[PATCH] D103297: [LLD][COFF] Reduce the maximum size of the GHASH table

[Alexandre Ganea via Phabricator via llvm-commits]

aganea created this revision.
aganea added reviewers: rnk, akhuang.
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Before this patch, the maximum size of the GHASH table was `2^31` buckets. However we were storing the bucket index into a `TypeIndex` which has an input limit of `(2^31)-4095` indices, see this link <https://github.com/llvm/llvm-project/blob/d480f968ad8b56d3ee4a6b6df5532d485b0ad01e/llvm/include/llvm/DebugInfo/CodeView/TypeIndex.h#L123>. Any value above that limit will improperly set the `TypeIndex`'s high bit, which is interpreted as `DecoratedItemIdMask`. This used to cause bad indices on extraction when calling `TypeIndex::toArrayIndex()`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D103297

Files:
  lld/COFF/DebugTypes.cpp


Index: lld/COFF/DebugTypes.cpp
===================================================================
--- lld/COFF/DebugTypes.cpp
+++ lld/COFF/DebugTypes.cpp
@@ -1069,7 +1069,8 @@
 
   // Cap the table size so that we can use 32-bit cell indices. Type indices are
   // also 32-bit, so this is an inherent PDB file format limit anyway.
-  tableSize = std::min(size_t(INT32_MAX), tableSize);
+  tableSize =
+      std::min(size_t(INT32_MAX) - TypeIndex::FirstNonSimpleIndex, tableSize);
   ghashState.table.init(static_cast<uint32_t>(tableSize));
 
   // Insert ghashes in parallel. During concurrent insertion, we cannot observe


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