Thread.getStackTrace is slow with clang

We have found Thread.getStackTrace to be much slower (2x) when jvm is built with clang compared to jvm built with gcc.
tested clang versions coming with xcode 6/7/8/9/10
tested gcc versions: 4.9, 6.5
Issue affects jdk11+
Attaching simple test case to reproduce the issue. test case calls Thread.GetStackTrace() 100k times

on my machine results with gcc are 120(+-10) seconds
clang results are varying a lot from run to run between 185 to 230 seconds

To compare apples to apples (gcc vs clang on macos):
To be able to build hotspot( jdk11) with gcc on macos I have made a patch: http://cr.openjdk.java.net/~vkempik/gcc_jdk11_macos/gcc.patch

instructions to build hotspot (libjvm.dylib) on macos 10.14 with gcc:

install xcode 10
install gcc@6 from brew
sudo ln -s /usr/local/bin/gcc-6 /usr/local/bin/gcc
sudo ln -s /usr/local/bin/g++-6 /usr/local/bin/g++
apply provided patch gcc.patch
use these options with configure: --with-toolchain-type=gcc --with-toolchain-path=/usr/local/bin

make hotspot

copy buit libjvm.dylib into lib/server/ folder of same jdk version built with clang