-/// Given a chain of or (||) or and (&&) comparison of a value against a
-/// constant, this will try to recover the information required for a switch
-/// structure.
-/// It will depth-first traverse the chain of comparison, seeking for patterns
-/// like %a == 12 or %a < 4 and combine them to produce a set of integer
-/// representing the different cases for the switch.
-/// Note that if the chain is composed of '||' it will build the set of elements
-/// that matches the comparisons (i.e. any of this value validate the chain)
-/// while for a chain of '&&' it will build the set elements that make the test
-/// fail.
-struct ConstantComparesGatherer {
-
- Value *CompValue; /// Value found for the switch comparison
- Value *Extra; /// Extra clause to be checked before the switch
- SmallVector<ConstantInt *, 8> Vals; /// Set of integers to match in switch
- unsigned UsedICmps; /// Number of comparisons matched in the and/or chain
-
- /// Construct and compute the result for the comparison instruction Cond
- ConstantComparesGatherer(Instruction *Cond, const DataLayout *DL)
- : CompValue(nullptr), Extra(nullptr), UsedICmps(0) {
- gather(Cond, DL);
+
+
+// Try to match Instruction I as a comparison against a constant and populates
+// Vals with the set of value that match (or does not depending on isEQ).
+// Return nullptr on failure, or return the Value the comparison matched against
+// on success
+// CurrValue, if supplied, is the value we want to match against. The function
+// is expected to fail if a match is found but the value compared to is not the
+// one expected. If CurrValue is supplied, the return value has to be either
+// nullptr or CurrValue
+static Value* GatherConstantComparesMatch(Instruction *I,
+ Value *CurrValue,
+ SmallVectorImpl<ConstantInt*> &Vals,
+ const DataLayout *DL,
+ unsigned &UsedICmps,
+ bool isEQ) {
+
+ // If this is an icmp against a constant, handle this as one of the cases.
+ ICmpInst *ICI;
+ ConstantInt *C;
+ if (!((ICI = dyn_cast<ICmpInst>(I)) &&
+ (C = GetConstantInt(I->getOperand(1), DL)))) {
+ return nullptr;