On 17/2/25 13:50, Peter Maydell wrote:
(1) floatx80 behaviours
Two QEMU targets implement floatx80: x86 and m68k. (PPC also has one
use in the xsrqpxp round-to-80-bit-precision operation, and the
Linux-user NWFPE emulation nominally supports it, but these are
minor.) x86 and m68k disagree about some of the corner cases of
floatx80 where the value has the explicit Integer bit wrongly set. At
the moment the fpu code defaults to "floatx80 behaves like x86", with
TARGET_M68K ifdefs to get the other option.
The first six patches in this series remove those ifdefs, replacing
them with a floatx80_behaviour field in float_status which can have
various flags set to select the individual behaviours. The default is
"like x86", which allows us to set these only for m68k and not worry
about the minor "technically makes some use of floatx80" cases.
Peter Maydell (10):
fpu: Make targets specify floatx80 default Inf at runtime
target/m68k: Avoid using floatx80_infinity global const
target/i386: Avoid using floatx80_infinity global const
Bothering again, we can add the floatx80_default_inf() refactor as the
first patch:
-- >8 --
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index 09a40b43106..afae3906024 100644
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -963,0 +964 @@ extern const floatx80 floatx80_infinity;
+floatx80 floatx80_default_inf(bool zSign, float_status *status);
diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index f4fed9bfda9..f56ae886c53 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -5147,3 +5147 @@ floatx80 roundAndPackFloatx80(FloatX80RoundPrec
roundingPrecision, bool zSign,
- return packFloatx80(zSign,
- floatx80_infinity_high,
- floatx80_infinity_low);
+ return floatx80_default_inf(zSign, status);
diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
index f112c6c6737..741af09f908 100644
--- a/target/i386/tcg/fpu_helper.c
+++ b/target/i386/tcg/fpu_helper.c
@@ -1835 +1835 @@ void helper_fxtract(CPUX86State *env)
- ST1 = floatx80_infinity;
+ ST1 = floatx80_default_inf(0, &env->fp_status);
@@ -2361,3 +2361,2 @@ void helper_fscale(CPUX86State *env)
- ST0 = (floatx80_is_neg(ST0) ?
- floatx80_chs(floatx80_infinity) :
- floatx80_infinity);
+ ST0 = floatx80_default_inf(floatx80_is_neg(ST0),
+ &env->fp_status);
diff --git a/target/m68k/softfloat.c b/target/m68k/softfloat.c
index 02dcc03d15d..d1f150e641f 100644
--- a/target/m68k/softfloat.c
+++ b/target/m68k/softfloat.c
@@ -145,2 +145 @@ floatx80 floatx80_scale(floatx80 a, floatx80 b,
float_status *status)
- return packFloatx80(aSign, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(aSign, status);
@@ -248 +247 @@ floatx80 floatx80_lognp1(floatx80 a, float_status *status)
- return packFloatx80(0, floatx80_infinity.high,
floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
@@ -258,2 +257 @@ floatx80 floatx80_lognp1(floatx80 a, float_status *status)
- return packFloatx80(aSign, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(aSign, status);
@@ -445,2 +443 @@ floatx80 floatx80_logn(floatx80 a, float_status *status)
- return packFloatx80(0, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
@@ -455,2 +452 @@ floatx80 floatx80_logn(floatx80 a, float_status *status)
- return packFloatx80(1, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(1, status);
@@ -613,2 +609 @@ floatx80 floatx80_log10(floatx80 a, float_status *status)
- return packFloatx80(0, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
@@ -620,2 +615 @@ floatx80 floatx80_log10(floatx80 a, float_status *status)
- return packFloatx80(1, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(1, status);
@@ -671,2 +665 @@ floatx80 floatx80_log2(floatx80 a, float_status *status)
- return packFloatx80(0, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
@@ -679,2 +672 @@ floatx80 floatx80_log2(floatx80 a, float_status *status)
- return packFloatx80(1, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(1, status);
@@ -743,2 +735 @@ floatx80 floatx80_etox(floatx80 a, float_status *status)
- return packFloatx80(0, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
@@ -927,2 +918 @@ floatx80 floatx80_twotox(floatx80 a, float_status *status)
- return packFloatx80(0, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
@@ -1078,2 +1068 @@ floatx80 floatx80_tentox(floatx80 a, float_status
*status)
- return packFloatx80(0, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
@@ -2263,2 +2252 @@ floatx80 floatx80_atanh(floatx80 a, float_status
*status)
- return packFloatx80(aSign, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(aSign, status);
@@ -2323,2 +2311 @@ floatx80 floatx80_etoxm1(floatx80 a, float_status
*status)
- return packFloatx80(0, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
@@ -2690,2 +2677 @@ floatx80 floatx80_sinh(floatx80 a, float_status *status)
- return packFloatx80(aSign, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(aSign, status);
@@ -2777,2 +2763 @@ floatx80 floatx80_cosh(floatx80 a, float_status *status)
- return packFloatx80(0, floatx80_infinity.high,
- floatx80_infinity.low);
+ return floatx80_default_inf(0, status);
diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index cbbbab52ba3..403f7a9d69d 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -239,0 +240,5 @@ const floatx80 floatx80_infinity
+floatx80 floatx80_default_inf(bool zSign, float_status *status)
+{
+ return packFloatx80(zSign, floatx80_infinity_high,
floatx80_infinity_low);
+}
+
---
The single non-obvious thing to mention is the x86 floatx80_chs()
removal.
