From: Chih-Min Chao <chihmin.chao@sifive.com>
To: qemu-devel@nongnu.org, qemu-riscv@nongnu.org
Cc: "Chih-Min Chao" <chihmin.chao@sifive.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Aurelien Jarno" <aurelien@aurel32.net>,
"Peter Maydell" <peter.maydell@linaro.org>
Subject: [PATCH 2/3] softfloat: add APIs to handle alternative sNaN propagation
Date: Thu, 30 Jul 2020 02:52:23 -0700 [thread overview]
Message-ID: <1596102747-20226-3-git-send-email-chihmin.chao@sifive.com> (raw)
In-Reply-To: <1596102747-20226-1-git-send-email-chihmin.chao@sifive.com>
For "fmax/fmin ft0, ft1, ft2" and if one of the inputs is sNaN,
The original logic
return NaN and set invalid flag if ft1 == sNaN || ft2 == sNan
The alternative path
set invalid flag if ft1 == sNaN || ft2 == sNaN
return NaN if ft1 == sNaN && ft2 == sNaN
The ieee754 spec allows both implementation and some architecture such
as riscv choose differenct defintion in two spec versions.
(riscv-spec-v2.2 use original version, riscv-spec-20191213 changes to
alternative)
Signed-off-by: Chih-Min Chao <chihmin.chao@sifive.com>
---
fpu/softfloat.c | 75 +++++++++++++++++++++++++++++++------------------
include/fpu/softfloat.h | 6 ++++
2 files changed, 54 insertions(+), 27 deletions(-)
diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 79be4f5..4466ece 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -870,11 +870,16 @@ static FloatParts return_nan(FloatParts a, float_status *s)
return a;
}
-static FloatParts pick_nan(FloatParts a, FloatParts b, float_status *s)
+static void set_snan_flag(FloatParts a, FloatParts b, float_status *s)
{
if (is_snan(a.cls) || is_snan(b.cls)) {
s->float_exception_flags |= float_flag_invalid;
}
+}
+
+static FloatParts pick_nan(FloatParts a, FloatParts b, float_status *s)
+{
+ set_snan_flag(a, b, s);
if (s->default_nan_mode) {
return parts_default_nan(s);
@@ -2743,23 +2748,32 @@ float64 uint16_to_float64(uint16_t a, float_status *status)
* and minNumMag() from the IEEE-754 2008.
*/
static FloatParts minmax_floats(FloatParts a, FloatParts b, bool ismin,
- bool ieee, bool ismag, float_status *s)
+ bool ieee, bool ismag, bool issnan_prop,
+ float_status *s)
{
if (unlikely(is_nan(a.cls) || is_nan(b.cls))) {
if (ieee) {
/* Takes two floating-point values `a' and `b', one of
* which is a NaN, and returns the appropriate NaN
* result. If either `a' or `b' is a signaling NaN,
- * the invalid exception is raised.
+ * the invalid exception is raised but the NaN
+ * propagation is 'shall'.
*/
if (is_snan(a.cls) || is_snan(b.cls)) {
- return pick_nan(a, b, s);
- } else if (is_nan(a.cls) && !is_nan(b.cls)) {
+ if (issnan_prop) {
+ return pick_nan(a, b, s);
+ } else {
+ set_snan_flag(a, b, s);
+ }
+ }
+
+ if (is_nan(a.cls) && !is_nan(b.cls)) {
return b;
} else if (is_nan(b.cls) && !is_nan(a.cls)) {
return a;
}
}
+
return pick_nan(a, b, s);
} else {
int a_exp, b_exp;
@@ -2813,37 +2827,44 @@ static FloatParts minmax_floats(FloatParts a, FloatParts b, bool ismin,
}
}
-#define MINMAX(sz, name, ismin, isiee, ismag) \
+#define MINMAX(sz, name, ismin, isiee, ismag, issnan_prop) \
float ## sz float ## sz ## _ ## name(float ## sz a, float ## sz b, \
float_status *s) \
{ \
FloatParts pa = float ## sz ## _unpack_canonical(a, s); \
FloatParts pb = float ## sz ## _unpack_canonical(b, s); \
- FloatParts pr = minmax_floats(pa, pb, ismin, isiee, ismag, s); \
+ FloatParts pr = minmax_floats(pa, pb, ismin, isiee, ismag, \
+ issnan_prop, s); \
\
return float ## sz ## _round_pack_canonical(pr, s); \
}
-MINMAX(16, min, true, false, false)
-MINMAX(16, minnum, true, true, false)
-MINMAX(16, minnummag, true, true, true)
-MINMAX(16, max, false, false, false)
-MINMAX(16, maxnum, false, true, false)
-MINMAX(16, maxnummag, false, true, true)
-
-MINMAX(32, min, true, false, false)
-MINMAX(32, minnum, true, true, false)
-MINMAX(32, minnummag, true, true, true)
-MINMAX(32, max, false, false, false)
-MINMAX(32, maxnum, false, true, false)
-MINMAX(32, maxnummag, false, true, true)
-
-MINMAX(64, min, true, false, false)
-MINMAX(64, minnum, true, true, false)
