[llvm] [PGO] Instrument modules with at least a single function definition (PR #93421)

[Pavel Samolysov via llvm-commits]

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+; RUN: opt < %s -passes=pgo-instr-gen -S | FileCheck %s --check-prefix=GEN-COMDAT
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samolisov wrote:

The idea of the test is to check that the assert on line https://github.com/llvm/llvm-project/pull/93421/files#diff-618e0bf5dc7c44fae29843f3be69506a1b0a1409c7f018c61b0acf593f1c4605R408 is never triggered. A module with no global variables (other than the counters inserted during the instrumentation) was prepared to demonstrate that the version variable `__llvm_profile_raw_version` will be generated and it will be inserted in the module just after the corresponding `comdat`. If you think this is a redundant module, I'm going to remove it.

https://github.com/llvm/llvm-project/pull/93421