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authorNoah Goldstein <goldstein.w.n@gmail.com>2022-06-15 10:41:29 -0700
committerNoah Goldstein <goldstein.w.n@gmail.com>2022-06-15 14:25:55 -0700
commitb446822b6ae4e8149902a78cdd4a886634ad6321 (patch)
tree417d3ee01f93bd92db817203660b6f8591f625f8 /manual
parent686216945a7873237bf892bbe38a2eef23aadeba (diff)
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x86: Add bounds `x86_non_temporal_threshold`
The lower-bound (16448) and upper-bound (SIZE_MAX / 16) are assumed
by memmove-vec-unaligned-erms.

The lower-bound is needed because memmove-vec-unaligned-erms unrolls
the loop aggressively in the L(large_memset_4x) case.

The upper-bound is needed because memmove-vec-unaligned-erms
right-shifts the value of `x86_non_temporal_threshold` by
LOG_4X_MEMCPY_THRESH (4) which without a bound may overflow.

The lack of lower-bound can be a correctness issue. The lack of
upper-bound cannot.
Diffstat (limited to 'manual')
-rw-r--r--manual/tunables.texi2
1 files changed, 1 insertions, 1 deletions
diff --git a/manual/tunables.texi b/manual/tunables.texi
index 1482412078..2c076019ae 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -47,7 +47,7 @@ glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
 glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
 glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
 glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
-glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x4040, max: 0x0fffffffffffffff)
 glibc.cpu.x86_shstk:
 glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
 glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)