diff mbox

Fix x86/x86_64 scalb (qNaN, -Inf) (bug 16783) [committed]

Message ID alpine.DEB.2.10.1502241730230.5398@digraph.polyomino.org.uk
State Committed
Headers

Commit Message

Joseph Myers Feb. 24, 2015, 5:30 p.m. UTC 
  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.

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.
diff mbox

Patch

diff --git a/math/libm-test.inc b/math/libm-test.inc
index ffdc153..b3396b6 100644
--- a/math/libm-test.inc
+++ b/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),
diff --git a/sysdeps/i386/fpu/e_scalb.S b/sysdeps/i386/fpu/e_scalb.S
index 20d489e..6a01aa6 100644
--- a/sysdeps/i386/fpu/e_scalb.S
+++ b/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)
diff --git a/sysdeps/i386/fpu/e_scalbf.S b/sysdeps/i386/fpu/e_scalbf.S
index b6dd021..12b2515 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)
diff --git a/sysdeps/i386/fpu/e_scalbl.S b/sysdeps/i386/fpu/e_scalbl.S
index 83f17b2..d10b22e 100644
--- a/sysdeps/i386/fpu/e_scalbl.S
+++ b/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)
diff --git a/sysdeps/x86_64/fpu/e_scalbl.S b/sysdeps/x86_64/fpu/e_scalbl.S
index c422d53..331bee5 100644
--- a/sysdeps/x86_64/fpu/e_scalbl.S
+++ b/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