target/arm: Fix float16 to/from int16

[mirror_qemu.git] / target / arm / helper.c

diff --git a/target/arm/helper.c b/target/arm/helper.c
index b14fdab14055f9855b38877e76d96d23afd9b34d..c07c1d7f48b2071e479064f2ee648a9d9050c839 100644 (file)
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -11409,11 +11409,60 @@ VFP_CONV_FIX_A64(sq, s, 32, 64, int64)
 VFP_CONV_FIX(uh, s, 32, 32, uint16)
 VFP_CONV_FIX(ul, s, 32, 32, uint32)
 VFP_CONV_FIX_A64(uq, s, 32, 64, uint64)
-VFP_CONV_FIX_A64(sl, h, 16, 32, int32)
-VFP_CONV_FIX_A64(ul, h, 16, 32, uint32)
+
 #undef VFP_CONV_FIX
 #undef VFP_CONV_FIX_FLOAT
 #undef VFP_CONV_FLOAT_FIX_ROUND
+#undef VFP_CONV_FIX_A64
+
+/* Conversion to/from f16 can overflow to infinity before/after scaling.
+ * Therefore we convert to f64 (which does not round), scale,
+ * and then convert f64 to f16 (which may round).
+ */
+
+static float16 do_postscale_fp16(float64 f, int shift, float_status *fpst)
+{
+    return float64_to_float16(float64_scalbn(f, -shift, fpst), true, fpst);
+}
+
+float16 HELPER(vfp_sltoh)(uint32_t x, uint32_t shift, void *fpst)
+{
+    return do_postscale_fp16(int32_to_float64(x, fpst), shift, fpst);
+}
+
+float16 HELPER(vfp_ultoh)(uint32_t x, uint32_t shift, void *fpst)
+{
+    return do_postscale_fp16(uint32_to_float64(x, fpst), shift, fpst);
+}
+
+static float64 do_prescale_fp16(float16 f, int shift, float_status *fpst)
+{
+    if (unlikely(float16_is_any_nan(f))) {
+        float_raise(float_flag_invalid, fpst);
+        return 0;
+    } else {
+        int old_exc_flags = get_float_exception_flags(fpst);
+        float64 ret;
+
+        ret = float16_to_float64(f, true, fpst);
+        ret = float64_scalbn(ret, shift, fpst);
+        old_exc_flags |= get_float_exception_flags(fpst)
+            & float_flag_input_denormal;
+        set_float_exception_flags(old_exc_flags, fpst);
+
+        return ret;
+    }
+}
+
+uint32_t HELPER(vfp_toshh)(float16 x, uint32_t shift, void *fpst)
+{
+    return float64_to_int16(do_prescale_fp16(x, shift, fpst), fpst);
+}
+
+uint32_t HELPER(vfp_touhh)(float16 x, uint32_t shift, void *fpst)
+{
+    return float64_to_uint16(do_prescale_fp16(x, shift, fpst), fpst);
+}
 
 /* Set the current fp rounding mode and return the old one.
  * The argument is a softfloat float_round_ value.