Some, but not all, architectures mix in OS-provided random seeds when
initializing the fastrand state. The others have TODOs saying we need
to do the same. Lift that logic up in the architecture-independent
part, and use memhash to mix the seed instead of a simple addition.
Previously, dumping the fastrand state at initialization would yield
something like the following on linux-amd64, where the values in the
first column do not change between runs (as thread IDs are sequential
and always start at 0), and the values in the second column, while
changing every run, are pretty correlated:
first run:
0x0 0x44d82f1c
0x5f356495 0x44f339de
0xbe6ac92a 0x44f91cd8
0x1da02dbf 0x44fd91bc
0x7cd59254 0x44fee8a4
0xdc0af6e9 0x4547a1e0
0x3b405b7e 0x474c76fc
0x9a75c013 0x475309dc
0xf9ab24a8 0x4bffd075
second run:
0x0 0xa63fc3eb
0x5f356495 0xa6648dc2
0xbe6ac92a 0xa66c1c59
0x1da02dbf 0xa671bce8
0x7cd59254 0xa70e8287
0xdc0af6e9 0xa7129d2e
0x3b405b7e 0xa7379e2d
0x9a75c013 0xa7e4c64c
0xf9ab24a8 0xa7ecce07
With this change, we get initial states that appear to be much more
unpredictable, both within the same run as well as between runs:
0x11bddad7 0x97241c63
0x553dacc6 0x2bcd8523
0x62c01085 0x16413d92
0x6f40e9e6 0x7a138de6
0xa4898053 0x70d816f0
0x5ca5b433 0x188a395b
0x62778ca9 0xd462c3b5
0xd6e160e4 0xac9b4bd
0xb9571d65 0x597a981d
Change-Id: Ib22c530157d74200df0083f830e0408fd4aaea58
Reviewed-on: https://go-review.googlesource.com/c/go/+/203439
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This CL removes runtime code working around missing ARM processor capability
information in the auxiliary vector in older FreeBSD versions.
As announced in the Go 1.12 release notes Go 1.13 will require FreeBSD 11.2+
or FreeBSD 12.0+. These FreeBSD versions support CPU capability detection
through AT_HWCAP and AT_HWCAP2 values stored in the auxiliary vector.
Updates #27619
Change-Id: I2a457b578d35101a7a5fd56ae9b81b300ad17da4
Reviewed-on: https://go-review.googlesource.com/c/go/+/165799
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Yuval Pavel Zholkover <paulzhol@gmail.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Martin Möhrmann <martisch@uos.de>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Assumes mandatory VFP and VFPv3 support to be present by default
but not IDIVA if AT_HWCAP is not available.
Adds GODEBUGCPU options to disable the use of code paths in the runtime
that use hardware support for division.
Change-Id: Ida02311bd9b9701de3fc120697e69445bf6c0853
Reviewed-on: https://go-review.googlesource.com/114826
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
As pointed out by Josh Bleecher Snyder in CL 99780.
The check is for GOARM > 6, so suggest to recompile with either GOARM=5
or GOARM=6.
Change-Id: I6a97e87bdc17aa3932f5c8cb598bba85c3cf4be9
Reviewed-on: https://go-review.googlesource.com/101936
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
AT_HWCAP is not available on FreeBSD-11.1-RELEASE or earlier and the wrong const was used.
Use the correct value, and initialize hwcap with ^uint32(0) inorder not to fail the VFP tests.
Fixes#24507.
Change-Id: I5c3eed57bb53bf992b7de0eec88ea959806306b9
Reviewed-on: https://go-review.googlesource.com/102355
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Decode AT_PAGESZ to determine physPageSize on freebsd/{386,amd64,arm}
and AT_HWCAP for hwcap and hardDiv on freebsd/arm. Also use hwcap to
perform the FP checks in checkgoarm akin to the linux/arm
implementation.
Change-Id: I532810a1581efe66277e4305cb234acdc79ee91e
Reviewed-on: https://go-review.googlesource.com/99780
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The hardware divider is an optional component of ARMv7. This patch
detects whether it is available in runtime and use it or not.
1. The hardware divider is detected at startup and a flag is set/clear
according to a perticular bit of runtime.hwcap.
2. Each call of runtime.udiv will check this flag and decide if
use the hardware division instruction.
A rough test shows the performance improves 40-50% for ARMv7. And
the compatibility of ARMv5/v6 is not broken.
fixes#19118
Change-Id: Ic586bc9659ebc169553ca2004d2bdb721df823ac
Reviewed-on: https://go-review.googlesource.com/37496
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Also, crash early on non-Linux SMP ARM systems when GOARM < 7;
without the proper synchronization, SMP cannot work.
Linux is okay because we call kernel-provided routines for
synchronization and barriers, and the kernel takes care of
providing the right routines for the current system.
On non-Linux systems we are left to fend for ourselves.
It is possible to use different synchronization on GOARM=6,
but it's too late to do that in the Go 1.5 cycle.
We don't believe there are any non-Linux SMP GOARM=6 systems anyway.
Fixes#12067.
Change-Id: I771a556e47893ed540ec2cd33d23c06720157ea3
Reviewed-on: https://go-review.googlesource.com/13363
Reviewed-by: Austin Clements <austin@google.com>
