nickdesaulniers added inline comments.
================
Comment at: clang/include/clang/Basic/SourceManager.h:697
+ /// FileID lookup.
+ SmallVector<SourceLocation::UIntTy> LocalLocOffsetTable;
----------------
nickdesaulniers wrote:
> `LocalSLocEntryTable` is a vec of `SrcMgr::SLocEntry`. `SrcMgr::SLocEntry`'s
> `Offset` is:
> ```
> static constexpr int OffsetBits = 8 * sizeof(SourceLocation::UIntTy) - 1;
> SourceLocation::UIntTy Offset : OffsetBits;
> ```
> So this is a vector of 32b values vs the 24b values we need. Does packing
> this by declaring a struct improve locality further?
>
> ```
> diff --git a/clang/include/clang/Basic/SourceManager.h
> b/clang/include/clang/Basic/SourceManager.h
> index 70ba85bbe948..518c6ed59120 100644
> --- a/clang/include/clang/Basic/SourceManager.h
> +++ b/clang/include/clang/Basic/SourceManager.h
> @@ -692,9 +692,15 @@ class SourceManager : public
> RefCountedBase<SourceManager> {
> /// Positive FileIDs are indexes into this table. Entry 0 indicates an
> invalid
> /// expansion.
> SmallVector<SrcMgr::SLocEntry, 0> LocalSLocEntryTable;
> +
> + struct SMOffset {
> + SourceLocation::UIntTy Offset : 24;
> + SMOffset (SourceLocation::UIntTy O): Offset(O){}
> + operator SourceLocation::UIntTy() const { return Offset; }
> + };
> /// An in-parallel SlocEntry offset table, merely used for speeding up the
> /// FileID lookup.
> - SmallVector<SourceLocation::UIntTy> LocalLocOffsetTable;
> + SmallVector<SMOffset> LocalLocOffsetTable;
>
> /// The table of SLocEntries that are loaded from other modules.
> ///
> ```
`struct SMOffset { ... } __attribute__((packed));`
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D135440/new/
https://reviews.llvm.org/D135440
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