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.

ChangeLog

@@ -1,3 +1,13 @@
+2015-02-24  Joseph Myers  <joseph@codesourcery.com>
+
+	[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.
+
 2015-02-24  Paul Pluzhnikov  <ppluzhnikov@google.com>
 
 	[BZ #17916]

NEWS

@@ -9,9 +9,9 @@ Version 2.22
 
 * The following bugs are resolved with this release:
 
-  4719, 14841, 13064, 14094, 15319, 15467, 15790, 16560, 17269, 17523,
-  17569, 17588, 17792, 17836, 17912, 17916, 17932, 17944, 17949, 17964,
-  17965, 17967, 17969, 17978, 17987, 17991, 17996, 17998, 17999.
+  4719, 14841, 13064, 14094, 15319, 15467, 15790, 16560, 16783, 17269,
+  17523, 17569, 17588, 17792, 17836, 17912, 17916, 17932, 17944, 17949,
+  17964, 17965, 17967, 17969, 17978, 17987, 17991, 17996, 17998, 17999.
 
 * Character encoding and ctype tables were updated to Unicode 7.0.0, using
   new generator scripts contributed by Pravin Satpute and Mike FABIAN (Red

math/libm-test.inc

@@ -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),

sysdeps/i386/fpu/e_scalb.S

@@ -65,8 +65,10 @@ ENTRY(__ieee754_scalb)
 	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)

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)

sysdeps/i386/fpu/e_scalbl.S

@@ -67,8 +67,10 @@ ENTRY(__ieee754_scalbl)
 	fstp	%st
 	fstp	%st
 	andl	$0x8000, %edx
+	andl	$0x0228, %eax
+	cmpl	$0x0028, %eax
+	je	4f
 	andl	$8, %eax
-	jnz	4f
 	shrl	$11, %edx
 	addl	%edx, %eax
 	fldl	MOX(zero_nan, %eax, 1)

sysdeps/x86_64/fpu/e_scalbl.S

@@ -61,8 +61,10 @@ ENTRY(__ieee754_scalbl)
 	fstp	%st
 	fstp	%st
 	andl	$0x8000, %edx
+	andl	$0x0228, %eax
+	cmpl	$0x0028, %eax
+	je	4f
 	andl	$8, %eax
-	jnz	4f
 	shrl	$11, %edx
 	addl	%edx, %eax
 #ifdef PIC