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| author | Joseph Myers | 2020-05-07 02:46:28 +0200 |
|---|---|---|
| committer | Paolo Bonzini | 2020-06-10 18:10:21 +0200 |
| commit | c535d68755576bfa33be7aef7bd294a601f776e0 (patch) | |
| tree | a38e6c956706bdc5786520ade140301433ef73e2 /target/i386/fpu_helper.c | |
| parent | target/i386: fix fscale handling of infinite exponents (diff) | |
| download | qemu-c535d68755576bfa33be7aef7bd294a601f776e0.tar.gz qemu-c535d68755576bfa33be7aef7bd294a601f776e0.tar.xz qemu-c535d68755576bfa33be7aef7bd294a601f776e0.zip | |
target/i386: fix fscale handling of rounding precision
The fscale implementation uses floatx80_scalbn for the final scaling
operation. floatx80_scalbn ends up rounding the result using the
dynamic rounding precision configured for the FPU. But only a limited
set of x87 floating-point instructions are supposed to respect the
dynamic rounding precision, and fscale is not in that set. Fix the
implementation to save and restore the rounding precision around the
call to floatx80_scalbn.
Signed-off-by: Joseph Myers <joseph@codesourcery.com>
Message-Id: <alpine.DEB.2.21.2005070045430.18350@digraph.polyomino.org.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'target/i386/fpu_helper.c')
| -rw-r--r-- | target/i386/fpu_helper.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c index 72d1e77eb0..4d14c1ca24 100644 --- a/target/i386/fpu_helper.c +++ b/target/i386/fpu_helper.c @@ -1001,7 +1001,10 @@ void helper_fscale(CPUX86State *env) } } else { int n = floatx80_to_int32_round_to_zero(ST1, &env->fp_status); + signed char save = env->fp_status.floatx80_rounding_precision; + env->fp_status.floatx80_rounding_precision = 80; ST0 = floatx80_scalbn(ST0, n, &env->fp_status); + env->fp_status.floatx80_rounding_precision = save; } } |