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authorSzabolcs Nagy <nsz@port70.net>2013-09-05 12:23:44 +0000
committerSzabolcs Nagy <nsz@port70.net>2013-09-05 12:23:44 +0000
commit02343946215a7ae03634c6490abcc69da68df589 (patch)
treefe6fc02037922375ec8ef1e52da576a3345beb54 /src/math
parente5937885de3c8d493a9d2978aa46a771740c7458 (diff)
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math: fix expm1l on x86_64 (avoid underflow for large negative x)
copy the fix from i386: return -1 instead of exp2l(x)-1 when x <= -65
Diffstat (limited to 'src/math')
-rw-r--r--src/math/x86_64/ceill.s2
-rw-r--r--src/math/x86_64/exp2l.s12
-rw-r--r--src/math/x86_64/truncl.s2
3 files changed, 13 insertions, 3 deletions
diff --git a/src/math/x86_64/ceill.s b/src/math/x86_64/ceill.s
index bc29f15c..f5cfa3b3 100644
--- a/src/math/x86_64/ceill.s
+++ b/src/math/x86_64/ceill.s
@@ -1 +1 @@
-# see floor.s
+# see floorl.s
diff --git a/src/math/x86_64/exp2l.s b/src/math/x86_64/exp2l.s
index e7145881..0d6cd563 100644
--- a/src/math/x86_64/exp2l.s
+++ b/src/math/x86_64/exp2l.s
@@ -4,8 +4,18 @@ expm1l:
fldt 8(%rsp)
fldl2e
fmulp
+ movl $0xc2820000,-4(%rsp)
+ flds -4(%rsp)
+ fucomp %st(1)
+ fnstsw %ax
+ sahf
fld1
- fld %st(1)
+ jb 1f
+ # x*log2e <= -65, return -1 without underflow
+ fstp %st(1)
+ fchs
+ ret
+1: fld %st(1)
fabs
fucom %st(1)
fnstsw %ax
diff --git a/src/math/x86_64/truncl.s b/src/math/x86_64/truncl.s
index bc29f15c..f5cfa3b3 100644
--- a/src/math/x86_64/truncl.s
+++ b/src/math/x86_64/truncl.s
@@ -1 +1 @@
-# see floor.s
+# see floorl.s