[llvm-dev] Adapting TableGen

Martin J. O'Riordan via llvm-dev llvm-dev at lists.llvm.org
Thu Jun 16 06:10:04 PDT 2016

I have a large number of instruction patterns that involves a lot of
replication in TableGen.


To reduce this replication I want to use 'foreach', but in this case the
action is operating on 'multiclass' and 'defm'.  Basically I want to make
the following work:


    foreach item = { "ReplA", "ReplB", ... , "ReplZ" } in {

      defm PRE_#item#_POST : BASE_#item#_SUFF<.....>;



Unfortunately TableGen doesn't handle this for 'multiclass' and 'defm', so I
have made adaptations to 'lib/TableGen/TGParser.*' that would allow this to
happen.  In this code I have a variable 'idFragment' that represents the
iteration variable name for the 'foreach' loop.  Next I want to perform the
substation, but I can see how I get the current value to perform the
replacement.  My code is:


    for (ForeachLoop var: Loops) {

      if (var.IterVar->getName() == idFragment) {


but having identified where to perform the replacement, I can't find how to
get the current value to replace 'item' with {e.g. is it 'ReplF'?}


Any hints on how I can do this?  The normal replacement code I find very
hard to follow.






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