Spec Reducer (sreducer)

66.  How to reduce a spec test case?
Let us suppose there is a failure in h264ref benchmark.

Step1: create a build, link and run script
basically you need to create a script that just lists the compile commands,
the link command and the run command:
For example: I have a script named /home/jtony/tools/spec_reducer/buildLinkRun.sh
The build and link commands can be found by running the build.dry.sh script, this should
be run in your spec directory (like /home/jtony/scrum/s2/114/spec/cpu2006),

1(a): Here is my build command (part example):
cd /home/jtony/perf-runs/benchspec/CPU2006/464.h264ref/build/build_base_none.0000
/home/jtony/git-llvm/build/team-llvm//bin/clang -c -o annexb.o -DSPEC_CPU -DNDEBUG   -O2         -DSPEC_CPU_LINUX -fsigned-char
annexb.c &
/home/jtony/git-llvm/build/team-llvm//bin/clang -c -o biariencode.o -DSPEC_CPU -DNDEBUG   -O2         -DSPEC_CPU_LINUX -fsigned-char
     biariencode.c &
/home/jtony/git-llvm/build/team-llvm//bin/clang -c -o block.o -DSPEC_CPU -DNDEBUG   -O2         -DSPEC_CPU_LINUX -fsigned-char        b
lock.c &
/home/jtony/git-llvm/build/team-llvm//bin/clang -c -o cabac.o -DSPEC_CPU -DNDEBUG   -O2         -DSPEC_CPU_LINUX -fsigned-char        c
abac.c &
...


1(b): Here is my link command:
/home/jtony/git-llvm/build/team-llvm//bin/clang  -O2    -DSPEC_CPU_LINUX -fsigned-char   annexb.o biariencode.o block.o cabac.o configfile.o context_ini.o decoder.o explicit_gop.o fast_me.o filehandle.o fmo.o header.o image.o intrarefresh.o leaky_bucket.o lencod.o loopFilter.o macroblock.o mb_access.o mbuffer.o memalloc.o mv-search.o nal.o nalu.o nalucommon.o output.o parset.o parsetcommon.o q_matrix.o q_offsets.o ratectl.o rdopt.o rdopt_coding_state.o rdpicdecision.o refbuf.o rtp.o sei.o slice.o transform8x8.o vlc.o weighted_prediction.o specrand.o             -lm       -m64 -Wl,-q  -Wl,-rpath=/home/jtony/git-llvm/build/team-llvm//lib64 -o h264ref


1(c): the run command is a little bit harder to find, but you should be able to piece together the run
command from the speccmds.cmd file  eg:
/home/jtony/perf-runs/temp/benchspec/CPU2006/464.h264ref/run/run_base_test_none.0000/speccmds.cmd
Here is the run command for my case:
cd /home/jtony/perf-runs/benchspec/CPU2006/464.h264ref/run/run_base_test_none.0000
/home/jtony/perf-runs/benchspec/CPU2006/464.h264ref/build/build_base_none.0000/h264ref -d foreman_test_encoder_baseline.cfg > tony.out
specperl /home/jtony/scrum/s2/114/spec/cpu2006/bin/specdiff -m -l 10  --cw  --floatcompare /home/jtony/scrum/s2/114/spec/cpu2006/benchspec/CPU2006/464.h264ref/data/test/output/foreman_test_baseline_encodelog.out > tony.out


Step2, you need a good (no bug) and a bad (contains the bug) compiler. In my case, I have
The bad one   /home/jtony/git-llvm/build/team-llvm/bin/clang++
The good one  /home/jtony/git-llvm/build/good/bin/clang++
run this:
produceBinReduceScript.sh  good_compiler bad_compiler, like:
/home/nemanjai/llvm/Git/llvm-on-power/utils/produceBinReduceScript.sh tony.sh /home/jtony/git-llvm/build/good/bin/clang /home/jtony/git-llvm/build/team-llvm/bin/clang
that produced `ReduceScript.sh`


Step3, once you have the ReduceScript, you can use binary search to find which file is miscompiled. In my case I have 43, you can do the following:
like
./ReduceScript.sh 1 43
./ReduceScript.sh 1 22
./ReduceScript.sh 11 22
./ReduceScript.sh 15 22
./ReduceScript.sh 18 22
./ReduceScript.sh 18 20
./ReduceScript.sh 18 19
./ReduceScript.sh 19 19

Step 4:
go into PPCISelDAGToDAG.cpp
and add:
`"#include "EnvDecider.hpp"`
and add:
#if 1
  static EnvDecider RunMe("INSTANCE");
  if (!(++RunMe))
    return false;
#endif


Step 5:
then you can invoke the script like this (once you know how many there are):
`INSTANCE=1 ./ReduceScript.sh`
and so on and so forth