================
@@ -6519,17 +6518,55 @@ static bool SwitchToLookupTable(SwitchInst *SI,
IRBuilder<> &Builder,
SmallDenseMap<PHINode *, Type *> ResultTypes;
SmallVector<PHINode *, 4> PHIs;
- for (SwitchInst::CaseIt E = SI->case_end(); CI != E; ++CI) {
- ConstantInt *CaseVal = CI->getCaseValue();
- if (CaseVal->getValue().slt(MinCaseVal->getValue()))
- MinCaseVal = CaseVal;
- if (CaseVal->getValue().sgt(MaxCaseVal->getValue()))
- MaxCaseVal = CaseVal;
+ SmallVector<ConstantInt *, 8> CaseVals;
+ for (const auto &CI : SI->cases())
+ CaseVals.push_back(CI.getCaseValue());
+
+ // We want to find a range of indexes that will create the minimal table.
+ // When considering overflow, the next indexed value of the maximum signed
+ // integer is the minimum signed integer.
+ llvm::sort(CaseVals, [](const auto *L, const auto *R) {
+ return L->getValue().slt(R->getValue());
+ });
+ auto *CaseValIter = CaseVals.begin();
+ // We start by using the minimum signed integer and maximum signed as the
+ // minimal table. It's the most common case.
+ ConstantInt *BeginCaseVal = *CaseValIter;
+ ConstantInt *EndCaseVal = CaseVals.back();
+ bool RangeOverflow = false;
+ uint64_t MinTableSize = EndCaseVal->getValue()
+ .ssub_ov(BeginCaseVal->getValue(), RangeOverflow)
+ .getLimitedValue() +
+ 1;
+ // If there is no overflow, then this must be the minimal table.
+ if (RangeOverflow) {
----------------
DianQK wrote:
I put it in #73269.
https://github.com/llvm/llvm-project/pull/67885
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