[clang][HLSL][SPRI-V] Add convergence intrinsics (#80680)

HLSL has wave operations and other kind of function which required the
control flow to either be converged, or respect certain constraints as
where and how to re-converge.

At the HLSL level, the convergence are mostly obvious: the control flow
is expected to re-converge at the end of a scope.
Once translated to IR, HLSL scopes disapear. This means we need a way to
communicate convergence restrictions down to the backend.

For this, the SPIR-V backend uses convergence intrinsics. So this commit
adds some code to generate convergence intrinsics when required.

---------

Signed-off-by: Nathan Gauër <brioche@google.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 8dd6da5..e2a7e28 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -4985,6 +4985,25 @@ public:
   llvm::Value *emitBoolVecConversion(llvm::Value *SrcVec,
                                      unsigned NumElementsDst,
                                      const llvm::Twine &Name = "");
+  // Adds a convergence_ctrl token to |Input| and emits the required parent
+  // convergence instructions.
+  llvm::CallBase *addControlledConvergenceToken(llvm::CallBase *Input);
+
+private:
+  // Emits a convergence_loop instruction for the given |BB|, with |ParentToken|
+  // as it's parent convergence instr.
+  llvm::IntrinsicInst *emitConvergenceLoopToken(llvm::BasicBlock *BB,
+                                                llvm::Value *ParentToken);
+  // Adds a convergence_ctrl token with |ParentToken| as parent convergence
+  // instr to the call |Input|.
+  llvm::CallBase *addConvergenceControlToken(llvm::CallBase *Input,
+                                             llvm::Value *ParentToken);
+  // Find the convergence_entry instruction |F|, or emits ones if none exists.
+  // Returns the convergence instruction.
+  llvm::IntrinsicInst *getOrEmitConvergenceEntryToken(llvm::Function *F);
+  // Find the convergence_loop instruction for the loop defined by |LI|, or
+  // emits one if none exists. Returns the convergence instruction.
+  llvm::IntrinsicInst *getOrEmitConvergenceLoopToken(const LoopInfo *LI);
 
 private:
   llvm::MDNode *getRangeForLoadFromType(QualType Ty);