JIT causes segfaults on ARM code

Steps to reproduce:

1. Compile dev branch for qtbase+qtdeclarative+qtgraphicaleffects
2. Disable SKIP_INNERSHADOW_TEST from in qtgraphicaleffects/tests/auto/auto.pro
3. Compile qtgraphicaleffects/tests/auto/
4. Run qtgraphicaleffects/tests/auto/tst_qtgraphicaleffects
   • Reproduces on both apalis-imx6 HW and qemu-environment

Expected outcome:

• Test passes

Actual

• Test crashes (see crashlog.txt)

Workaround:

• Run the test with:
  • QV4_JIT_CALL_THRESHOLD=100 ./tst_qtgraphicaleffects

More information:

• This commit is the first one after which this started happening:

• commit 3658f534cb1947663d29b9db00dcced462674aed
  Author: Erik Verbruggen <erik.verbruggen@qt.io>
  Date:   Tue Nov 14 10:45:06 2017 +0100
  
      V4: Add a baseline JIT
      
      This patch add a JIT back in for all platforms that supported JITting
      before, with the exception of MIPS.
      
      Change-Id: I51bc5ce3a2ac40e0510bd72a563af897c5b60343
      Reviewed-by: Lars Knoll <lars.knoll@qt.io>
  
  

• This bug also is the root cause behind failing qtquickcontrols tests that had to be disabled with 3be9ca58af5a011fdd20a7aba608781865544e01