Re: [PATCH 04/10] fpu: Make targets specify whether floatx80 Inf can have Int bit clear

[Philippe Mathieu-Daudé]

On 17/2/25 13:50, Peter Maydell wrote:
In Intel terminology, a floatx80 Infinity with the explicit integer
bit clear is a "pseudo-infinity"; for x86 these are not valid
infinity values.  m68k is looser and does not care whether the
Integer bit is set or clear in an infinity.
Move this setting to runtime rather than using an ifdef in
floatx80_is_infinity().  (This requires us to pass in the
float_status to that function now.)

Since this was the last use of the floatx80_infinity global constant,
we remove it and its definition here.

Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>

---
  include/fpu/softfloat-types.h  |  5 +++++
  include/fpu/softfloat.h        | 20 ++++++++++++--------
  target/i386/tcg/fpu_helper.c   | 20 +++++++++++---------
  target/m68k/cpu.c              |  4 +++-
  target/m68k/fpu_helper.c       |  2 +-
  fpu/softfloat-specialize.c.inc | 10 ----------
  6 files changed, 32 insertions(+), 29 deletions(-)

Passing float_status argument to floatx80_is_infinity in a preliminary
patch, this becomes simpler (to my taste...):

   4 files changed, 19 insertions(+), 18 deletions(-)

-- >8 --
diff --git a/include/fpu/softfloat-types.h b/include/fpu/softfloat-types.h
index dd22ecdbe60..e1732beba4f 100644
--- a/include/fpu/softfloat-types.h
+++ b/include/fpu/softfloat-types.h
@@ -332,0 +333,5 @@ typedef enum __attribute__((__packed__)) {
+    /*
+     * Are Pseudo-infinities (Inf with the Integer bit zero) valid?
+     * If so, floatx80_is_infinity() will return true for them.
+     */
+    floatx80_pseudo_inf_valid = 2,
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index 1fa759779ea..1c8f3cbb78d 100644
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -963 +962,0 @@ float128 floatx80_to_float128(floatx80, float_status 
*status);
-extern const floatx80 floatx80_infinity;
@@ -1001,6 +1000,11 @@ static inline bool floatx80_is_infinity(floatx80 
a, float_status *status)
-#if defined(TARGET_M68K)
-    return (a.high & 0x7fff) == floatx80_infinity.high && !(a.low << 1);
-#else
-    return (a.high & 0x7fff) == floatx80_infinity.high &&
-                       a.low == floatx80_infinity.low;
-#endif
+    /*
+     * It's target-specific whether the Integer bit is permitted
+     * to be 0 in a valid Infinity value. (x86 says no, m68k says yes).
+     */
+    bool intbit = a.low >> 63;
+
+    if (!intbit &&
+        !(status->floatx80_behaviour & floatx80_pseudo_inf_valid)) {
+        return false;
+    }
+    return (a.high & 0x7fff) == 0x7fff && !(a.low << 1);
diff --git a/target/m68k/cpu.c b/target/m68k/cpu.c
index df66e8ba22a..56b23de21fe 100644
--- a/target/m68k/cpu.c
+++ b/target/m68k/cpu.c
@@ -112,0 +113 @@ static void m68k_cpu_reset_hold(Object *obj, ResetType 
type)
+     *  * input Infinities may have the Integer bit either 0 or 1
@@ -114 +115,2 @@ static void m68k_cpu_reset_hold(Object *obj, ResetType 
type)
-    set_floatx80_behaviour(floatx80_default_inf_int_bit_is_zero,
+    set_floatx80_behaviour(floatx80_default_inf_int_bit_is_zero |
+                           floatx80_pseudo_inf_valid,
diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index 73789e97d77..8327f727861 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -240,10 +239,0 @@ floatx80 floatx80_default_inf(bool zSign, 
float_status *status)
-#define floatx80_infinity_high 0x7FFF
-#if defined(TARGET_M68K)
-#define floatx80_infinity_low  UINT64_C(0x0000000000000000)
-#else
-#define floatx80_infinity_low  UINT64_C(0x8000000000000000)
-#endif
-
-const floatx80 floatx80_infinity
-    = make_floatx80_init(floatx80_infinity_high, floatx80_infinity_low);
-
---