[NFC] Use initial-stack-allocations for more data structures (#110544)

This replaces some of the most frequent offenders of using a DenseMap that
cause a malloc, where the typical element-count is small enough to fit in
an initial stack allocation.

Most of these are fairly obvious, one to highlight is the collectOffset
method of GEP instructions: if there's a GEP, of course it's going to have
at least one offset, but every time we've called collectOffset we end up
calling malloc as well for the DenseMap in the MapVector.

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 7659fc6..cfe40f9 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -925,7 +925,7 @@ CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ,
 }
 
 using PredBlockVector = SmallVector<BasicBlock *, 16>;
-using IncomingValueMap = DenseMap<BasicBlock *, Value *>;
+using IncomingValueMap = SmallDenseMap<BasicBlock *, Value *, 16>;
 
 /// Determines the value to use as the phi node input for a block.
 ///
@@ -2467,7 +2467,7 @@ Value *getSalvageOpsForGEP(GetElementPtrInst *GEP, const DataLayout &DL,
                            SmallVectorImpl<Value *> &AdditionalValues) {
   unsigned BitWidth = DL.getIndexSizeInBits(GEP->getPointerAddressSpace());
   // Rewrite a GEP into a DIExpression.
-  MapVector<Value *, APInt> VariableOffsets;
+  SmallMapVector<Value *, APInt, 4> VariableOffsets;
   APInt ConstantOffset(BitWidth, 0);
   if (!GEP->collectOffset(DL, BitWidth, VariableOffsets, ConstantOffset))
     return nullptr;