softfloat: add int128_to_float128

Based on parts_sint_to_float, implements int128_to_float128 to convert a
signed 128-bit value received through an Int128 argument.

Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Message-Id: <20220330175932.6995-5-matheus.ferst@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

2 files changed, 30 insertions, 0 deletions

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 57445b36e7..60b4702945 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -3780,6 +3780,35 @@ bfloat16 int16_to_bfloat16(int16_t a, float_status *status)
     return int64_to_bfloat16_scalbn(a, 0, status);
 }
 
+float128 int128_to_float128(Int128 a, float_status *status)
+{
+    FloatParts128 p = { };
+    int shift;
+
+    if (int128_nz(a)) {
+        p.cls = float_class_normal;
+        if (!int128_nonneg(a)) {
+            p.sign = true;
+            a = int128_neg(a);
+        }
+
+        shift = clz64(int128_gethi(a));
+        if (shift == 64) {
+            shift += clz64(int128_getlo(a));
+        }
+
+        p.exp = 127 - shift;
+        a = int128_lshift(a, shift);
+
+        p.frac_hi = int128_gethi(a);
+        p.frac_lo = int128_getlo(a);
+    } else {
+        p.cls = float_class_zero;
+    }
+
+    return float128_round_pack_canonical(&p, status);
+}
+
 float128 int64_to_float128(int64_t a, float_status *status)
 {
     FloatParts128 p;
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index 8e026e5610..3994b7235d 100644
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -183,6 +183,7 @@ floatx80 int64_to_floatx80(int64_t, float_status *status);
 
 float128 int32_to_float128(int32_t, float_status *status);
 float128 int64_to_float128(int64_t, float_status *status);
+float128 int128_to_float128(Int128, float_status *status);
 float128 uint64_to_float128(uint64_t, float_status *status);
 float128 uint128_to_float128(Int128, float_status *status);