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[Qemu-devel] [PATCH] fpu/softfloat: check for Inf / x or 0 / x before /0
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [PATCH] fpu/softfloat: check for Inf / x or 0 / x before /0 |
Date: |
Mon, 16 Apr 2018 14:54:42 +0100 |
The re-factoring of div_floats changed the order of checking meaning
an operation like -inf/0 erroneously raises the divbyzero flag.
IEEE-754 (2008) specifies this should only occur for operations on
finite operands.
We fix this by moving the check on the dividend being Inf/0 to before
the divisor is zero check.
Signed-off-by: Alex Bennée <address@hidden>
Cc: Bastian Koppelmann <address@hidden>
---
fpu/softfloat.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index b46dccc63e..a7d0f3ff56 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -1146,6 +1146,11 @@ static FloatParts div_floats(FloatParts a, FloatParts b,
float_status *s)
a.cls = float_class_dnan;
return a;
}
+ /* Inf / x or 0 / x */
+ if (a.cls == float_class_inf || a.cls == float_class_zero) {
+ a.sign = sign;
+ return a;
+ }
/* Div 0 => Inf */
if (b.cls == float_class_zero) {
s->float_exception_flags |= float_flag_divbyzero;
@@ -1153,11 +1158,6 @@ static FloatParts div_floats(FloatParts a, FloatParts b,
float_status *s)
a.sign = sign;
return a;
}
- /* Inf / x or 0 / x */
- if (a.cls == float_class_inf || a.cls == float_class_zero) {
- a.sign = sign;
- return a;
- }
/* Div by Inf */
if (b.cls == float_class_inf) {
a.cls = float_class_zero;
--
2.17.0
- [Qemu-devel] [PATCH] fpu/softfloat: check for Inf / x or 0 / x before /0,
Alex Bennée <=