The powerpc hard-float round and roundf functions, both 32-bit and
64-bit, raise spurious "inexact" exceptions for integer arguments from
adding 0.5 and rounding to integer toward zero.
Since these functions already save and restore the rounding mode, it's
natural to make them restore the full floating-point state instead to
fix this bug, which this patch does. The save of the state is moved
after the first floating-point operation on the input so that any
"invalid" exceptions from signaling NaN inputs are properly
preserved. As a consequence of this approach to the fix, "inexact"
for noninteger arguments (disallowed by TS 18661-1 but not by C99/C11,
see bug 15479) is also avoided for these implementations; this is
*not* a general fix for bug 15479 since plenty of other
implementations of various functions still raise spurious "inexact"
for noninteger arguments.
This issue and fix do not apply to builds using power5+ versions of
round and roundf, which use the frin instruction and avoid "inexact"
exceptions that way.
This patch should get hard-float powerpc32 and powerpc64 (default
function implementations) back to a state where test-float and
test-double will pass after ulps regeneration.
Tested for powerpc32 and powerpc64.
[BZ #15479]
[BZ #19238]
* sysdeps/powerpc/powerpc32/fpu/s_round.S (__round): Save
floating-point state after first operation on input. Restore full
state rather than just rounding mode.
* sysdeps/powerpc/powerpc32/fpu/s_roundf.S (__roundf): Likewise.
* sysdeps/powerpc/powerpc64/fpu/s_round.S (__round): Likewise.
* sysdeps/powerpc/powerpc64/fpu/s_roundf.S (__roundf): Likewise.
Similar to bug 19134 for powerpc32, the powerpc64 implementations of
lround, lroundf, llround, llroundf can raise spurious "inexact"
exceptions for integer arguments from adding 0.5 then converting to
integer (this does not apply to the power5+ version for double, which
uses the frin instruction which is defined never to raise "inexact"; I
don't know why power5+ doesn't use that version for float as well).
This patch fixes the bug in a similar way to the powerpc32 bug, by
testing for integers (adding and subtracting 2^52 and comparing with
the value before that addition and subtraction) and not adding 0.5 in
that case.
The powerpc maintainers may wish to look at making power5+ / power6x /
power8 use frin for float lround / llround as well as for double,
unless there's some reason I've missed that this isn't beneficial.
Tested for powerpc64.
[BZ #19235]
* sysdeps/powerpc/powerpc64/fpu/s_llround.S (__llround): Do not
add 0.5 to integer arguments.
* sysdeps/powerpc/powerpc64/fpu/s_llroundf.S (__llroundf):
Likewise.
(.LC2): New object.
Similar to bug 15491 recently fixed for x86_64 / x86, the powerpc
(both powerpc32 and powerpc64) hard-float implementations of
nearbyintf and nearbyint wrongly clear an "inexact" exception that was
raised before the function was called; this shows up as failure of the
test math/test-nearbyint-except added when that bug was fixed. They
also wrongly leave traps on "inexact" disabled if they were enabled
before the function was called.
This patch fixes the bugs similar to how the x86 bug was fixed: saving
and restoring the whole floating-point state, both to restore the
original "inexact" flag state and to restore the original state of
whether traps on "inexact" were enabled. Because there's a convenient
point in the powerpc implementations to save state after any sNaN
arguments will have raised "invalid" but before "inexact" traps need
to be disabled, no special handling for "invalid" is needed as in the
x86 version.
Tested for powerpc64 and powerpc32, where it fixes the
math/test-nearbyint-except failure as well as fixing the new test
math/test-nearbyint-except-2 added by this patch. Also tested for
x86_64 and x86 that the new test passes.
If powerpc experts see a more efficient way of doing this
(e.g. instruction positioning that's better for pipelines on typical
processors) then of course followups optimizing the fix are welcome.
[BZ #19228]
* sysdeps/powerpc/powerpc32/fpu/s_nearbyint.S (__nearbyint): Save
and restore full floating-point state.
* sysdeps/powerpc/powerpc32/fpu/s_nearbyintf.S (__nearbyintf):
Likewise.
* sysdeps/powerpc/powerpc64/fpu/s_nearbyint.S (__nearbyint):
Likewise.
* sysdeps/powerpc/powerpc64/fpu/s_nearbyintf.S (__nearbyintf):
Likewise.
* math/test-nearbyint-except-2.c: New file.
* math/Makefile (tests): Add test-nearbyint-except-2.
Some powerpc64 processors (e5500 core for instance) does not provide the
fsqrt instruction, however current check to use in math_private.h is
__WORDSIZE and _ARCH_PWR4 (ISA 2.02). This is patch change it to use
the compiler flag _ARCH_PPCSQ (which is the same condition GCC uses to
decide whether to generate fsqrt instruction).
It fixes BZ#16576.
The roundl assembly implementation
(sysdeps/powerpc/powerpc64/fpu/s_roundl.S)
returns wrong results for some inputs where first double is a exact
integer and the precision is determined by second long double.
Checking on implementation comments and history, I am very confident the
assembly implementation was based on a version before commit
5c68d40169 that fixes BZ#2423 (Errors in
long double (ldbl-128ibm) rounding functions in glibc-2.4).
