re PR middle-end/81889 (bogus warnings with -Wmaybe-uninitialized -O3)

2017-12-12  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/81889
	* tree-ssa-loop-niter.c (infer_loop_bounds_from_signedness): Use
	range info from the non-wrapping IV instead of just the range
	of the type.

	* gfortran.dg/pr81889.f90: New testcase.
	* gcc.dg/tree-ssa/pr64183.c: Adjust.

From-SVN: r255573

gcc/ChangeLog

+2017-12-12  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/81889
+	* tree-ssa-loop-niter.c (infer_loop_bounds_from_signedness): Use
+	range info from the non-wrapping IV instead of just the range
+	of the type.
+
 2017-12-12  Julia Koval  <julia.koval@intel.com>
 
 	* config.gcc: Add vaesintrin.h.

gcc/testsuite/ChangeLog

+2017-12-12  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/81889
+	* gfortran.dg/pr81889.f90: New testcase.
+	* gcc.dg/tree-ssa/pr64183.c: Adjust.
+
 2017-12-12  Julia Koval  <julia.koval@intel.com>
 
 	* gcc.target/i386/avx512-check.h: Handle bit_VAES.

gcc/testsuite/gcc.dg/tree-ssa/pr64183.c

@@ -17,4 +17,4 @@ test ()
    bits += 8;
 }
 
-/* { dg-final { scan-tree-dump "Loop 2 iterates at most 4 times" "cunroll"} } */
+/* { dg-final { scan-tree-dump "Loop 2 iterates at most 3 times" "cunroll"} } */

gcc/testsuite/gfortran.dg/pr81889.f90

+! { dg-do compile }
+! { dg-options "-O3 -Wall" }
+
+module m
+
+   type t
+      integer, dimension(:), pointer :: list
+   end type
+
+contains
+
+   subroutine s(n, p, Y)
+      integer, intent(in) :: n
+      type(t) :: p
+      real, dimension(:) :: Y
+
+      real, dimension(1:16) :: xx
+
+      if (n > 3) then
+         xx(1:n) = 0.
+         print *, xx(1:n)
+      else
+         xx(1:n) = Y(p%list(1:n)) ! { dg-bogus "uninitialized" }
+         print *, sum(xx(1:n))
+      end if
+
+   end subroutine
+
+end module

gcc/tree-ssa-loop-niter.c

@@ -3510,6 +3510,12 @@ infer_loop_bounds_from_signedness (struct loop *loop, gimple *stmt)
 
   low = lower_bound_in_type (type, type);
   high = upper_bound_in_type (type, type);
+  wide_int minv, maxv;
+  if (get_range_info (def, &minv, &maxv) == VR_RANGE)
+    {
+      low = wide_int_to_tree (type, minv);
+      high = wide_int_to_tree (type, maxv);
+    }
 
   record_nonwrapping_iv (loop, base, step, stmt, low, high, false, true);
 }