Simplify loop size when step=1

2019-06-04  Marc Glisse  <marc.glisse@inria.fr>

	* tree-ssa-loop-niter.c (number_of_iterations_ne): Skip
	computations when step is 1.

From-SVN: r271926

gcc/ChangeLog

+2019-06-04  Marc Glisse  <marc.glisse@inria.fr>
+
+	* tree-ssa-loop-niter.c (number_of_iterations_ne): Skip
+	computations when step is 1.
+
 2019-06-04  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/rs6000/constraints.md (define_register_constraint "wf"):

gcc/tree-ssa-loop-niter.c

@@ -1125,8 +1125,15 @@ number_of_iterations_ne (struct loop *loop, tree type, affine_iv *iv,
     }
 
   c = fold_build2 (EXACT_DIV_EXPR, niter_type, c, d);
-  tmp = fold_build2 (MULT_EXPR, niter_type, c, inverse (s, bound));
-  niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
+  if (integer_onep (s))
+    {
+      niter->niter = c;
+    }
+  else
+    {
+      tmp = fold_build2 (MULT_EXPR, niter_type, c, inverse (s, bound));
+      niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
+    }
   return true;
 }