This effectively absorb patch #3 (x86).
Then patch #2 (m68k) becomes:
-- >8 --
diff --git a/include/fpu/softfloat-helpers.h
b/include/fpu/softfloat-helpers.h
index 8983c2748ec..90862f5cd22 100644
--- a/include/fpu/softfloat-helpers.h
+++ b/include/fpu/softfloat-helpers.h
@@ -77,0 +78,6 @@ static inline void
set_floatx80_rounding_precision(FloatX80RoundPrec val,
+static inline void set_floatx80_behaviour(FloatX80Behaviour b,
+ float_status *status)
+{
+ status->floatx80_behaviour = b;
+}
+
@@ -153,0 +160,6 @@ get_floatx80_rounding_precision(const float_status
*status)
+static inline FloatX80Behaviour
+get_floatx80_behaviour(const float_status *status)
+{
+ return status->floatx80_behaviour;
+}
+
diff --git a/include/fpu/softfloat-types.h b/include/fpu/softfloat-types.h
index 53d5eb85210..dd22ecdbe60 100644
--- a/include/fpu/softfloat-types.h
+++ b/include/fpu/softfloat-types.h
@@ -322,0 +323,12 @@ typedef enum __attribute__((__packed__)) {
+/*
+ * floatx80 is primarily used by x86 and m68k, and there are
+ * differences in the handling, largely related to the explicit
+ * Integer bit which floatx80 has and the other float formats do not.
+ * These flag values allow specification of the target's requirements
+ * and can be ORed together to set floatx80_behaviour.
+ */
+typedef enum __attribute__((__packed__)) {
+ /* In the default Infinity value, is the Integer bit 0 ? */
+ floatx80_default_inf_int_bit_is_zero = 1,
+} FloatX80Behaviour;
+
@@ -333,0 +346 @@ typedef struct float_status {
+ FloatX80Behaviour floatx80_behaviour;
diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index f56ae886c53..b12ad2b42a9 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -1863 +1863,2 @@ static floatx80
floatx80_round_pack_canonical(FloatParts128 *p,
- frac = floatx80_infinity_low;
+ frac = s->floatx80_behaviour &
floatx80_default_inf_int_bit_is_zero ?
+ 0 : (1ULL << 63);
diff --git a/target/m68k/cpu.c b/target/m68k/cpu.c
index 41dfdf58045..df66e8ba22a 100644
--- a/target/m68k/cpu.c
+++ b/target/m68k/cpu.c
@@ -109,0 +110,6 @@ static void m68k_cpu_reset_hold(Object *obj,
ResetType type)
+ /*
+ * m68k-specific floatx80 behaviour:
+ * * default Infinity values have a zero Integer bit
+ */
+ set_floatx80_behaviour(floatx80_default_inf_int_bit_is_zero,
+ &env->fp_status);
diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index 403f7a9d69d..77a43f46597 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -242 +242,6 @@ floatx80 floatx80_default_inf(bool zSign, float_status
*status)
- return packFloatx80(zSign, floatx80_infinity_high,
floatx80_infinity_low);
+ /*
+ * Whether the Integer bit is set in the default Infinity is
+ * target dependent.
+ */
+ bool z = status->floatx80_behaviour &
floatx80_default_inf_int_bit_is_zero;
+ return packFloatx80(zSign, 0x7fff, z ? 0 : (1ULL << 63));
---
