[clang] [llvm] [llvm-profgen] Add Arm SPE branch profile support (PR #223237)

[Sergey Shcherbinin via cfe-commits]

SergeyShch01 wrote:

@snehasish,

> Could you split this to make it easier for humans to review?

Thanks, yes, I will split this into a sequence of four stacked PRs. I plan to adjust the suggested boundaries slightly so that the larger test  files can be divided more evenly between the PRs:

1. Executable range-end analysis and the required base reader hooks.
2. The single-record Arm SPE reader, parser, and taken-state data model.
3. CLI exposure and connection to the existing LBR counter-generation path,  together with the range, symbolization, and target-validation tests.
4. Diagnostics and raw perf.data support, together with the parser,
   not-taken, perfdata, and documentation changes.
   
The first two PRs will contain the permanent foundations. The third PR will make the feature reachable end to end, and the fourth will add diagnostics and the second input provider. This keeps the existing test files intact while splitting the test volume approximately evenly between the last two PRs.

Regarding SVC  - will treat is as a range end.

https://github.com/llvm/llvm-project/pull/223237