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authorJoseph Myers <joseph@codesourcery.com>2013-12-19 13:36:10 +0000
committerJoseph Myers <joseph@codesourcery.com>2013-12-19 13:36:10 +0000
commitf88acd39da2a509081e541b84ecbf204ef20f9e8 (patch)
tree383c0bcce4b3e74c9150d01550e7c412e47981bd /sysdeps/i386/fpu
parentc688b4196014e0162a1ff11120f6c9516be0c6cb (diff)
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Fix x86/x86_64 expm1 inaccuracy near 0 in directed rounding modes (bug 16293).
Bug 16293 is inaccuracy of x86/x86_64 versions of expm1, near 0 in directed rounding modes, that arises from frndint rounding the exponent to 1 or -1 instead of 0, resulting in large cancellation error. This inaccuracy in turn affects other functions such as sinh that use expm1. This patch fixes the problem by setting round-to-nearest mode temporarily around the affected calls to frndint. I don't think this is needed for other uses of frndint, such as in exp itself, as only for expm1 is the cancellation error significant. Tested x86_64 and x86 and ulps updated accordingly. * sysdeps/i386/fpu/e_expl.S (IEEE754_EXPL) [USE_AS_EXPM1L]: Set round-to-nearest mode when using frndint. * sysdeps/i386/fpu/s_expm1.S (__expm1): Likewise. * sysdeps/i386/fpu/s_expm1f.S (__expm1f): Likewise. * sysdeps/x86_64/fpu/e_expl.S (IEEE754_EXPL) [USE_AS_EXPM1L]: Likewise. * math/auto-libm-test-in: Add more tests of expm1. Do not expect sinh test to fail. * math/auto-libm-test-out: Regenerated. * math/libm-test.inc (TEST_COND_x86_64): Remove macro. (TEST_COND_x86): Likewise. (expm1_tonearest_test_data): New array. (expm1_test_tonearest): New function. (expm1_towardzero_test_data): New array. (expm1_test_towardzero): New function. (expm1_downward_test_data): New array. (expm1_test_downward): New function. (expm1_upward_test_data): New array. (expm1_test_upward): New function. (main): Run the new test functions. * sysdeps/i386/fpu/libm-test-ulps: Update. * sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
Diffstat (limited to 'sysdeps/i386/fpu')
-rw-r--r--sysdeps/i386/fpu/e_expl.S15
-rw-r--r--sysdeps/i386/fpu/libm-test-ulps375
-rw-r--r--sysdeps/i386/fpu/s_expm1.S11
-rw-r--r--sysdeps/i386/fpu/s_expm1f.S11
4 files changed, 412 insertions, 0 deletions
diff --git a/sysdeps/i386/fpu/e_expl.S b/sysdeps/i386/fpu/e_expl.S
index af339f0ff4..a8a5e70b07 100644
--- a/sysdeps/i386/fpu/e_expl.S
+++ b/sysdeps/i386/fpu/e_expl.S
@@ -130,9 +130,24 @@ ENTRY(IEEE754_EXPL)
#endif
3: FLDLOG /* 1 log2(base) */
fmul %st(1), %st /* 1 x log2(base) */
+#ifdef USE_AS_EXPM1L
+ /* Set round-to-nearest temporarily. */
+ subl $8, %esp
+ cfi_adjust_cfa_offset (8)
+ fstcw 4(%esp)
+ movl $0xf3ff, %edx
+ andl 4(%esp), %edx
+ movl %edx, (%esp)
+ fldcw (%esp)
+#endif
frndint /* 1 i */
fld %st(1) /* 2 x */
frndint /* 2 xi */
+#ifdef USE_AS_EXPM1L
+ fldcw 4(%esp)
+ addl $8, %esp
+ cfi_adjust_cfa_offset (-8)
+#endif
fld %st(1) /* 3 i */
fldt MO(c0) /* 4 c0 */
fld %st(2) /* 5 xi */
diff --git a/sysdeps/i386/fpu/libm-test-ulps b/sysdeps/i386/fpu/libm-test-ulps
index a471e5fe9f..bb3adcbd67 100644
--- a/sysdeps/i386/fpu/libm-test-ulps
+++ b/sysdeps/i386/fpu/libm-test-ulps
@@ -6092,9 +6092,15 @@ idouble: 1
ifloat: 1
# expm1
+Test "expm1 (-0x1p-64)":
+ildouble: 1
+ldouble: 1
Test "expm1 (-0x2.dp+4)":
ildouble: 1
ldouble: 1
+Test "expm1 (-0x4p-12)":
+ildouble: 1
+ldouble: 1
Test "expm1 (-45.0)":
ildouble: 1
ldouble: 1
@@ -6108,6 +6114,338 @@ Test "expm1 (11356.25)":
ildouble: 1
ldouble: 1
+# expm1_downward
+Test "expm1_downward (-0x1p-100)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (-0x2.ep+4)":
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (-0x4.9p+4)":
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (-0x4.bp+4)":
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (-0x4p-4)":
