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authorJoseph Myers <joseph@codesourcery.com>2015-02-24 17:30:02 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-02-24 17:30:02 +0000
commit9438b237abca11de201dd10483717299eafb1f0b (patch)
treeeb70d51aaa288f93cb7f365c2221dc1c08343ad7 /sysdeps/i386/fpu/e_scalbf.S
parent6909d2767580b680138a6aa49aabf4976770e9f6 (diff)
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Fix x86/x86_64 scalb (qNaN, -Inf) (bug 16783).
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.
Diffstat (limited to 'sysdeps/i386/fpu/e_scalbf.S')
-rw-r--r--sysdeps/i386/fpu/e_scalbf.S4
1 files changed, 3 insertions, 1 deletions
diff --git a/sysdeps/i386/fpu/e_scalbf.S b/sysdeps/i386/fpu/e_scalbf.S
index b6dd02122a..12b25159ac 100644
--- a/sysdeps/i386/fpu/e_scalbf.S
+++ b/sysdeps/i386/fpu/e_scalbf.S
@@ -67,8 +67,10 @@ ENTRY(__ieee754_scalbf)
 	fstp	%st
 	fstp	%st
 	andl	$0x80000000, %edx
+	andl	$0x0228, %eax
+	cmpl	$0x0028, %eax
+	je	4f
 	andl	$8, %eax
-	jnz	4f
 	shrl	$27, %edx
 	addl	%edx, %eax
 	fldl	MOX(zero_nan, %eax, 1)