AVR: target/114981 - Support __builtin_powi[l] / __powidf2.

This supports __powidf2 by means of a double wrapper for already
existing f7_powi (renamed to __f7_powi by f7-renames.h).
It tweaks the implementation so that it does not perform trivial
multiplications with 1.0 any more, but instead uses a move.
It also fixes the last statement of f7_powi, which was wrong.
Notice that f7_powi was unused until now.

	PR target/114981
libgcc/config/avr/libf7/
	* libf7-common.mk (F7_ASM_PARTS): Add D_powi
	* libf7-asm.sx (F7MOD_D_powi_, __powidf2): New module and function.
	* libf7.c (f7_powi): Fix last (wrong) statement.
	Tweak trivial multiplications with 1.0.

gcc/testsuite/
	* gcc.target/avr/pr114981-powil.c: New test.

1 files changed, 33 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.target/avr/pr114981-powil.c b/gcc/testsuite/gcc.target/avr/pr114981-powil.c
new file mode 100644
index 0000000..70f8e79
--- /dev/null
+++ b/gcc/testsuite/gcc.target/avr/pr114981-powil.c
@@ -0,0 +1,33 @@
+/* { dg-do run { target { ! avr_tiny } } } */
+/* { dg-additional-options "-Os" } */
+
+const long double vals[] =
+  {
+    0.0625L, -0.125L, 0.25L, -0.5L,
+    1.0L,
+    -2.0L, 4.0L, -8.0L, 16.0L
+  };
+
+#define ARRAY_SIZE(X) ((int) (sizeof(X) / sizeof(*X)))
+
+__attribute__((noinline,noclone))
+void test1 (long double x)
+{
+  int i;
+
+  for (i = 0; i < ARRAY_SIZE (vals); ++i)
+    {
+      long double val0 = vals[i];
+      long double val1 = __builtin_powil (x, i - 4);
+      __asm ("" : "+r" (val0));
+
+      if (val0 != val1)
+	__builtin_exit (__LINE__);
+    }
+}
+
+int main (void)
+{
+  test1 (-2.0L);
+  return 0;
+}