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authorJoseph Myers <joseph@codesourcery.com>2014-05-23 12:07:50 +0000
committerJoseph Myers <joseph@codesourcery.com>2014-05-23 12:07:50 +0000
commitb72592e75fdecb34e2ac5f931730409a1fb68e8a (patch)
tree9a7f71aecd06da02f507abf536a72a1bcbd69209 /sysdeps/i386
parent2302d679ce8b36854022207b58e554b3e89dd8c7 (diff)
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Fix log10 (1) in round-downward mode (bug 16977).
As with various other issues of this kind, bug 16977 is log10 (1) wrongly returning -0 rather than +0 in round-downward mode because of an implementation effectively in terms of log1p (x - 1). This patch fixes the issue in the same way used for log. Tested x86_64 and x86 and ulps updated accordingly. Also tested for mips64 to confirm a fix was needed for ldbl-128 and to validate that fix (also applied to ldbl-128ibm since that version of logl is essentially the same as the ldbl-128 one). [BZ #16977] * sysdeps/i386/fpu/e_log10.S (__ieee754_log10): Take absolute value when x - 1 is zero. * sysdeps/i386/fpu/e_log10f.S (__ieee754_log10f): Likewise. * sysdeps/i386/fpu/e_log10l.S (__ieee754_log10l): Likewise. * sysdeps/ieee754/ldbl-128/e_log10l.c (__ieee754_log10l): Return 0.0L for an argument of 1.0L. * sysdeps/ieee754/ldbl-128ibm/e_log10l.c (__ieee754_log10l): Likewise. * sysdeps/x86_64/fpu/e_log10l.S (__ieee754_log10l): Take absolute value when x - 1 is zero. * math/libm-test.inc (log10_test): Use ALL_RM_TEST. * sysdeps/i386/fpu/libm-test-ulps: Update. * sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
Diffstat (limited to 'sysdeps/i386')
-rw-r--r--sysdeps/i386/fpu/e_log10.S8
-rw-r--r--sysdeps/i386/fpu/e_log10f.S8
-rw-r--r--sysdeps/i386/fpu/e_log10l.S8
-rw-r--r--sysdeps/i386/fpu/libm-test-ulps24
4 files changed, 45 insertions, 3 deletions
diff --git a/sysdeps/i386/fpu/e_log10.S b/sysdeps/i386/fpu/e_log10.S
index ce6a81abb6..17277084ca 100644
--- a/sysdeps/i386/fpu/e_log10.S
+++ b/sysdeps/i386/fpu/e_log10.S
@@ -46,7 +46,13 @@ ENTRY(__ieee754_log10)
fnstsw // x-1 : x : log10(2)
andb $0x45, %ah
jz 2f
- fstp %st(1) // x-1 : log10(2)
+ fxam
+ fnstsw
+ andb $0x45, %ah
+ cmpb $0x40, %ah
+ jne 5f
+ fabs // log10(1) is +0 in all rounding modes.
+5: fstp %st(1) // x-1 : log10(2)
fyl2xp1 // log10(x)
ret
diff --git a/sysdeps/i386/fpu/e_log10f.S b/sysdeps/i386/fpu/e_log10f.S
index 8c20723555..72a3b88251 100644
--- a/sysdeps/i386/fpu/e_log10f.S
+++ b/sysdeps/i386/fpu/e_log10f.S
@@ -47,7 +47,13 @@ ENTRY(__ieee754_log10f)
fnstsw // x-1 : x : log10(2)
andb $0x45, %ah
jz 2f
- fstp %st(1) // x-1 : log10(2)
+ fxam
+ fnstsw
+ andb $0x45, %ah
+ cmpb $0x40, %ah
+ jne 5f
+ fabs // log10(1) is +0 in all rounding modes.
+5: fstp %st(1) // x-1 : log10(2)
fyl2xp1 // log10(x)
ret
diff --git a/sysdeps/i386/fpu/e_log10l.S b/sysdeps/i386/fpu/e_log10l.S
index cde987b137..45b9c6d21d 100644
--- a/sysdeps/i386/fpu/e_log10l.S
+++ b/sysdeps/i386/fpu/e_log10l.S
@@ -48,7 +48,13 @@ ENTRY(__ieee754_log10l)
fnstsw // x-1 : x : log10(2)
andb $0x45, %ah
jz 2f
- fstp %st(1) // x-1 : log10(2)
+ fxam
+ fnstsw
+ andb $0x45, %ah
+ cmpb $0x40, %ah
+ jne 5f
+ fabs // log10(1) is +0 in all rounding modes.
+5: fstp %st(1) // x-1 : log10(2)
fyl2xp1 // log10(x)
ret
diff --git a/sysdeps/i386/fpu/libm-test-ulps b/sysdeps/i386/fpu/libm-test-ulps
index 946cad489b..1e89284455 100644
--- a/sysdeps/i386/fpu/libm-test-ulps
+++ b/sysdeps/i386/fpu/libm-test-ulps
@@ -1536,6 +1536,30 @@ Function: "log10":
ildouble: 1
ldouble: 1
+Function: "log10_downward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: "log10_towardzero":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: "log10_upward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
Function: "log1p":
ildouble: 1
ldouble: 1