[Builtins] Implement half-precision conversions.

Mostly uninteresting, except:
- in __extendXfYf2, when checking if the number is normal, the old
  code relied on the unsignedness of src_rep_t, which is a problem
  when sizeof(src_rep_t) < sizeof(int): the result gets promoted to
  int, the signedness of which breaks the comparison.
  I added an explicit cast; it shouldn't affect other types.
- we can't pass __fp16, so src_t and src_rep_t are the same.
- the gnu_*_ieee symbols are simply duplicated definitions, as aliases
  are problematic on mach-o (where only weak aliases are supported;
  that's not what we want).

Differential Revision: http://reviews.llvm.org/D9693


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@237161 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/builtins/truncsfhf2.c b/lib/builtins/truncsfhf2.c
new file mode 100644
index 000000000..a25dd83d8
--- /dev/null
+++ b/lib/builtins/truncsfhf2.c
@@ -0,0 +1,20 @@
+//===-- lib/truncsfhf2.c - single -> half conversion --------------*- C -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#define SRC_SINGLE
+#define DST_HALF
+#include "fp_trunc_impl.inc"
+
+COMPILER_RT_ABI uint16_t __truncsfhf2(float a) {
+    return __truncXfYf2__(a);
+}
+
+COMPILER_RT_ABI uint16_t __gnu_f2h_ieee(float a) {
+    return __truncXfYf2__(a);
+}