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#
#
# Nimrod's Runtime Library
# (c) Copyright 2012 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
# This file implements the Nimrod profiler. The profiler needs support by the
# code generator. The idea is to inject the instruction stream
# with 'nimProfile()' calls. These calls are injected at every loop end
# (except perhaps loops that have no side-effects). At every Nth call a
# stack trace is taken. A stack tace is a list of cstrings.
{.push profiler: off.}
const
MaxTraceLen = 20 # tracking the last 20 calls is enough
type
TStackTrace* = array [0..MaxTraceLen-1, cstring]
TProfilerHook* = proc (st: TStackTrace) {.nimcall.}
proc captureStackTrace(f: PFrame, st: var TStackTrace) =
const
firstCalls = 5
var
it = f
i = 0
total = 0
while it != nil and i <= high(st)-(firstCalls-1):
# the (-1) is for the "..." entry
st[i] = it.procname
inc(i)
inc(total)
it = it.prev
var b = it
while it != nil:
inc(total)
it = it.prev
for j in 1..total-i-(firstCalls-1):
if b != nil: b = b.prev
if total != i:
st[i] = "..."
inc(i)
while b != nil and i <= high(st):
st[i] = b.procname
inc(i)
b = b.prev
const
SamplingInterval = 50_000
# set this to change the default sampling interval
var
profilerHook*: TProfilerHook
## set this variable to provide a procedure that implements a profiler in
## user space. See the `nimprof` module for a reference implementation.
gTicker {.threadvar.}: int
proc callProfilerHook(hook: TProfilerHook) {.noinline.} =
# 'noinline' so that 'nimProfile' does not perform the stack allocation
# in the common case.
var st: TStackTrace
captureStackTrace(framePtr, st)
hook(st)
proc nimProfile() =
## This is invoked by the compiler in every loop and on every proc entry!
if gTicker == 0:
gTicker = -1
if not isNil(profilerHook):
# disable recursive calls: XXX should use try..finally,
# but that's too expensive!
let oldHook = profilerHook
profilerHook = nil
callProfilerHook(oldHook)
profilerHook = oldHook
gTicker = SamplingInterval
dec gTicker
{.pop.}
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