[flang] Add the MLIR pass pipelines for dumping (#183144)

The flang driver never registered passes in the MLIR pass registry, so
--mlir-print-ir-before=<pass> always failed with `Cannot find option`.

This commit adds pass registration calls before CLI option parsing in
the -mmlir handler such that all ~30 pipeline passes are now selectable.

flang/docs/Overview.md

@@ -180,8 +180,15 @@ perform various optimizations and transformations.  The final pass creates an
 LLVM IR representation of the program.
 
 **Commands:**
-  - `flang -mmlir --mlir-print-ir-after-all -S src.f90` dumps the FIR code after each pass to standard error
   - `flang -fc1 -emit-llvm src.f90` dumps the LLVM IR to src.ll
+  - `flang -mmlir --mlir-print-ir-after-all -S src.f90` dumps the FIR code after each pass to standard error
+  - `flang -mmlir --mlir-print-ir-before=<pass> -S src.f90` dumps the FIR code before a specific pass to standard error
+  - `flang -mmlir --mlir-print-ir-after=<pass> -S src.f90` dumps the FIR code after a specific pass to standard error
+
+Note: The exact set of passes depends on compilation options.  For example,
+`stack-arrays` only appears when `-fstack-arrays` is enabled.  To see the
+complete list for a given compilation, use `--mlir-print-ir-before-all` and
+look at the `IR Dump Before` headers.
 
 ## Object code generation and linking
 

flang/include/flang/Optimizer/Passes/Pipelines.h

@@ -117,6 +117,10 @@ void addLLVMDialectToLLVMPass(mlir::PassManager &pm, llvm::raw_ostream &output);
 /// Use inliner extension point callback to register the default inliner pass.
 void registerDefaultInlinerPass(MLIRToLLVMPassPipelineConfig &config);
 
+/// Register the passes used in Flang's MLIR pass pipeline
+/// e.g. --mlir-print-ir-before=<pass> and similar.
+void registerFlangPipelinePasses();
+
 /// Create a pass pipeline for running default optimization passes for
 /// incremental conversion of FIR.
 ///

flang/lib/FrontendTool/CMakeLists.txt

@@ -8,6 +8,7 @@ add_flang_library(flangFrontendTool
 
   LINK_LIBS
   flangFrontend
+  flangPasses
 
   LINK_COMPONENTS
   Option

flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp

@@ -18,6 +18,7 @@
 #include "flang/Frontend/CompilerInstance.h"
 #include "flang/Frontend/FrontendActions.h"
 #include "flang/Frontend/FrontendPluginRegistry.h"
+#include "flang/Optimizer/Passes/Pipelines.h"
 
 #include "mlir/IR/AsmState.h"
 #include "mlir/IR/MLIRContext.h"
@@ -207,6 +208,8 @@ bool executeCompilerInvocation(CompilerInstance *flang) {
 
   // Honor -mmlir. This should happen AFTER plugins have been loaded!
   if (!flang->getFrontendOpts().mlirArgs.empty()) {
+    fir::registerFlangPipelinePasses(); // Must be called before
+                                        // mlir::registerPassManagerCLOptions()
     mlir::registerMLIRContextCLOptions();
     mlir::registerPassManagerCLOptions();
     mlir::registerAsmPrinterCLOptions();

flang/lib/Optimizer/Passes/CMakeLists.txt

@@ -7,6 +7,7 @@ add_flang_library(flangPasses
 
   LINK_LIBS
   FIRCodeGen
+  FIROpenACCTransforms
   FIRTransforms
   FlangOpenMPTransforms
   FortranSupport
@@ -18,6 +19,10 @@ add_flang_library(flangPasses
   MLIR_LIBS
   ${dialect_libs}
   ${extension_libs}
+  MLIRComplexToStandard
+  MLIRLLVMIRTransforms
+  MLIRMathToFuncs
+  MLIRMathToLLVM
   MLIRPass
   MLIRReconcileUnrealizedCasts
   MLIRSCFToControlFlow

flang/lib/Optimizer/Passes/Pipelines.cpp

@@ -10,6 +10,9 @@
 /// common to flang and the test tools.
 
