[PULL,3/4] softfloat: fix floatx80 pseudo-denormal comparisons

Message ID 20200515184722.31182-4-richard.henderson@linaro.org
State New
Headers show
Series
  • softfloat patch queue
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Commit Message

Richard Henderson May 15, 2020, 6:47 p.m.
From: Joseph Myers <joseph@codesourcery.com>


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: Joseph Myers <joseph@codesourcery.com>

Message-Id: <alpine.DEB.2.21.2005042338470.22972@digraph.polyomino.org.uk>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

---
 fpu/softfloat.c                            | 7 +++++++
 tests/tcg/i386/test-i386-pseudo-denormal.c | 4 ++++
 2 files changed, 11 insertions(+)

-- 
2.20.1

Patch

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 6094d267b5..c57f72e3a6 100644
--- a/fpu/softfloat.c
+++ b/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 {
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;
 }