================
@@ -51,28 +57,71 @@ class StringToOffsetTable {
return II->second;
}
- // Emit the string using string literal concatenation, for better readability
- // and searchability.
- void EmitStringLiteralDef(raw_ostream &OS, const Twine &Decl,
- const Twine &Indent = " ") const {
+ // Emit a string table definition with the provided name and indent.
+ //
+ // When possible, this uses string-literal concatenation to emit the string
+ // contents in a readable and searchable way. However, for (very) large
string
+ // tables MSVC cannot reliably use string literals and so there we use a
large
+ // character array. We still use a line oriented emission and add comments to
+ // provide searchability even in this case.
+ //
+ // The string table, and its input string contents, are always emitted as
both
+ // `static` and `constexpr`. Both `Name` and (`Name` + "Storage") must be
+ // valid identifiers to declare.
+ void EmitStringTableDef(raw_ostream &OS, const Twine &Name,
+ const Twine &Indent = "") const {
OS << formatv(R"(
#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Woverlength-strings"
#endif
-{0}{1} = )",
- Indent, Decl);
+{0}static constexpr char {1}Storage[] = )",
+ Indent, Name);
+
+ // MSVC silently miscompiles string literals longer than 64k in some
+ // circumstances. When the string table is longer, emit it as an array of
+ // character literals.
+ bool UseChars = AggregateString.size() > (64 * 1024);
----------------
s-barannikov wrote:
> I don't know the history of why we have two offset table emission systems.
> I can try to consolidate the divergence that his grown between these two if
> necessary, but it's a pretty big undertaking.
`SequenceToOffsetTable` supports arbitrary sequences (e.g. register numbers).
I'm not sure if consolidating them is possible or necessary.
> To me, it seems a simpler model to just unconditionally emit tables larger
> than 64k using the awkward syntax rather than add more tablegen flags that
> change behavior. This lets the vast majority of cases use the simpler form.
This is just two LoC change (declaring the option and using it in the `if`)
that will avoid compile time penalty if the compiler is not MSVC and make the
[large] generated tables readable/searchable. Not a big win probably, so LGTM
as is.
https://github.com/llvm/llvm-project/pull/123548
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