By just removing the implementation and make the build select
sysdeps/ieee754/ldbl-128ibm/s_roundl.c instead fixes the failing math.
This fixes 16707.
The nearbyintl assembly implementation
(sysdeps/powerpc/powerpc64/fpu/s_nearbyintl.S)
returns wrong results for some inputs where first double is a exact
integer and the precision is determined by second long double.
Checking on implementation comments and history, I am very confident the
assembly implementation was based on a version before commit
5c68d40169 that fixes BZ#2423 (Errors in
long double (ldbl-128ibm) rounding functions in glibc-2.4).
By just removing the implementation and make the build select
sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c instead fixes the failing
math.
Fixes BZ#16706.
The ceill assembly implementation (sysdeps/powerpc/powerpc64/fpu/s_ceill.S)
returns wrong results for some inputs where first double is a exact
integer and the precision is determined by second long double.
Checking on implementation comments and history, I am very confident the
assembly implementation was based on a version before commit
5c68d40169 that fixes BZ#2423 (Errors in
long double (ldbl-128ibm) rounding functions in glibc-2.4).
By just removing the implementation and make the build select
sysdeps/ieee754/ldbl-128ibm/s_ceill.c instead fixes the failing math.
Fixes BZ#16701.
This patch add a optimized llround/llroundf implementation for POWER8
using the new Move From VSR Doubleword instruction to gains some
cycles from FP to GRP register move.
This patch add a optimized llrint/llrintf implementation for POWER8
using the new Move From VSR Doubleword instruction to gains some
cycles from FP to GRP register move.
This patch add a optimized finite/finitef implementation for POWER8
using the new Move From VSR Doubleword instruction to gains some
cycles from FP to GRP register move.
This patch add a optimized isinf/isinff implementation for POWER8
using the new Move From VSR Doubleword instruction to gains some
cycles from FP to GRP register move.
This patch add a optimized isnan/isnanf implementation for POWER8
using the new Move From VSR Doubleword instruction to gains some
cycles from FP to GRP register move.
The truncl assembly implementation (sysdeps/powerpc/powerpc64/fpu/s_truncl.S)
returns wrong results for some inputs where first double is a exact integer
and the precision is determined by second long double.
Checking on implementation comments and history, I am very confident the
assembly implementation was based on a version before commit
5c68d40169 that fixes BZ#2423 (Errors in
long double (ldbl-128ibm) rounding functions in glibc-2.4).
By just removing the implementation and make the build select
sysdeps/ieee754/ldbl-128ibm/s_truncl.c instead it fixes tgammal
issues regarding wrong result sign.
The branch prediction hints is actually hurts performance in this case.
The assembly implementation make two assumptions: 1. 'fabs (x) < 2^52'
is unlikely and 2. 'x > 0.0' is unlike (if 1. is true). Since it a
general floating point function, expected input is not bounded and then
it is better to let the hardware handle the branches.
* sysdeps/powerpc/powerpc32/fpu/s_lround.S (__lround): Fixed erroneous
result when x is +/-nextafter(+/-0.5,-/+1) i.e. all 1's in the
mantissa.
* sysdeps/powerpc/powerpc32/power4/fpu/s_llround.S (__llround):
Likewise. Also account for when x is an odd number between 2^52
and 2^53-1.
* sysdeps/powerpc/powerpc64/fpu/s_llround.S (__llround): Likewise.
* sysdeps/powerpc/powerpc64/fpu/s_llroundf.S (__llroundf): Likewise.
* math/libm-test.inc (lround_test, llround_test): Added test cases to
detect aforementioned erroneous conditions.
* math/gen-libm-test.pl (parse_args): Take function name for pretty
output as an argument.
(generate_testfile): Pass it the name given in the START macro.
[BZ #2466]
* math/libm-test.inc (llrint_test, llround_test): Fix last change to
protect large-precision cases with [LDBL_MANT_DIG > 100].
(llrint_test_tonearest, llrint_test_towardzero): Likewise.
(llrint_test_downward, llrint_test_upward): Likewise.
2006-03-15 Steven Munroe <sjmunroe@us.ibm.com>
Alan Modra <amodra@bigpond.net.au>
[BZ #2466]
* math/libm-test.inc (llrint_test, llround_test) [TEST_LDOUBLE]:
Add new test values.
(llrint_test_tonearest, llrint_test_towardzero, llrint_test_downward,
llrint_test_upward): New functions.
(main): Call them.
* sysdeps/ieee754/ldbl-128ibm/s_llrintl.c (__llrintl): Handle
rounding that spans doubles in IBM long double format.
* sysdeps/ieee754/ldbl-128ibm/s_llroundl.c (__llroundl): Likewise.
* sysdeps/powerpc/powerpc64/fpu/s_llrintl.S: Removed.
* sysdeps/powerpc/powerpc64/fpu/s_llroundl.S: Removed.
* sysdeps/powerpc/powerpc64/fpu/s_lrintl.S: Removed.
* sysdeps/powerpc/powerpc64/fpu/s_lroundl.S: Removed.
2006-03-16 Roland McGrath <roland@redhat.com>
