From d96c2186641845e93ef45130e2ccf74fe9f30aa4 Mon Sep 17 00:00:00 2001
From: Joseph Myers <joseph@codesourcery.com>
Date: Mon, 15 Jun 2020 13:03:14 -0400
Subject: [PATCH] target/i386: fix fscale handling of signaling NaN
The implementation of the fscale instruction returns a NaN exponent
unchanged. Fix it to return a quiet NaN when the provided exponent is
a signaling NaN.
Backports commit 0d48b436327955c69e2eb53f88aba9aa1e0dbaa0 from qemu
---
qemu/target/i386/fpu_helper.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/qemu/target/i386/fpu_helper.c b/qemu/target/i386/fpu_helper.c
index da730b1c..d38e3479 100644
--- a/qemu/target/i386/fpu_helper.c
+++ b/qemu/target/i386/fpu_helper.c
@@ -936,6 +936,10 @@ void helper_fscale(CPUX86State *env)
{
if (floatx80_is_any_nan(ST1)) {
ST0 = ST1;
+ if (floatx80_is_signaling_nan(ST0, &env->fp_status)) {
+ float_raise(float_flag_invalid, &env->fp_status);
+ ST0 = floatx80_silence_nan(ST0, &env->fp_status);
+ }
} else {
int n = floatx80_to_int32_round_to_zero(ST1, &env->fp_status);
ST0 = floatx80_scalbn(ST0, n, &env->fp_status);