     are three cases:
+       1) The case if the new final value is equal to the current one.
+       2) Induction varaible has pointer type, as the code cannot rely
+	  on the object to that the pointer points being placed at the
+	  end of the address space (and more pragmatically,
+	  TYPE_{MIN,MAX}_VALUE is not defined for pointers).
+       3) EXIT_MUST_BE_TAKEN is true, note it implies that the induction
+	  variable does not overflow.  */
+  if (!integer_zerop (mod) && !POINTER_TYPE_P (type) && !exit_must_be_taken)
     {
-      /* The final value of the iv is iv1->base + MOD, assuming that this
-	 computation does not overflow, and that
-	 iv0->base <= iv1->base + MOD.  */
-      if (!fv_comp_no_overflow)
+      if (integer_nonzerop (iv0->step))
 	{
+	  /* The final value of the iv is iv1->base + MOD, assuming
+	     that this computation does not overflow, and that
+	     iv0->base <= iv1->base + MOD.  */
 	  bound = fold_build2 (MINUS_EXPR, type1,
 			       TYPE_MAX_VALUE (type1), tmod);
 	  assumption = fold_build2 (LE_EXPR, boolean_type_node,
 				    iv1->base, bound);
-	  if (integer_zerop (assumption))
-	    goto end;
 	}
-      if (mpz_cmp (mmod, bnds->below) < 0)
-	noloop = boolean_false_node;
-      else if (POINTER_TYPE_P (type))
-	noloop = fold_build2 (GT_EXPR, boolean_type_node,
-			      iv0->base,
-			      fold_build_pointer_plus (iv1->base, tmod));
       else
-	noloop = fold_build2 (GT_EXPR, boolean_type_node,
-			      iv0->base,
-			      fold_build2 (PLUS_EXPR, type1,
-					   iv1->base, tmod));
-    }
-  else
-    {
-      /* The final value of the iv is iv0->base - MOD, assuming that this
-	 computation does not overflow, and that
-	 iv0->base - MOD <= iv1->base. */
-      if (!fv_comp_no_overflow)
 	{
+	  /* The final value of the iv is iv0->base - MOD, assuming
+	     that this computation does not overflow, and that
+	     iv0->base - MOD <= iv1->base.  */
 	  bound = fold_build2 (PLUS_EXPR, type1,
 			       TYPE_MIN_VALUE (type1), tmod);
 	  assumption = fold_build2 (GE_EXPR, boolean_type_node,
 				    iv0->base, bound);
-	  if (integer_zerop (assumption))
-	    goto end;
 	}
-      if (mpz_cmp (mmod, bnds->below) < 0)
-	noloop = boolean_false_node;
-      else if (POINTER_TYPE_P (type))
-	noloop = fold_build2 (GT_EXPR, boolean_type_node,
-			      fold_build_pointer_plus (iv0->base,
-						       fold_build1 (NEGATE_EXPR,
-								    type1, tmod)),
-			      iv1->base);
-      else
-	noloop = fold_build2 (GT_EXPR, boolean_type_node,
-			      fold_build2 (MINUS_EXPR, type1,
-					   iv0->base, tmod),
-			      iv1->base);
+      if (integer_zerop (assumption))
+	return false;
+      else if (!integer_nonzerop (assumption))
+	niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+					  niter->assumptions, assumption);
     }
 
-  if (!integer_nonzerop (assumption))
-    niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
-				      niter->assumptions,
-				      assumption);
-  if (!integer_zerop (noloop))
-    niter->may_be_zero = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
-				      niter->may_be_zero,
-				      noloop);
+  /* Since we are transforming LT to NE and DELTA is constant, there
+     is no need to compute may_be_zero because this loop must roll.  */
+
   bounds_add (bnds, wi::to_widest (mod), type);
   *delta = fold_build2 (PLUS_EXPR, niter_type, *delta, mod);
-
-  ret = true;
-end:
-  mpz_clear (mmod);
-  return ret;
+  return true;
 }
 
 /* Add assertions to NITER that ensure that the control variable of the loop