Nanojit test coverage

On i386, Nanojit has two basic modes of operation:  SSE, and non-SSE.  Non-SSE is for old machines that don’t support SSE instructions.  (It might actually be SSE2 instructions, I’m not sure.)  My two machines both support SSE and so the non-SSE is never exercised unless I specify the environment variable X86_FORCE_SSE=no.  Since this invocation doesn’t exactly roll off the fingertips, I don’t do it often.  It’s also easy to mistype, in which case the normal SSE code will be run but I probably won’t notice and so I’m testing something different to what I think I am testing.

I recently committed a patch (bug 516348) that broke the non-SSE mode.  (It may have also broken the SSE mode, but in a less obvious way.)  Whenever I land a patch that breaks something, I try to work out if I could have avoided the breakage through a better process.  In this case I could have, through automation.  I now have the following set of aliases and functions in my .bashrc:

alias jstt_prefix="python trace-test/"
JSTTARGS32="--no-slow -f -x sunspider/check-date-format-tofte.js"

alias jsdtt32="                   jstt_prefix debug32/js $JSTTARGS32"
alias jsott32="                   jstt_prefix opt32/js   $JSTTARGS32"
alias jsdtt32b="X86_FORCE_SSE2=no jstt_prefix debug32/js $JSTTARGS32"
alias jsott32b="X86_FORCE_SSE2=no jstt_prefix opt32/js   $JSTTARGS32"
alias jsott64="                   jstt_prefix opt64/js   $JSTTARGS64"
alias jsdtt64="                   jstt_prefix debug64/js $JSTTARGS64"

function jsatt
  if [ -d debug32 ] && [ -d debug64 ] && [ -d opt32 ] && [ -d opt64 ] ; then
    cd debug32 && mq && cd .. && \
    cd debug64 && mq && cd .. && \
    cd opt32 && mq && cd .. && \
    cd opt64 && mq && cd ..

    if [ $? -eq 0 ] ; then
      echo "debug32"          && jsdtt32   && echo
      echo "debug32 (no SSE)" && jsdtt32b  && echo
      echo "debug64"          && jsdtt64   && echo
      echo "opt32"            && jsott32   && echo
      echo "opt32 (no SSE)"   && jsott32b  && echo
      echo "opt64"            && jsott64   && echo
    echo "missing one of debug32/debug64/opt32/opt64"

The code is boring.  For those reading closely, it relies on the fact that I always put different builds in the directories debug32/, opt32/, debug64/, opt64/.  And I skip check-data-format-tofte.js because it fails if you’re in a non-US timezone, see bug 515214.

I already had ‘jsdtt32’ et al, each of which tests a single configuration.  But now with a single command ‘jsatt’ (which is short for “JavaScript All trace-tests”) I can run the JS trace-tests on 6 different configurations on a single x86-64 machine: 32-bit debug (SSE), 32-bit debug (non-SSE), 64-bit debug, 32-bit optimised (SSE), 32-bit optimised (non-SSE), 64-bit optimised.  And it builds them to make sure they’re all up-to-date.

It’s only a small process change for me, but it means that it’s unlikely I will break any of these configurations in the future, or at least, not in a way that shows up in the trace-tests.

2 replies on “Nanojit test coverage”

You might consider gathering some statistics on how many people actually use the non-SSE mode. Why not just not bother JITting on non-SSE processors?

Unfortunately removing the non-SSE support is not viable at the moment. Nanojit is shared with Adobe, and non-SSE support is currently a requirement for them. One day it hopefully won’t be 🙂

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