re PR middle-end/57073 (__builtin_powif (-1.0, k) should be optimized to "1.0 - 2.0 * (K%2)")

2013-05-30  Tobias Burnus  <burnus@net-b.de>
            Thomas Koenig  <tkoenig@gcc.gnu.org>

        PR middle-end/57073
        * tree-ssa-math-opts.c (execute_cse_sincos): Optimize
        powi (-1.0, k) to (k & 1) ? -1.0 : 1.0.

2013-05-30  Tobias Burnus  <burnus@net-b.de>

        PR middle-end/57073
        * gfortran.dg/power_6.f90: New.

From-SVN: r199461

gcc/ChangeLog

+2013-05-30  Tobias Burnus  <burnus@net-b.de>
+	    Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR middle-end/57073
+	* tree-ssa-math-opts.c (execute_cse_sincos): Optimize
+	powi (-1.0, k) to (k & 1) ? -1.0 : 1.0.
+
 2013-05-30  Steven Bosscher  <steven@gcc.gnu.org>
 
-       * rtlanal.c (tablejump_p): Expect table and label to be adjacent.
+	* rtlanal.c (tablejump_p): Expect table and label to be adjacent.
 
 2013-05-30  Vladimir Makarov  <vmakarov@redhat.com>
 

gcc/testsuite/ChangeLog

+2013-05-30  Tobias Burnus  <burnus@net-b.de>
+
+	PR middle-end/57073
+	* gfortran.dg/power_6.f90: New.
+
 2013-05-30  Ian Bolton  <ian.bolton@arm.com>
 
 	* gcc.target/aarch64/insv_1.c: New test.

gcc/testsuite/gfortran.dg/power_6.f90

+! { dg-do compile }
+! { dg-options "-O1 -fdump-tree-optimized" }
+!
+! PR middle-end/57073
+! See also PR 57073
+!
+real function f(k)
+  integer, value :: k
+  f = (-1.0)**k
+end
+
+! { dg-final { scan-tree-dump-not "__builtin_powif"  "optimized" } }
+! { dg-final { scan-tree-dump "powi_cond_\[0-9\] = k_\[0-9\]\\(D\\) & 1;"  "optimized" } }
+! { dg-final { scan-tree-dump "powi_\[0-9\] = powi_cond_\[0-9\] \\? -1.0e\\+0 : 1.0e\\+0;"  "optimized" } }
+! { dg-final { cleanup-tree-dump "optimized" } }

gcc/tree-ssa-math-opts.c

@@ -1445,12 +1445,43 @@ execute_cse_sincos (void)
 		CASE_FLT_FN (BUILT_IN_POWI):
 		  arg0 = gimple_call_arg (stmt, 0);
 		  arg1 = gimple_call_arg (stmt, 1);
-		  if (!host_integerp (arg1, 0))
-		    break;
-
-		  n = TREE_INT_CST_LOW (arg1);
 		  loc = gimple_location (stmt);
-		  result = gimple_expand_builtin_powi (&gsi, loc, arg0, n);
+
+		  if (real_minus_onep (arg0)
+		      && TREE_CODE (TREE_TYPE (arg1)) == INTEGER_TYPE
+		      && !host_integerp (arg1,0))
+		    {
+                      tree t0, t1, cond, one, minus_one;
+		      gimple stmt;
+
+		      t0 = TREE_TYPE (arg0);
+		      t1 = TREE_TYPE (arg1);
+		      one = build_real (t0, dconst1);
+		      minus_one = build_real (t0, dconstm1);
+
+		      cond = make_temp_ssa_name (t1, NULL, "powi_cond");
+		      stmt = gimple_build_assign_with_ops (BIT_AND_EXPR, cond,
+							   arg1,
+							   build_int_cst (t1,
+									  1));
+		      gimple_set_location (stmt, loc);
+		      gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
+
+		      result = make_temp_ssa_name (t0, NULL, "powi");
+		      stmt = gimple_build_assign_with_ops (COND_EXPR, result,
+							   cond,
+							   minus_one, one);
+		      gimple_set_location (stmt, loc);
+		      gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
+		    }
+		  else
+		    {
+		      if (!host_integerp (arg1, 0))
+			break;
+
+		      n = TREE_INT_CST_LOW (arg1);
+		      result = gimple_expand_builtin_powi (&gsi, loc, arg0, n);
+		    }
 
 		  if (result)
 		    {