The ldbl-128ibm implementations of lrintl and lroundl are missing
"invalid" exceptions for certain overflow cases when compiled with GCC
8. The cause of this is after-the-fact integer overflow checks that
fail when the compiler optimizes on the basis of integer overflow
being undefined; GCC 8 must be able to detect new cases of
undefinedness here.
Failure: lrint (-0x80000001p0): Exception "Invalid operation" not set
Failure: lrint_downward (-0x80000001p0): Exception "Invalid operation" not set
Failure: lrint_towardzero (-0x80000001p0): Exception "Invalid operation" not set
Failure: lrint_upward (-0x80000001p0): Exception "Invalid operation" not set
Failure: lround (-0x80000001p0): Exception "Invalid operation" not set
Failure: lround_downward (-0x80000001p0): Exception "Invalid operation" not set
Failure: lround_towardzero (-0x80000001p0): Exception "Invalid operation" not set
Failure: lround_upward (-0x80000001p0): Exception "Invalid operation" not set
(Tested that these failures occur before the patch for powerpc
soft-float, but the issue applies in principle for hard-float as well,
whether or not the particular optimizations in fact occur there at
present.)
This patch fixes the bug by ensuring the additions / subtractions in
question cast arguments to unsigned long int, or use 1UL as a constant
argument, so that the arithmetic occurs in an unsigned type with the
result then converted back to a signed type.
Tested for powerpc (soft-float).
[BZ #22690]
* sysdeps/ieee754/ldbl-128ibm/s_lrintl.c (__lrintl): Use unsigned
long int for arguments of possibly overflowing addition or
subtraction.
* sysdeps/ieee754/ldbl-128ibm/s_lroundl.c (__lroundl): Likewise.
+2018-01-10 Joseph Myers <joseph@codesourcery.com>
+
+ [BZ #22690]
+ * sysdeps/ieee754/ldbl-128ibm/s_lrintl.c (__lrintl): Use unsigned
+ long int for arguments of possibly overflowing addition or
+ subtraction.
+ * sysdeps/ieee754/ldbl-128ibm/s_lroundl.c (__lroundl): Likewise.
+
2018-01-09 Joseph Myers <joseph@codesourcery.com>
[BZ #22688]
/* Peg at max/min values, assuming that the above conversions do so.
Strictly speaking, we can return anything for values that overflow,
but this is more useful. */
- res = hi + lo;
+ res = (long int) ((unsigned long int) hi + (unsigned long int) lo);
/* This is just sign(hi) == sign(lo) && sign(res) != sign(hi). */
if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
return res;
if (xh < 0.0)
- res -= 1;
+ res -= 1UL;
else
- res += 1;
+ res += 1UL;
break;
case FE_TOWARDZERO:
if (res > 0 && (xh < 0.0 || (xh == 0.0 && xl < 0.0)))
- res -= 1;
+ res -= 1UL;
else if (res < 0 && (xh > 0.0 || (xh == 0.0 && xl > 0.0)))
- res += 1;
+ res += 1UL;
return res;
break;
case FE_UPWARD:
if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
- res += 1;
+ res += 1UL;
break;
case FE_DOWNWARD:
if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
- res -= 1;
+ res -= 1UL;
break;
}
/* Peg at max/min values, assuming that the above conversions do so.
Strictly speaking, we can return anything for values that overflow,
but this is more useful. */
- res = hi + lo;
+ res = (long int) ((unsigned long int) hi + (unsigned long int) lo);
/* This is just sign(hi) == sign(lo) && sign(res) != sign(hi). */
if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
hi = res;
if (xh > 0.5)
{
- res += 1;
+ res += 1UL;
}
else if (xh == 0.5)
{
if (xl > 0.0 || (xl == 0.0 && res >= 0))
- res += 1;
+ res += 1UL;
}
else if (-xh > 0.5)
{
- res -= 1;
+ res -= 1UL;
}
else if (-xh == 0.5)
{
if (xl < 0.0 || (xl == 0.0 && res <= 0))
- res -= 1;
+ res -= 1UL;
}
if (__glibc_unlikely (((~(hi ^ (res - hi)) & (res ^ hi)) < 0)))