[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, 13 insertions, 1 deletions

diff --git a/lib/builtins/fp_trunc.h b/lib/builtins/fp_trunc.h
index 49a9aebbc..373ba1b04 100644
--- a/lib/builtins/fp_trunc.h
+++ b/lib/builtins/fp_trunc.h
@@ -16,7 +16,13 @@
 
 #include "int_lib.h"
 
-#if defined SRC_DOUBLE
+#if defined SRC_SINGLE
+typedef float src_t;
+typedef uint32_t src_rep_t;
+#define SRC_REP_C UINT32_C
+static const int srcSigBits = 23;
+
+#elif defined SRC_DOUBLE
 typedef double src_t;
 typedef uint64_t src_rep_t;
 #define SRC_REP_C UINT64_C
@@ -44,6 +50,12 @@ typedef uint32_t dst_rep_t;
 #define DST_REP_C UINT32_C
 static const int dstSigBits = 23;
 
+#elif defined DST_HALF
+typedef uint16_t dst_t;
+typedef uint16_t dst_rep_t;
+#define DST_REP_C UINT16_C
+static const int dstSigBits = 10;
+
 #else
 #error Destination should be single precision or double precision!
 #endif //end destination precision