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[PULL,16/31] softfloat: fix floatx80 remainder pseudo-denormal check for zero

Message ID 20200624105048.375353-16-pbonzini@redhat.com
State New
Headers show
Series Misc patches for 2020-06-24 | expand

Commit Message

Paolo Bonzini June 24, 2020, 10:50 a.m. UTC 
From: Joseph Myers <joseph@codesourcery.com>

The floatx80 remainder implementation ignores the high bit of the
significand when checking whether an operand (numerator) with zero
exponent is zero.  This means it mishandles a pseudo-denormal
representation of 0x1p-16382L by treating it as zero.  Fix this by
checking the whole significand instead.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <alpine.DEB.2.21.2006081655180.23637@digraph.polyomino.org.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 fpu/softfloat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index b7dcf4d6c3..f164b5c0ad 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -5741,7 +5741,7 @@  floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
         normalizeFloatx80Subnormal( bSig, &bExp, &bSig );
     }
     if ( aExp == 0 ) {
-        if ( (uint64_t) ( aSig0<<1 ) == 0 ) return a;
+        if ( aSig0 == 0 ) return a;
         normalizeFloatx80Subnormal( aSig0, &aExp, &aSig0 );
     }
     bSig |= UINT64_C(0x8000000000000000);