[flang][NFC] Use tablegen to create LoopVersioning constructor (#90037)

The pass is currently defined as only considering function arguments as
candidates for the optimization. I would prefer to generalise the pass
for other top level operations only when there is a concrete use case
before making too many assumptions about the current set of top level
operations. Therefore I have not adapted this pass to run on all top
level operations.

Author: tblah

flang/include/flang/Optimizer/Transforms/Passes.h

@@ -47,6 +47,7 @@ namespace fir {
 #define GEN_PASS_DECL_POLYMORPHICOPCONVERSION
 #define GEN_PASS_DECL_OPENACCDATAOPERANDCONVERSION
 #define GEN_PASS_DECL_ADDDEBUGINFO
+#define GEN_PASS_DECL_LOOPVERSIONING
 #include "flang/Optimizer/Transforms/Passes.h.inc"
 
 std::unique_ptr<mlir::Pass> createAffineDemotionPass();
@@ -62,7 +63,6 @@ std::unique_ptr<mlir::Pass> createStackArraysPass();
 std::unique_ptr<mlir::Pass> createAliasTagsPass();
 std::unique_ptr<mlir::Pass>
 createAddDebugInfoPass(fir::AddDebugInfoOptions options = {});
-std::unique_ptr<mlir::Pass> createLoopVersioningPass();
 
 std::unique_ptr<mlir::Pass>
 createMemoryAllocationPass(bool dynOnHeap, std::size_t maxStackSize);

flang/include/flang/Optimizer/Transforms/Passes.td

@@ -321,7 +321,6 @@ def LoopVersioning : Pass<"loop-versioning", "mlir::func::FuncOp"> {
     an array has element sized stride. The element sizes stride allows some
     loops to be vectorized as well as other loop optimizations.
   }];
-  let constructor = "::fir::createLoopVersioningPass()";
   let dependentDialects = [ "fir::FIROpsDialect" ];
 }
 

flang/include/flang/Tools/CLOptions.inc

@@ -253,7 +253,7 @@ inline void createDefaultFIROptimizerPassPipeline(
   }
 
   if (pc.LoopVersioning)
-    pm.addPass(fir::createLoopVersioningPass());
+    pm.addPass(fir::createLoopVersioning());
 
   pm.addPass(mlir::createCSEPass());
 

flang/lib/Optimizer/Transforms/LoopVersioning.cpp

@@ -556,7 +556,3 @@ void LoopVersioningPass::runOnOperation() {
 
   LLVM_DEBUG(llvm::dbgs() << "=== End " DEBUG_TYPE " ===\n");
 }
-
-std::unique_ptr<mlir::Pass> fir::createLoopVersioningPass() {
-  return std::make_unique<LoopVersioningPass>();
-}