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (-0x5p+4)":
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (-0x6.4p+4)":
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (0x1p+0)":
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (0x1p-100)":
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (0x1p-32)":
+idouble: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (0x3.2p+4)":
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (0x4p-12)":
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (0x4p-52)":
+idouble: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (0x7.fp+4)":
+ildouble: 1
+ldouble: 1
+Test "expm1_downward (0x8p-32)":
+ildouble: 1
+ldouble: 1
+
+# expm1_tonearest
+Test "expm1_tonearest (-0x1p-64)":
+ildouble: 1
+ldouble: 1
+Test "expm1_tonearest (-0x2.dp+4)":
+ildouble: 1
+ldouble: 1
+Test "expm1_tonearest (-0x4p-12)":
+ildouble: 1
+ldouble: 1
+Test "expm1_tonearest (0x1p+0)":
+ildouble: 1
+ldouble: 1
+Test "expm1_tonearest (0x2.c5c4p+12)":
+ildouble: 1
+ldouble: 1
+
+# expm1_towardzero
+Test "expm1_towardzero (-0x1.2p+4)":
+float: 1
+Test "expm1_towardzero (-0x1.86ap+16)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x1p-100)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x1p-20)":
+ildouble: 2
+ldouble: 2
+Test "expm1_towardzero (-0x1p-32)":
+idouble: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x1p-64)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x2.4p+4)":
+float: 1
+Test "expm1_towardzero (-0x2.5p+4)":
+float: 1
+Test "expm1_towardzero (-0x2.6p+4)":
+double: 1
+float: 1
+Test "expm1_towardzero (-0x2.71p+12)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x2.cp+4)":
+double: 1
+float: 1
+Test "expm1_towardzero (-0x2.dp+4)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x2.ep+4)":
+double: 1
+float: 1
+Test "expm1_towardzero (-0x3.e8p+8)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x4.9p+4)":
+double: 1
+float: 1
+Test "expm1_towardzero (-0x4.ap+4)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x4.bp+4)":
+double: 1
+float: 1
+Test "expm1_towardzero (-0x4.ep+4)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x4.fp+4)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x4p-12)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0x4p-52)":
+idouble: 1
+ildouble: 2
+ldouble: 2
+Test "expm1_towardzero (-0x5p+4)":
+double: 1
+float: 1
+Test "expm1_towardzero (-0x6.4p+4)":
+double: 1
+float: 1
+Test "expm1_towardzero (-0x8p-32)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0xf.ffffffffffff8p+1020)":
+double: 1
+idouble: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0xf.fffffffffffffffp+16380)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (-0xf.fffffp+124)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (0x1p+0)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (0x1p-100)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (0x1p-32)":
+idouble: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (0x3.2p+4)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (0x4p-12)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (0x4p-52)":
+idouble: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (0x7.fp+4)":
+ildouble: 1
+ldouble: 1
+Test "expm1_towardzero (0x8p-32)":
+ildouble: 1
+ldouble: 1
+
+# expm1_upward
+Test "expm1_upward (-0x1.2p+4)":
+float: 1
+Test "expm1_upward (-0x1.86ap+16)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x1p-100)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x1p-20)":
+ildouble: 2
+ldouble: 2
+Test "expm1_upward (-0x1p-32)":
+idouble: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x1p-64)":
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x2.4p+4)":
+float: 1
+Test "expm1_upward (-0x2.5p+4)":
+float: 1
+Test "expm1_upward (-0x2.6p+4)":
+double: 1
