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Fix x86/x86_64 scalb (qNaN, -Inf) (bug 16783).

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Various x86 / x86_64 versions of scalb / scalbf / scalbl produce
spurious "invalid" exceptions for (qNaN, -Inf) arguments, because this
is wrongly handled like (+/-Inf, -Inf) which *should* raise such an
exception.  (In fact the NaN case of the code determining whether to
quietly return a zero or a NaN for second argument -Inf was
accidentally dead since the code had been made to return a NaN with
exception.)  This patch fixes the code to do the proper test for an
infinity as distinct from a NaN.

(Since the existing code does nothing to distinguish qNaNs and sNaNs
here, this patch doesn't either.  If in future we systematically
implement proper sNaN semantics following TS 18661-1:2014, there will
be lots of bugs to address - Thomas found lots of issues with his
patch <https://sourceware.org/ml/libc-ports/2013-04/msg00008.html> to
add SNaN tests (which never went in and would now require significant
reworking).)

Tested for x86_64 and x86.  Committed.

	[BZ #16783]
	* sysdeps/i386/fpu/e_scalb.S (__ieee754_scalb): Do not handle
	arguments (NaN, -Inf) the same as (+/-Inf, -Inf).
	* sysdeps/i386/fpu/e_scalbf.S (__ieee754_scalbf): Likewise.
	* sysdeps/i386/fpu/e_scalbl.S (__ieee754_scalbl): Likewise.
	* sysdeps/x86_64/fpu/e_scalbl.S (__ieee754_scalbl): Likewise.
	* math/libm-test.inc (scalb_test_data): Add more tests.
This commit is contained in:
Joseph Myers
2015-02-24 17:30:02 +00:00
parent 6909d27675
commit 9438b237ab
7 changed files with 27 additions and 7 deletions
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2
math/libm-test.inc
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@ -9139,6 +9139,8 @@ static const struct test_ff_f_data scalb_test_data[] =
TEST_ff_f (scalb, 0, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_ff_f (scalb, qnan_value, plus_infty, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_ff_f (scalb, plus_infty, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_ff_f (scalb, qnan_value, minus_infty, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_ff_f (scalb, minus_infty, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_ff_f (scalb, qnan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_ff_f (scalb, max_value, max_value, plus_oflow, OVERFLOW_EXCEPTION|ERRNO_PLUS_OFLOW),