[llvm] [PDB] Refactor cache strategy for function symbol lookups (PR #188927)

[Haohai Wen via llvm-commits]

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@@ -355,29 +366,67 @@ SymbolCache::findFunctionSymbolBySectOffset(uint32_t Sect, uint32_t Offset) {
     consumeError(ExpectedModS.takeError());
     return nullptr;
   }
-  CVSymbolArray Syms = ExpectedModS->getSymbolArray();
 
-  // Search for the symbol in this module.
+  // Return empty intervals in AddressToSymbolId from Start to Stop.
+  auto getInsertRanges = [this](uint64_t Start, uint64_t Stop) {
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HaohaiWen wrote:

Yes. this usually return 1 or 0 range.
Two functions can be fully overlapped. This is prevalent especially when ICF is on.
I have never seen two functions range partially overlapped. However I'm not sure whether this is a valid real case.
This algorithm should be efficient for all of those cases.


https://github.com/llvm/llvm-project/pull/188927