[llvm] Limit Alloca->LDS promotion based on speculations as to eventual register pressure (PR #152814)

[Tim Gymnich via llvm-commits]

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@@ -100,6 +106,14 @@ class AMDGPUPromoteAllocaImpl {
   unsigned VGPRBudgetRatio;
   unsigned MaxVectorRegs;
 
+  std::unordered_map<BasicBlock *, std::unordered_set<Instruction *>>
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tgymnich wrote:

Depending on density of your map one could use `getNumber()` on `BasicBlock` to get a unique number for mapping.
E.g. this could be a SmallVector of sets with a size of F.getMaxBlockNumber().
For the set I'd suggest using a `SmallPtrSet` instead.

https://github.com/llvm/llvm-project/pull/152814