[llvm] [ThinLTO]Record import type in GlobalValueSummary::GVFlags (PR #87597)

[Mingming Liu via llvm-commits]

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@@ -737,6 +737,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(live);
   KEYWORD(dsoLocal);
   KEYWORD(canAutoHide);
+  KEYWORD(importAsDec);
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minglotus-6 wrote:

Basically, one-bit serves the purpose to include the global-value-summary entry in the postlink combined summary, and indexing step can selectively set the bit since it has visibility of the combined summary. 

If the one-bit indicates definition, postlink will import function definition along with attributes if function doesn't exist. If the one-bit indicates declaration, postlink can annotate attributes according to summaries if declaration already exists, and use IRMover to import declarations that don't exist yet.

https://github.com/llvm/llvm-project/pull/87597