+float: 1
+Test "expm1_upward (-0x2.71p+12)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x2.cp+4)":
+double: 1
+float: 1
+Test "expm1_upward (-0x2.dp+4)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x2.ep+4)":
+double: 1
+float: 1
+Test "expm1_upward (-0x3.e8p+8)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x4.9p+4)":
+double: 1
+float: 1
+Test "expm1_upward (-0x4.ap+4)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x4.bp+4)":
+double: 1
+float: 1
+Test "expm1_upward (-0x4.ep+4)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x4.fp+4)":
+double: 1
+float: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x4p-12)":
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0x4p-52)":
+idouble: 1
+ildouble: 2
+ldouble: 2
+Test "expm1_upward (-0x5p+4)":
+double: 1
+float: 1
+Test "expm1_upward (-0x6.4p+4)":
+double: 1
+float: 1
+Test "expm1_upward (-0x8p-32)":
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0xf.ffffffffffff8p+1020)":
+double: 1
+idouble: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0xf.fffffffffffffffp+16380)":
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (-0xf.fffffp+124)":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (0x1.f4p+8)":
+ildouble: 1
+ldouble: 1
+Test "expm1_upward (0x4p-4)":
+ildouble: 1
+ldouble: 1
+
# gamma
Test "gamma (-0.5)":
double: 1
@@ -7773,6 +8111,9 @@ ldouble: 1
Test "sinh_downward (0x1.8p+4)":
ildouble: 1
ldouble: 1
+Test "sinh_downward (0x8p-32)":
+ildouble: 1
+ldouble: 1
Test "sinh_downward (0xcp-4)":
float: 1
ildouble: 1
@@ -7810,6 +8151,9 @@ ldouble: 1
Test "sinh_towardzero (0x1.8p+4)":
ildouble: 1
ldouble: 1
+Test "sinh_towardzero (0x8p-32)":
+ildouble: 1
+ldouble: 1
Test "sinh_towardzero (0xcp-4)":
float: 1
ildouble: 1
@@ -7840,6 +8184,9 @@ ldouble: 1
Test "sinh_upward (0x1.7p+4)":
ildouble: 1
ldouble: 1
+Test "sinh_upward (0x8p-32)":
+double: 1
+float: 1
Test "sinh_upward (0xcp-4)":
float: 1
ildouble: 2
@@ -10663,6 +11010,34 @@ Function: "expm1":
ildouble: 1
ldouble: 1
+Function: "expm1_downward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: "expm1_tonearest":
+ildouble: 1
+ldouble: 1
+
+Function: "expm1_towardzero":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 2
+ldouble: 2
+
+Function: "expm1_upward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 2
+ldouble: 2
+
Function: "gamma":
double: 1
float: 2
diff --git a/sysdeps/i386/fpu/s_expm1.S b/sysdeps/i386/fpu/s_expm1.S
index 91617eb74c..398055276e 100644
--- a/sysdeps/i386/fpu/s_expm1.S
+++ b/sysdeps/i386/fpu/s_expm1.S
@@ -78,7 +78,18 @@ ENTRY(__expm1)
5: fldt MO(l2e) // log2(e) : x
fmulp // log2(e)*x
fld %st // log2(e)*x : log2(e)*x
+ // Set round-to-nearest temporarily.
+ subl $8, %esp
+ cfi_adjust_cfa_offset (8)
+ fstcw 4(%esp)
+ movl $0xf3ff, %ecx
+ andl 4(%esp), %ecx
+ movl %ecx, (%esp)
+ fldcw (%esp)
frndint // int(log2(e)*x) : log2(e)*x
+ fldcw 4(%esp)
+ addl $8, %esp
+ cfi_adjust_cfa_offset (-8)
fsubr %st, %st(1) // int(log2(e)*x) : fract(log2(e)*x)
fxch // fract(log2(e)*x) : int(log2(e)*x)
f2xm1 // 2^fract(log2(e)*x)-1 : int(log2(e)*x)
diff --git a/sysdeps/i386/fpu/s_expm1f.S b/sysdeps/i386/fpu/s_expm1f.S
index 2f1b6f69fc..e5e52a08f3 100644
--- a/sysdeps/i386/fpu/s_expm1f.S
+++ b/sysdeps/i386/fpu/s_expm1f.S
@@ -78,7 +78,18 @@ ENTRY(__expm1f)
5: fldt MO(l2e) // log2(e) : x
fmulp // log2(e)*x
fld %st // log2(e)*x : log2(e)*x
+ // Set round-to-nearest temporarily.
+ subl $8, %esp
+ cfi_adjust_cfa_offset (8)
+ fstcw 4(%esp)
+ movl $0xf3ff, %ecx
+ andl 4(%esp), %ecx
+ movl %ecx, (%esp)
+ fldcw (%esp)
frndint // int(log2(e)*x) : log2(e)*x
+ fldcw 4(%esp)
+ addl $8, %esp
+ cfi_adjust_cfa_offset (-8)
fsubr %st, %st(1) // int(log2(e)*x) : fract(log2(e)*x)
fxch // fract(log2(e)*x) : int(log2(e)*x)
f2xm1 // 2^fract(log2(e)*x)-1 : int(log2(e)*x)