 #include "flang/Optimizer/Passes/Pipelines.h"
+#include "flang/Optimizer/OpenACC/Passes.h"
+#include "mlir/Conversion/Passes.h"
+#include "mlir/Dialect/LLVMIR/Transforms/Passes.h"
 #include "llvm/Support/CommandLine.h"
 
 /// Force setting the no-alias attribute on fuction arguments when possible.
@@ -459,4 +462,31 @@ void createMLIRToLLVMPassPipeline(mlir::PassManager &pm,
   });
 }
 
+/// Register the passes used in flang's MLIR pass pipeline so that
+/// --mlir-print-ir-before=<pass> and --mlir-print-ir-after=<pass> work.
+/// Must be called BEFORE mlir::registerPassManagerCLOptions() because
+/// that function creates the PassNameCLParser which snapshots the pass
+/// registry during initialization.
+void registerFlangPipelinePasses() {
+  // MLIR core passes used in the pipeline.
+  mlir::registerCSEPass();
+  mlir::registerCanonicalizerPass();
+  mlir::registerInlinerPass();
+
+  // MLIR conversion passes used in the pipeline.
+  mlir::registerSCFToControlFlowPass();
+  mlir::registerConvertMathToFuncs();
+  mlir::registerConvertComplexToStandardPass();
+  mlir::registerConvertMathToLLVMPass();
+  mlir::LLVM::registerLLVMAddComdats();
+  mlir::registerReconcileUnrealizedCastsPass();
+
+  // FIR, HLFIR, and OpenMP passes.
+  fir::registerOptCodeGenPasses();
+  fir::registerOptTransformPasses();
+  hlfir::registerHLFIRPasses();
+  flangomp::registerFlangOpenMPPasses();
+  fir::acc::registerFIROpenACCPasses();
+}
+
 } // namespace fir

flang/test/Driver/mmlir-print-ir.f90

@@ -0,0 +1,13 @@
+! Verify that --mlir-print-ir-before=<pass> and --mlir-print-ir-after=<pass>
+! work for registered passes.
+
+! RUN: %flang_fc1 -emit-llvm -mmlir --mlir-print-ir-before=cse -o /dev/null %s 2>&1 | FileCheck %s --check-prefix=BEFORE
+! RUN: %flang_fc1 -emit-llvm -mmlir --mlir-print-ir-after=cse -o /dev/null %s 2>&1 | FileCheck %s --check-prefix=AFTER
+
+! BEFORE: IR Dump Before CSE
+! BEFORE: func.func @_QQmain
+
+! AFTER: IR Dump After CSE
+! AFTER: func.func @_QQmain
+
+end program

flang/test/Fir/print-ir-pass.fir

@@ -0,0 +1,15 @@
+// Verify that --mlir-print-ir-before and --mlir-print-ir-after work in fir-opt
+// for FIR/HLFIR-specific passes registered by registerFlangPipelinePasses().
+
+// RUN: fir-opt --convert-hlfir-to-fir --mlir-print-ir-before=convert-hlfir-to-fir %s -o /dev/null 2>&1 | FileCheck %s --check-prefix=BEFORE
+// RUN: fir-opt --convert-hlfir-to-fir --mlir-print-ir-after=convert-hlfir-to-fir %s -o /dev/null 2>&1 | FileCheck %s --check-prefix=AFTER
+
+// BEFORE: IR Dump Before ConvertHLFIRtoFIR
+// BEFORE: func.func @dummy()
+
+// AFTER: IR Dump After ConvertHLFIRtoFIR
+// AFTER: func.func @dummy()
+
+func.func @dummy() {
+  return
+}

flang/tools/fir-opt/CMakeLists.txt

@@ -28,6 +28,7 @@ target_link_libraries(fir-opt PRIVATE
   FlangOpenMPTransforms
   FIRAnalysis
   MIFDialect
+  flangPasses
   ${test_libs}
 )
 

flang/tools/fir-opt/fir-opt.cpp

@@ -16,6 +16,7 @@
 #include "flang/Optimizer/HLFIR/Passes.h"
 #include "flang/Optimizer/OpenACC/Passes.h"
 #include "flang/Optimizer/OpenMP/Passes.h"
+#include "flang/Optimizer/Passes/Pipelines.h"
 #include "flang/Optimizer/Support/InitFIR.h"
 #include "flang/Optimizer/Transforms/Passes.h"
 
@@ -37,11 +38,7 @@ void registerTestOpenACC();
 
 int main(int argc, char **argv) {
   fir::support::registerMLIRPassesForFortranTools();
-  fir::registerOptCodeGenPasses();
-  fir::registerOptTransformPasses();
-  hlfir::registerHLFIRPasses();
-  flangomp::registerFlangOpenMPPasses();
-  fir::acc::registerFIROpenACCPasses();
+  fir::registerFlangPipelinePasses();
 #ifdef FLANG_INCLUDE_TESTS
   fir::test::registerTestFIRAliasAnalysisPass();
   fir::test::registerTestFIROpenACCInterfacesPass();
@@ -52,6 +49,6 @@ int main(int argc, char **argv) {
   fir::support::registerDialects(registry);
   registry.insert<mlir::memref::MemRefDialect>();
   fir::support::addFIRExtensions(registry);
-  return failed(MlirOptMain(argc, argv, "FIR modular optimizer driver\n",
-      registry));
+  return failed(
+      MlirOptMain(argc, argv, "FIR modular optimizer driver\n", registry));
 }