Pass -fno-omit-frame-pointer to fix stack walking.

Brendan Gregg's page points out this issue.  Some people are annoyed
that this because part of the amd64 ABI.

benchmarks/perf.sh

@@ -7,6 +7,21 @@ set -o nounset
set -o pipefail
set -o errexit

# TODO:
# - kernel symbols.  Is that why there are a lot of [unknown] in opt mode?
# - grep for call_function in collapsed.  I don't see it?
#   - it's inlined I guess?

# Question: PyEval_EvalFrameEx doesn't appear recursive in opt mode?  At least
# according to 'perf'.  Or maybe you don't have enough samples to catch it?

# NOTES:
# - dbg vs. opt matters a lot
# - function-level performance categorization is bad for bytecode interpreters,
#   which have a single function and a big switch statement.
# - a longer file like configure-coreutils hit garbage collection!  collect()
# - reference counting functions: visit_decref, visit_reachable

install() {
  # linux-tools-generic is the kernel module
  # Apparently you need a package specific to the kernel, not sure why.
@@ -75,11 +90,15 @@ _record() {
  # everything is PyEval_EvalFrameEx.
  local flag='-g'
  local bin=_bin/oil.ovm-opt 
  #local bin=_bin/oil.ovm-dbg  # This shows more details

  local freq=1000  # 1000 Hz

  #local file=benchmarks/testdata/abuild  # small file

  # This shows more details
  #local bin=_bin/oil.ovm-dbg
  local file=benchmarks/testdata/configure-coreutils  # big file

  perf record $flag -o perf.data -- $bin osh --ast-format none -n benchmarks/testdata/abuild
  time perf record $flag -F $freq -o perf.data -- $bin osh --ast-format none -n $file
  #perf record -o perf.data -- _bin/osh --ast-format none -n benchmarks/testdata/abuild
}
record() { sudo $0 _record; }
@@ -95,14 +114,14 @@ report() {
  perf report -n --stdio "$@"
}

_perf-data() {
_make-readable() {
  # This gets run as root
  chmod 644 perf.data
  chown andy perf.data
  file perf.data
  ls -l perf.data
}
perf-data() { sudo $0 _perf-data; }
make-readable() { sudo $0 _make-readable; }

# Wow 11 billion instructions!  9 billion cycles.  2.3 billion branches.  Crazy.
# Only 21M branch misses, or 0.9%.  Interesting.

build/compile.sh

@@ -248,7 +248,11 @@ build-dbg() {

# This will be stripped later.
build-opt() {
  build "$@" -O3
  # frame pointer for perf.  Otherwise stack traces are messed up!
  # http://www.brendangregg.com/FlameGraphs/cpuflamegraphs.html#C  But why
  # isn't debuginfo enough?  Because it's a recursive function?
  # Does this make things slower?  Do I need a "perf" build?
  build "$@" -O3 -fno-omit-frame-pointer
}

#