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[PATCH 2/5] target/i386: fix fscale handling of signaling NaN
From: |
Joseph Myers |
Subject: |
[PATCH 2/5] target/i386: fix fscale handling of signaling NaN |
Date: |
Thu, 7 May 2020 00:44:14 +0000 |
User-agent: |
Alpine 2.21 (DEB 202 2017-01-01) |
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.
Signed-off-by: Joseph Myers <address@hidden>
---
target/i386/fpu_helper.c | 4 ++++
tests/tcg/i386/test-i386-fscale.c | 37 +++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+)
create mode 100644 tests/tcg/i386/test-i386-fscale.c
diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c
index 71a696a863..60012c405c 100644
--- a/target/i386/fpu_helper.c
+++ b/target/i386/fpu_helper.c
@@ -970,6 +970,10 @@ 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);
diff --git a/tests/tcg/i386/test-i386-fscale.c
b/tests/tcg/i386/test-i386-fscale.c
new file mode 100644
index 0000000000..aecac5125f
--- /dev/null
+++ b/tests/tcg/i386/test-i386-fscale.c
@@ -0,0 +1,37 @@
+/* Test fscale instruction. */
+
+#include <stdint.h>
+#include <stdio.h>
+
+union u {
+ struct { uint64_t sig; uint16_t sign_exp; } s;
+ long double ld;
+};
+
+volatile long double ld_res;
+
+int isnan_ld(long double x)
+{
+ union u tmp = { .ld = x };
+ return ((tmp.s.sign_exp & 0x7fff) == 0x7fff &&
+ (tmp.s.sig >> 63) != 0 &&
+ (tmp.s.sig << 1) != 0);
+}
+
+int issignaling_ld(long double x)
+{
+ union u tmp = { .ld = x };
+ return isnan_ld(x) && (tmp.s.sig & UINT64_C(0x4000000000000000)) == 0;
+}
+
+int main(void)
+{
+ int ret = 0;
+ __asm__ volatile ("fscale" : "=t" (ld_res) :
+ "0" (2.5L), "u" (__builtin_nansl("")));
+ if (!isnan_ld(ld_res) || issignaling_ld(ld_res)) {
+ printf("FAIL: fscale snan\n");
+ ret = 1;
+ }
+ return ret;
+}
--
2.17.1
--
Joseph S. Myers
address@hidden
- [PATCH 0/5] target/i386: fxtract, fscale fixes, Joseph Myers, 2020/05/06
- [PATCH 1/5] target/i386: implement special cases for fxtract, Joseph Myers, 2020/05/06
- [PATCH 2/5] target/i386: fix fscale handling of signaling NaN,
Joseph Myers <=
- [PATCH 3/5] target/i386: fix fscale handling of invalid exponent encodings, Joseph Myers, 2020/05/06
- [PATCH 4/5] target/i386: fix fscale handling of infinite exponents, Joseph Myers, 2020/05/06
- [PATCH 5/5] target/i386: fix fscale handling of rounding precision, Joseph Myers, 2020/05/06
- Re: [PATCH 0/5] target/i386: fxtract, fscale fixes, no-reply, 2020/05/06
- Ping Re: [PATCH 0/5] target/i386: fxtract, fscale fixes, Joseph Myers, 2020/05/14
- Re: [PATCH 0/5] target/i386: fxtract, fscale fixes, Philippe Mathieu-Daudé, 2020/05/15
- Re: [PATCH 0/5] target/i386: fxtract, fscale fixes, Paolo Bonzini, 2020/05/21