1. Previously, printing the number 1.0 could produce 0x1p+0, 0x2p-1,
0x4p-2, or 0x8p-3, depending on what happened to be convenient. This
meant that printing a value as a double and printing the same value
as a long double could produce different (but equivalent) results.
The change is to always make the leading digit a 1, unless the
number is 0. This solves the aforementioned problem and has
several other advantages.
2. Use the FPU to do rounding. This is far simpler and more portable
than manipulating the bits, and it fixes an obsure round-to-even
bug. It also raises the exceptions now required by IEEE 754R.
The drawbacks are that it is usually slightly slower, and it makes
printf less effective as a debugging tool when the FPU is hosed
(e.g., due to a buggy softfloat implementation).
3. On i386, twiddle the rounding precision so that (2) works properly
for long doubles.
4. Make several simplifications that are now possible due to (2).
5. Split __hldtoa() into a separate file.
Thanks to remko for access to a sparc64 box for testing.
flags appropriately. The next step is to make it raise a SIGFPE if
any exceptions are unmasked.
Thanks to remko for access to a sparc64 box for testing.
- fma(x, y, z) returns z, not NaN, if z is infinite, x and y are finite,
x*y overflows, and x*y and z have opposite signs.
- fma(x, y, z) doesn't generate an overflow, underflow, or inexact exception
if z is NaN or infinite, as per IEEE 754R.
- If the rounding mode is set to FE_DOWNWARD, fma(1.0, 0.0, -0.0) is -0.0,
not +0.0.
returns errno, because errno can be mucked by user's signal handler and
most of pthread api heavily depends on errno to be correct, this change
should improve stability of the thread library.
This makes little difference in float precision, but in double
precision gives a speedup of about 30% on amd64 (A64 CPU) and i386
(A64). This depends on fabs[f]() being inline and efficient. The
bit fiddling (or any use of SET_HIGH_WORD(), which libm does too
much because it was best on old 32-bit machines) always causes
packing overheads and sometimes causes stalls in the packing, since
it operates on only part of a variable in the double precision case.
It apparently did cause stalls in a critical path here.
fabs(x+0.0)+fabs(y+0.0) when mixing NaNs. This improves
consistency of the result by making it harder for the compiler to reorder
the operands. (FP addition is not necessarily commutative because the
order of operands makes a difference on some machines iff the operands are
both NaNs.)
__xdrrec_getrec has returned TRUE, then we have a complete request in
the buffer - calling xdrrec_skiprecord is not necessary. In particular,
if there is another record already buffered on the stream,
xdrrec_skiprecord will discard both this request and the next
one, causing the call to xdr_callmsg to fail and the stream to be
closed.
Sponsored by: Isilon Systems
live in libm, while modf() lives in libc due to historical
mistakes. I'm claiming in the manpage that they all live in libm,
since programmers should not rely on the mistake.
