about summary refs log tree commit diff
path: root/sysdeps/x86_64/fpu
diff options
context:
space:
mode:
authorJoseph Myers <joseph@codesourcery.com>2015-09-25 22:29:10 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-09-25 22:29:10 +0000
commit6ace39382120dd0668b2168591611f71b04ac8f3 (patch)
tree2cee18351450bd4f9586f033cae63aa4d1ec8d4d /sysdeps/x86_64/fpu
parent5a9af6376d43b58c6545feb86002812a57956654 (diff)
downloadglibc-6ace39382120dd0668b2168591611f71b04ac8f3.tar.gz
glibc-6ace39382120dd0668b2168591611f71b04ac8f3.tar.xz
glibc-6ace39382120dd0668b2168591611f71b04ac8f3.zip
Fix pow missing underflows (bug 18825).
Similar to various other bugs in this area, pow functions can fail to
raise the underflow exception when the result is tiny and inexact but
one or more low bits of the intermediate result that is scaled down
(or, in the i386 case, converted from a wider evaluation format) are
zero.  This patch forces the exception in a similar way to previous
fixes, thereby concluding the fixes for known bugs with missing
underflow exceptions currently filed in Bugzilla.

Tested for x86_64, x86, mips64 and powerpc.

	[BZ #18825]
	* sysdeps/i386/fpu/i386-math-asm.h (FLT_NARROW_EVAL_UFLOW_NONNAN):
	New macro.
	(DBL_NARROW_EVAL_UFLOW_NONNAN): Likewise.
	(LDBL_CHECK_FORCE_UFLOW_NONNAN): Likewise.
	* sysdeps/i386/fpu/e_pow.S: Use DEFINE_DBL_MIN.
	(__ieee754_pow): Use DBL_NARROW_EVAL_UFLOW_NONNAN instead of
	DBL_NARROW_EVAL, reloading the PIC register as needed.
	* sysdeps/i386/fpu/e_powf.S: Use DEFINE_FLT_MIN.
	(__ieee754_powf): Use FLT_NARROW_EVAL_UFLOW_NONNAN instead of
	FLT_NARROW_EVAL.  Use separate return path for case when first
	argument is NaN.
	* sysdeps/i386/fpu/e_powl.S: Include <i386-math-asm.h>.  Use
	DEFINE_LDBL_MIN.
	(__ieee754_powl): Use LDBL_CHECK_FORCE_UFLOW_NONNAN, reloading the
	PIC register.
	* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Use
	math_check_force_underflow_nonneg.
	* sysdeps/ieee754/flt-32/e_powf.c (__ieee754_powf): Force
	underflow for subnormal result.
	* sysdeps/ieee754/ldbl-128/e_powl.c (__ieee754_powl): Likewise.
	* sysdeps/ieee754/ldbl-128ibm/e_powl.c (__ieee754_powl): Use
	math_check_force_underflow_nonneg.
	* sysdeps/x86/fpu/powl_helper.c (__powl_helper): Use
	math_check_force_underflow.
	* sysdeps/x86_64/fpu/x86_64-math-asm.h
	(LDBL_CHECK_FORCE_UFLOW_NONNAN): New macro.
	* sysdeps/x86_64/fpu/e_powl.S: Include <x86_64-math-asm.h>.  Use
	DEFINE_LDBL_MIN.
	(__ieee754_powl): Use LDBL_CHECK_FORCE_UFLOW_NONNAN.
	* math/auto-libm-test-in: Add more tests of pow.
	* math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps/x86_64/fpu')
-rw-r--r--sysdeps/x86_64/fpu/e_powl.S3
-rw-r--r--sysdeps/x86_64/fpu/x86_64-math-asm.h13
2 files changed, 16 insertions, 0 deletions
diff --git a/sysdeps/x86_64/fpu/e_powl.S b/sysdeps/x86_64/fpu/e_powl.S
index 358abb8dcb..a44c311bb6 100644
--- a/sysdeps/x86_64/fpu/e_powl.S
+++ b/sysdeps/x86_64/fpu/e_powl.S
@@ -18,6 +18,7 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <machine/asm.h>
+#include <x86_64-math-asm.h>
 
 	.section .rodata.cst8,"aM",@progbits,8
 
@@ -59,6 +60,7 @@ minfinity:
 mzero:
 	.byte 0, 0, 0, 0, 0, 0, 0, 0x80
 	ASM_SIZE_DIRECTIVE(minf_mzero)
+DEFINE_LDBL_MIN
 
 #ifdef PIC
 # define MO(op) op##(%rip)
@@ -175,6 +177,7 @@ ENTRY(__ieee754_powl)
 	orl	%edx, %ecx
 	jnz	6b
 	fstp	%st(0)		// ST*x
+	LDBL_CHECK_FORCE_UFLOW_NONNAN
 	ret
 
 	/* y is ±NAN */
diff --git a/sysdeps/x86_64/fpu/x86_64-math-asm.h b/sysdeps/x86_64/fpu/x86_64-math-asm.h
index 07eecf7079..b5482518d7 100644
--- a/sysdeps/x86_64/fpu/x86_64-math-asm.h
+++ b/sysdeps/x86_64/fpu/x86_64-math-asm.h
@@ -46,6 +46,19 @@ ldbl_min:						\
 	fstp	%st(0);				\
 6464:
 
+/* Likewise, but the argument is not a NaN.  */
+#define LDBL_CHECK_FORCE_UFLOW_NONNAN		\
+	fldt	MO(ldbl_min);			\
+	fld	%st(1);				\
+	fabs;					\
+	fcomip	%st(1), %st(0);			\
+	fstp	%st(0);				\
+	jnc 6464f;				\
+	fld	%st(0);				\
+	fmul	%st(0);				\
+	fstp	%st(0);				\
+6464:
+
 /* Likewise, but the argument is nonnegative and not a NaN.  */
 #define LDBL_CHECK_FORCE_UFLOW_NONNEG		\
 	fldt	MO(ldbl_min);			\