Strategy.
0. Implement new classes. Classes doesn't affect anything. They still work with ConstantInt base values at this stage.
1. Fictitious replacement of current ConstantInt case values with ConstantRangesSet. Case ranges set will still hold single value, and ConstantInt *getCaseValue() will return it. But additionally implement new method in SwitchInst that allows to work with case ranges. Currenly I think it should be some wrapper that returns either single value or ConstantRangesSet object.
2. Step-by-step replacement of old "ConstantInt* getCaseValue()" with new alternative. Modify algorithms for all passes that works with SwitchInst. But don't modify LLParser and BitcodeReader/Writer. Still hold single value in each ConstantRangesSet object. On this stage some parts of LLVM will use old-style methods, and some ones new-style.
3. After all getCaseValue() usages will removed and whole LLVM and its clients will work in new style - modify LLParser, Reader and Writer. Remove getCaseValue().
4. Replace ConstantInt*-based case ranges set items with APInt ones.
Currently we are on Zero Stage: New classes.
ConstantRangesSet.
I selected ConstantArrays as case ranges set "holder" object (it is a temporary decision, I'll explain why below). The array items are may be ConstantVectors with single item, and ConstantVectors with two items (that means single number and range respectively).
The ConstantInt will used as basic value representation. It will replaced with APInt then. Of course ConstantArray and ConstantVector will go away after ConstantInt => APInt replacement.
New class mandatory features:
- bool isSatisfies(ConstantInt *V) method (need better name?). Returns true if the given value satisfies this case.
- Case's ranges and values enumeration. In some passes we need to analize each case (SwitchLowering for example).
Factory + unified clusterify.
I also propose to implement the factory that allows to build case object with user friendly way. I called it CRSBuilder by now.
Currenly I implemented the factory that allows add,remove pairs of range+successor. It also allows add existing ConstantRangesSet decompiling it to separated ranges. Factory can emit either clusters set (single case range + successor) or the set of "ConstantRangesSet + Successor" pairs.
So you can use it either as builder for new cases set for SwitchInst, or for clusterification of existing cases set.
Just call Factory.optimize() and it emits optimized and sorted clusters collection for you!
I tested clusterification on SelectionDAGBuilder - it works fine. Don't worry it was not included in this patch. Just new classes.
Factory is a template. There are two params: SuccessorClass and IsReadonly. So you can specify what successor you need (BB or MBB). And you can also restrict your factory to use values in read-only mode (SelectionDAGBuilder need IsReadonly=true). Read-only factory couldn't build the cases ranges.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155464 91177308-0d34-0410-b5e6-96231b3b80d8
