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.
Signed-off-by: NJoseph Myers <joseph@codesourcery.com>
Message-Id: <alpine.DEB.2.21.2005042338470.22972@digraph.polyomino.org.uk>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

fpu/softfloat.c

@@ -7966,6 +7966,13 @@ 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 {

tests/tcg/i386/test-i386-pseudo-denormal.c

@@ -20,5 +20,9 @@ int main(void)
         printf("FAIL: pseudo-denormal add\n");
         ret = 1;
     }
+    if (ld_pseudo_m16382.ld != 0x1p-16382L) {
+        printf("FAIL: pseudo-denormal compare\n");
+        ret = 1;
+    }
     return ret;
 }