[flang][NFC] use tablegen to create StackArrays constructor (#90038)

Stack arrays needs to stay running only on func.func because it needs to
know which block terminators can end the function (rather than just
branch between unstructured control flow). A similar concept does not
exist at the more abstract level of "any top level mlir operation".

For example, it currently looks for func::ReturnOp and
fir::UnreachableOp as points when execution can end. If this were to be
run on omp.declare_reduction, it would also need to understand
omp.YieldOp (perhaps only when omp.declare_reduction is the parent).
There isn't a generic concept in MLIR for this.

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_STACKARRAYS
 #define GEN_PASS_DECL_LOOPVERSIONING
 #include "flang/Optimizer/Transforms/Passes.h.inc"
 
@@ -59,7 +60,6 @@ createExternalNameConversionPass(bool appendUnderscore);
 std::unique_ptr<mlir::Pass> createMemDataFlowOptPass();
 std::unique_ptr<mlir::Pass> createPromoteToAffinePass();
 std::unique_ptr<mlir::Pass> createMemoryAllocationPass();
-std::unique_ptr<mlir::Pass> createStackArraysPass();
 std::unique_ptr<mlir::Pass> createAliasTagsPass();
 std::unique_ptr<mlir::Pass>
 createAddDebugInfoPass(fir::AddDebugInfoOptions options = {});

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

@@ -257,7 +257,6 @@ def StackArrays : Pass<"stack-arrays", "mlir::ModuleOp"> {
     allocations.
   }];
   let dependentDialects = [ "fir::FIROpsDialect" ];
-  let constructor = "::fir::createStackArraysPass()";
 }
 
 def AddAliasTags : Pass<"fir-add-alias-tags", "mlir::ModuleOp"> {

flang/include/flang/Tools/CLOptions.inc

@@ -258,7 +258,7 @@ inline void createDefaultFIROptimizerPassPipeline(
   pm.addPass(mlir::createCSEPass());
 
   if (pc.StackArrays)
-    pm.addPass(fir::createStackArraysPass());
+    pm.addPass(fir::createStackArrays());
   else
     fir::addMemoryAllocationOpt(pm);
 

flang/lib/Optimizer/Transforms/StackArrays.cpp

@@ -776,7 +776,3 @@ void StackArraysPass::runOnFunc(mlir::Operation *func) {
     signalPassFailure();
   }
 }
-
-std::unique_ptr<mlir::Pass> fir::createStackArraysPass() {
-  return std::make_unique<StackArraysPass>();
-}