Fixes #202374. Preserve LLVM function `!prof` metadata for: - `synthetic_function_entry_count` - `function_entry_count` with import GUID operands The importer represents the entry count, count kind, and trailing import GUID operands in a single `#llvm.function_entry_count` attribute, validates malformed operands before mutating the operation, and exports the metadata through `llvm::Function::setEntryCount`. Tests cover import, export, malformed metadata operands, synthetic counts, synthetic counts with trailing operands, import GUID round-tripping, and raw i64 bit-pattern preservation. Checks: - `git diff --check` - `git clang-format --diff origin/main -- ...` - `llvm-as -disable-output` smoke check Codex was used in making this PR.
Multi-Level Intermediate Representation
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