From 3d4a7e34e18593e77dae4947de2db25e9df65a51 Mon Sep 17 00:00:00 2001
From: Joseph Myers <joseph@codesourcery.com>
Date: Fri, 15 May 2020 23:58:47 -0400
Subject: [PATCH] softfloat: fix floatx80 pseudo-denormal comparisons

The softfloat floatx80 comparisons fail to allow for pseudo-denormals,
which should compare equal to corresponding values with biased
exponent 1 rather than 0. Add an adjustment for that case when
comparing numbers with the same sign.

Backports commit be53fa785ab766d2722628403edee75b3e6ab599 from qemu
---
 qemu/fpu/softfloat.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/qemu/fpu/softfloat.c b/qemu/fpu/softfloat.c
index 6aac46eb..199dfa47 100644
--- a/qemu/fpu/softfloat.c
+++ b/qemu/fpu/softfloat.c
@@ -7928,6 +7928,13 @@ static inline int floatx80_compare_internal(floatx80 a, floatx80 b,
             return 1 - (2 * aSign);
         }
     } else {
+        /* Normalize pseudo-denormals before comparison.  */
+        if ((a.high & 0x7fff) == 0 && a.low & UINT64_C(0x8000000000000000)) {
+            ++a.high;
+        }
+        if ((b.high & 0x7fff) == 0 && b.low & UINT64_C(0x8000000000000000)) {
+            ++b.high;
+        }
         if (a.low == b.low && a.high == b.high) {
             return float_relation_equal;
         } else {