[llvm-dev] Are there any tools to reduce the IR file that caused a problem?

[cszide via llvm-dev]

Hi everyone,
I want to test the passes in llvm, and I got some passes sequences that caused the crash of opt.
Although I can use bugpoint to narrow down the source of problems, I can only get some reduced and 
simplified IR and passes to reproduce the problem. My question is how to get the reduced IR of the original IR
file to reproduce the problem. For example,
"opt a.bc -a -b -c -d (where a, b, c and d are passes)" has a crash problem caused by "-a -b -c -d", so we can use 
bugpoint to narrow down the source of problems, thus bugpoint will tell us "You can reproduce the problem with: 
opt bugpoint-reduced-simplified.bc -c". However, for the "bugpoint-reduced-simplified.bc", I do not know the actual wrong points
of the original "a.bc", and the pass "-c" is good for "a.bc", the actual wrong passes sequence is "-b -c" for "a.bc", i.e., we need to run pass "-b" before 
pass "-c" to reproduce the problem on the original IR file. 
So how to reduce the original IR and get the actual wrong passes sequence? Are there any tools? Or there are some special tips of bugpoint
for this purpose? 
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