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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: 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>
This commit is contained in:
Joseph Myers 2020-05-04 23:39:39 +00:00 committed by Richard Henderson
parent 4160280776
commit be53fa785a
2 changed files with 11 additions and 0 deletions
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7
fpu/softfloat.c
View File

@ -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 {

4
tests/tcg/i386/test-i386-pseudo-denormal.c
View File

@ -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;
}