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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>
38 lines
1.2 KiB
Go
38 lines
1.2 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import "unsafe"
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var hardDiv bool // TODO: set if a hardware divider is available
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func lwp_mcontext_init(mc *mcontextt, stk unsafe.Pointer, mp *m, gp *g, fn uintptr) {
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// Machine dependent mcontext initialisation for LWP.
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mc.__gregs[_REG_R15] = uint32(funcPC(lwp_tramp))
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mc.__gregs[_REG_R13] = uint32(uintptr(stk))
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mc.__gregs[_REG_R0] = uint32(uintptr(unsafe.Pointer(mp)))
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mc.__gregs[_REG_R1] = uint32(uintptr(unsafe.Pointer(gp)))
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mc.__gregs[_REG_R2] = uint32(fn)
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}
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func checkgoarm() {
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// TODO(minux): FP checks like in os_linux_arm.go.
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// osinit not called yet, so ncpu not set: must use getncpu directly.
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if getncpu() > 1 && goarm < 7 {
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print("runtime: this system has multiple CPUs and must use\n")
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print("atomic synchronization instructions. Recompile using GOARM=7.\n")
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exit(1)
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}
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}
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//go:nosplit
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func cputicks() int64 {
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// Currently cputicks() is used in blocking profiler and to seed runtime·fastrand().
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// runtime·nanotime() is a poor approximation of CPU ticks that is enough for the profiler.
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// TODO: need more entropy to better seed fastrand.
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return nanotime()
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}
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