re PR tree-optimization/90356 (Missed optimization for variables initialized to 0.0)

	PR tree-optimization/90356
	* match.pd ((X +/- 0.0) +/- 0.0): Optimize into X +/- 0.0 if possible.

	* gcc.dg/tree-ssa/pr90356-1.c: New test.
	* gcc.dg/tree-ssa/pr90356-2.c: New test.
	* gcc.dg/tree-ssa/pr90356-3.c: New test.
	* gcc.dg/tree-ssa/pr90356-4.c: New test.

From-SVN: r271001

gcc/ChangeLog

+2019-05-08  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/90356
+	* match.pd ((X +/- 0.0) +/- 0.0): Optimize into X +/- 0.0 if possible.
+
 2019-05-07  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/rs6000/rs6000-protos.h (rs6000_legitimize_reload_address_ptr):

gcc/match.pd

@@ -152,6 +152,28 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  (if (fold_real_zero_addition_p (type, @1, 1))
   (non_lvalue @0)))
 
+/* Even if the fold_real_zero_addition_p can't simplify X + 0.0
+   into X, we can optimize (X + 0.0) + 0.0 or (X + 0.0) - 0.0
+   or (X - 0.0) + 0.0 into X + 0.0 and (X - 0.0) - 0.0 into X - 0.0
+   if not -frounding-math.  For sNaNs the first operation would raise
+   exceptions but turn the result into qNan, so the second operation
+   would not raise it.   */
+(for inner_op (plus minus)
+ (for outer_op (plus minus)
+  (simplify
+   (outer_op (inner_op@3 @0 REAL_CST@1) REAL_CST@2)
+    (if (real_zerop (@1)
+	 && real_zerop (@2)
+	 && !HONOR_SIGN_DEPENDENT_ROUNDING (type))
+     (with { bool inner_plus = ((inner_op == PLUS_EXPR)
+				^ REAL_VALUE_MINUS_ZERO (TREE_REAL_CST (@1)));
+	     bool outer_plus
+	       = ((outer_op == PLUS_EXPR)
+		  ^ REAL_VALUE_MINUS_ZERO (TREE_REAL_CST (@2))); }
+      (if (outer_plus && !inner_plus)
+       (outer_op @0 @2)
+       @3))))))
+
 /* Simplify x - x.
    This is unsafe for certain floats even in non-IEEE formats.
    In IEEE, it is unsafe because it does wrong for NaNs.

gcc/testsuite/ChangeLog

+2019-05-08  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/90356
+	* gcc.dg/tree-ssa/pr90356-1.c: New test.
+	* gcc.dg/tree-ssa/pr90356-2.c: New test.
+	* gcc.dg/tree-ssa/pr90356-3.c: New test.
+	* gcc.dg/tree-ssa/pr90356-4.c: New test.
+
 2019-05-07  Cherry Zhang  <cherryyz@google.com>
 
 	* go.dg/arrayclear.go: New test.

gcc/testsuite/gcc.dg/tree-ssa/pr90356-1.c

+/* PR tree-optimization/90356 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-rounding-math -fsignaling-nans -fsigned-zeros -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "x_\[0-9]*.D. \\+ 0.0;" 12 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "y_\[0-9]*.D. - 0.0;" 4 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " \[+-] 0.0;" 16 "optimized" } } */
+
+double f1 (double x) { return (x + 0.0) + 0.0; }
+double f2 (double y) { return (y + (-0.0)) + (-0.0); }
+double f3 (double y) { return (y - 0.0) - 0.0; }
+double f4 (double x) { return (x - (-0.0)) - (-0.0); }
+double f5 (double x) { return (x + 0.0) - 0.0; }
+double f6 (double x) { return (x + (-0.0)) - (-0.0); }
+double f7 (double x) { return (x - 0.0) + 0.0; }
+double f8 (double x) { return (x - (-0.0)) + (-0.0); }
+double f9 (double x) { double t = x + 0.0; return t + 0.0; }
+double f10 (double y) { double t = y + (-0.0); return t + (-0.0); }
+double f11 (double y) { double t = y - 0.0; return t - 0.0; }
+double f12 (double x) { double t = x - (-0.0); return t - (-0.0); }
+double f13 (double x) { double t = x + 0.0; return t - 0.0; }
+double f14 (double x) { double t = x + (-0.0); return t - (-0.0); }
+double f15 (double x) { double t = x - 0.0; return t + 0.0; }
+double f16 (double x) { double t = x - (-0.0); return t + (-0.0); }

gcc/testsuite/gcc.dg/tree-ssa/pr90356-2.c

+/* PR tree-optimization/90356 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-rounding-math -fno-signaling-nans -fsigned-zeros -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "x_\[0-9]*.D. \\+ 0.0;" 12 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "y_\[0-9]*.D. - 0.0;" 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " \[+-] 0.0;" 12 "optimized" } } */
+
+#include "pr90356-1.c"

gcc/testsuite/gcc.dg/tree-ssa/pr90356-3.c

+/* PR tree-optimization/90356 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -frounding-math -fsignaling-nans -fsigned-zeros -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times " \[+-] 0.0;" 32 "optimized" } } */
+
+#include "pr90356-1.c"

gcc/testsuite/gcc.dg/tree-ssa/pr90356-4.c

+/* PR tree-optimization/90356 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -frounding-math -fno-signaling-nans -fsigned-zeros -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times " \[+-] 0.0;" 32 "optimized" } } */
+
+#include "pr90356-1.c"