From 0d48b436327955c69e2eb53f88aba9aa1e0dbaa0 Mon Sep 17 00:00:00 2001
From: Joseph Myers <joseph@codesourcery.com>
Date: Thu, 7 May 2020 00:44:14 +0000
Subject: 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.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>
Message-Id: <alpine.DEB.2.21.2005070043330.18350@digraph.polyomino.org.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 tests/tcg/i386/test-i386-fscale.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 tests/tcg/i386/test-i386-fscale.c

(limited to 'tests/tcg')

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;
+}
-- 
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