[clang] [BoundsSafety][APINotes] Upstream API notes format for bounds-safety function parameters (PR #185257)

[Connector Switch via cfe-commits]

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@@ -1074,14 +1074,43 @@ void APINotesWriter::Implementation::writeGlobalVariableBlock(
 }
 
 namespace {
+void emitBoundsSafetyInfo(raw_ostream &OS, const BoundsSafetyInfo &BSI) {
+  llvm::support::endian::Writer writer(OS, llvm::endianness::little);
+  uint8_t flags = 0;
+  if (auto kind = BSI.getKind()) {
+    flags |= 0x01;                // 1 bit
+    flags |= (uint8_t)*kind << 1; // 3 bits
+  }
+  flags <<= 4;
+  if (auto level = BSI.getLevel()) {
+    flags |= 0x01;        // 1 bit
+    flags |= *level << 1; // 3 bits
+  }
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c8ef wrote:

For the level I think 3 bits is enough for most use cases. Maybe @hnrklssn can shed more light on this?

https://github.com/llvm/llvm-project/pull/185257