-MINMAX(64, minnummag, true, true, true)
-MINMAX(64, max, false, false, false)
-MINMAX(64, maxnum, false, true, false)
-MINMAX(64, maxnummag, false, true, true)
+MINMAX(16, min, true, false, false, true)
+MINMAX(16, minnum, true, true, false, true)
+MINMAX(16, minnum_noprop, true, true, false, false)
+MINMAX(16, minnummag, true, true, true, true)
+MINMAX(16, max, false, false, false, true)
+MINMAX(16, maxnum, false, true, false, true)
+MINMAX(16, maxnum_noprop, false, true, false, false)
+MINMAX(16, maxnummag, false, true, true, true)
+
+MINMAX(32, min, true, false, false, true)
+MINMAX(32, minnum, true, true, false, true)
+MINMAX(32, minnum_noprop, true, true, false, false)
+MINMAX(32, minnummag, true, true, true, true)
+MINMAX(32, max, false, false, false, true)
+MINMAX(32, maxnum, false, true, false, true)
+MINMAX(32, maxnum_noprop, false, true, false, false)
+MINMAX(32, maxnummag, false, true, true, true)
+
+MINMAX(64, min, true, false, false, true)
+MINMAX(64, minnum, true, true, false, true)
+MINMAX(64, minnum_noprop, true, true, false, false)
+MINMAX(64, minnummag, true, true, true, true)
+MINMAX(64, max, false, false, false, true)
+MINMAX(64, maxnum, false, true, false, true)
+MINMAX(64, maxnum_noprop, false, true, false, false)
+MINMAX(64, maxnummag, false, true, true, true)
#undef MINMAX
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index 573fce9..65842b0 100644
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -231,6 +231,8 @@ float16 float16_minnum(float16, float16, float_status *status);
float16 float16_maxnum(float16, float16, float_status *status);
float16 float16_minnummag(float16, float16, float_status *status);
float16 float16_maxnummag(float16, float16, float_status *status);
+float16 float16_minnum_noprop(float16, float16, float_status *status);
+float16 float16_maxnum_noprop(float16, float16, float_status *status);
float16 float16_sqrt(float16, float_status *status);
FloatRelation float16_compare(float16, float16, float_status *status);
FloatRelation float16_compare_quiet(float16, float16, float_status *status);
@@ -392,6 +394,8 @@ float32 float32_minnum(float32, float32, float_status *status);
float32 float32_maxnum(float32, float32, float_status *status);
float32 float32_minnummag(float32, float32, float_status *status);
float32 float32_maxnummag(float32, float32, float_status *status);
+float32 float32_minnum_noprop(float32, float32, float_status *status);
+float32 float32_maxnum_noprop(float32, float32, float_status *status);
bool float32_is_quiet_nan(float32, float_status *status);
bool float32_is_signaling_nan(float32, float_status *status);
float32 float32_silence_nan(float32, float_status *status);
@@ -581,6 +585,8 @@ float64 float64_minnum(float64, float64, float_status *status);
float64 float64_maxnum(float64, float64, float_status *status);
float64 float64_minnummag(float64, float64, float_status *status);
float64 float64_maxnummag(float64, float64, float_status *status);
+float64 float64_minnum_noprop(float64, float64, float_status *status);
+float64 float64_maxnum_noprop(float64, float64, float_status *status);
bool float64_is_quiet_nan(float64 a, float_status *status);
bool float64_is_signaling_nan(float64, float_status *status);
float64 float64_silence_nan(float64, float_status *status);
--
2.7.4
next prev parent reply other threads:[~2020-07-30 9:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-30 9:52 [PATCH 0/3] float16 APIs and alternative sNaN handling Chih-Min Chao
2020-07-30 9:52 ` [PATCH 1/3] softfloat: target/riscv: implement full set fp16 comparision Chih-Min Chao
2020-08-12 16:30 ` Alistair Francis
2020-08-13 17:22 ` Richard Henderson
2020-07-30 9:52 ` Chih-Min Chao [this message]
2020-08-13 17:21 ` [PATCH 2/3] softfloat: add APIs to handle alternative sNaN propagation Richard Henderson
2020-08-14 8:59 ` Chih-Min Chao
2020-08-14 16:15 ` Richard Henderson
2020-07-30 9:52 ` [PATCH 3/3] softfloat: add fp16 and uint8/int8 interconvert functions Chih-Min Chao
2020-08-13 17:25 ` Richard Henderson
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