From: Max Chou <max.chou@sifive.com>

ARM Alt HP raises different exceptions on overflow than is
standard for IEEE when saturating a value.  Add a flag to
control this effect.

Signed-off-by: Max Chou <max.chou@sifive.com>
[rth: Split out of a larger patch]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 fpu/softfloat.c           | 6 +++++-
 fpu/softfloat-parts.c.inc | 4 +++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 18098c4cdd..209eb59b48 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -542,7 +542,9 @@ typedef enum __attribute__((__packed__)) {
  * The following optional modifiers are available:
  *   exp_max_kind: affects how exp == exp_max is interpreted
  *   has_explicit_bit: has an explicit integer bit; this affects whether
- *   the float_status floatx80_behaviour handling applies
+ *       the float_status floatx80_behaviour handling applies
+ *   overflow_raises_invalid: for float_expmax_normal, raise invalid
+ *       instead of overflow.
  */
 typedef struct {
     int exp_size;
@@ -553,6 +555,7 @@ typedef struct {
     int frac_shift;
     FloatFmtExpMaxKind exp_max_kind;
     bool has_explicit_bit;
+    bool overflow_raises_invalid;
     uint64_t round_mask;
 } FloatFmt;
 
@@ -576,6 +579,7 @@ static const FloatFmt float16_params = {
 static const FloatFmt float16_params_ahp = {
     FLOAT_PARAMS(5, 10),
     .exp_max_kind = float_expmax_normal,
+    .overflow_raises_invalid = true,
 };
 
 static const FloatFmt bfloat16_params = {
diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc
index d3c9c7a913..eada83f7a4 100644
--- a/fpu/softfloat-parts.c.inc
+++ b/fpu/softfloat-parts.c.inc
@@ -348,7 +348,9 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s,
             case float_expmax_normal:
                 if (unlikely(exp > exp_max)) {
                     /* Overflow.  Return the maximum normal.  */
-                    flags = float_flag_invalid;
+                    flags = (fmt->overflow_raises_invalid
+                             ? float_flag_invalid
+                             : float_flag_overflow | float_flag_inexact);
                     exp = exp_max;
                     frac_allones(p);
                     p->frac_lo &= ~round_mask;
-- 
2.43.0