Add IR Profile-Guided Optimization (IR PGO) support to the Flang compiler (#136098)

This patch implements IR-based Profile-Guided Optimization support in
Flang through the following flags:

- `-fprofile-generate` for instrumentation-based profile generation

- `-fprofile-use=<dir>/file` for profile-guided optimization

Resolves #74216 (implements IR PGO support phase)

**Key changes:**

- Frontend flag handling aligned with Clang/GCC semantics

- Instrumentation hooks into LLVM PGO infrastructure

- LIT tests verifying:

    - Instrumentation metadata generation

    - Profile loading from specified path

    - Branch weight attribution (IR checks)

**Tests:**

- Added gcc-flag-compatibility.f90 test module verifying:

    -  Flag parsing boundary conditions

    -  IR-level profile annotation consistency

    -  Profile input path normalization rules

- SPEC2006 benchmark results will be shared in comments

For details on LLVM's PGO framework, refer to [Clang PGO
Documentation](https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization).

This implementation was developed by [XSCC Compiler
Team](https://github.com/orgs/OpenXiangShan/teams/xscc).

---------

Co-authored-by: ict-ql <168183727+ict-ql@users.noreply.github.com>
Co-authored-by: Tom Eccles <t@freedommail.info>

1 files changed, 2 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 4193f0a..30aec87c 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -940,7 +940,8 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
     }
   }
 
-  if (CGM.getCodeGenOpts().getProfileInstr() != CodeGenOptions::ProfileNone) {
+  if (CGM.getCodeGenOpts().getProfileInstr() !=
+      llvm::driver::ProfileInstrKind::ProfileNone) {
     switch (CGM.isFunctionBlockedFromProfileInstr(Fn, Loc)) {
     case ProfileList::Skip:
       Fn->addFnAttr(llvm::Attribute::SkipProfile);