[PATCH v2 3/4] softfloat: fix floatx80 pseudo-denormal comparisons

[Joseph Myers]

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.

Note that this fix only changes floatx80_compare_internal, not the
other more specific comparison operations.  That is the only
comparison function for floatx80 used in the i386 port, which is the
only supported port with these pseudo-denormal semantics.

Signed-off-by: Joseph Myers <jos...@codesourcery.com>
---
 fpu/softfloat.c                            | 5 +++++
 tests/tcg/i386/test-i386-pseudo-denormal.c | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 6094d267b5..8e9c714e6f 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -7966,6 +7966,11 @@ 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 {
diff --git a/tests/tcg/i386/test-i386-pseudo-denormal.c 
b/tests/tcg/i386/test-i386-pseudo-denormal.c
index cfa2a500b0..acf2b9cf03 100644
--- a/tests/tcg/i386/test-i386-pseudo-denormal.c
+++ b/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;
 }
-- 
2.17.1


-- 
Joseph S. Myers
jos...@codesourcery.com