[mlir][NFC] Mark type converter in populate... functions as const

This commit marks the type converter in `populate...` functions as `const`. This is useful for debugging. Patterns already take a `const` type converter, but some `populate...` patterns do not only add new patterns, but also add additional type conversion rules. That makes it difficult to find the place where a type conversion was added in the code base. With this change, all `populate...` functions that only populate pattern now have a `const` type converter, from which programmers can conclude that they do not register any new type conversion rules.

Also some minor cleanups around the 1:N dialect conversion infrastructure, which did not always pass the type converter as a `const` object internally.

Author: matthias-springer

flang/include/flang/Optimizer/CodeGen/CodeGen.h

@@ -72,9 +72,9 @@ std::unique_ptr<mlir::Pass> createLLVMDialectToLLVMPass(
         [](llvm::Module &m, llvm::raw_ostream &out) { m.print(out, nullptr); });
 
 /// Populate the given list with patterns that convert from FIR to LLVM.
-void populateFIRToLLVMConversionPatterns(fir::LLVMTypeConverter &converter,
-                                         mlir::RewritePatternSet &patterns,
-                                         fir::FIRToLLVMPassOptions &options);
+void populateFIRToLLVMConversionPatterns(
+    const fir::LLVMTypeConverter &converter, mlir::RewritePatternSet &patterns,
+    fir::FIRToLLVMPassOptions &options);
 
 /// Populate the pattern set with the PreCGRewrite patterns.
 void populatePreCGRewritePatterns(mlir::RewritePatternSet &patterns,

flang/include/flang/Optimizer/CodeGen/CodeGenOpenMP.h

@@ -19,7 +19,7 @@ class LLVMTypeConverter;
 /// dialect, utilised in cases where the default OpenMP dialect handling cannot
 /// handle all cases for intermingled fir types and operations.
 void populateOpenMPFIRToLLVMConversionPatterns(
-    LLVMTypeConverter &converter, mlir::RewritePatternSet &patterns);
+    const LLVMTypeConverter &converter, mlir::RewritePatternSet &patterns);
 
 } // namespace fir
 

flang/include/flang/Optimizer/Transforms/CufOpConversion.h

@@ -22,7 +22,7 @@ class DataLayout;
 
 namespace cuf {
 
-void populateCUFToFIRConversionPatterns(fir::LLVMTypeConverter &converter,
+void populateCUFToFIRConversionPatterns(const fir::LLVMTypeConverter &converter,
                                         mlir::DataLayout &dl,
                                         mlir::RewritePatternSet &patterns);
 

flang/lib/Optimizer/CodeGen/CodeGen.cpp

@@ -3823,7 +3823,7 @@ fir::createLLVMDialectToLLVMPass(llvm::raw_ostream &output,
 }
 
 void fir::populateFIRToLLVMConversionPatterns(
-    fir::LLVMTypeConverter &converter, mlir::RewritePatternSet &patterns,
+    const fir::LLVMTypeConverter &converter, mlir::RewritePatternSet &patterns,
     fir::FIRToLLVMPassOptions &options) {
   patterns.insert<
       AbsentOpConversion, AddcOpConversion, AddrOfOpConversion,

flang/lib/Optimizer/CodeGen/CodeGenOpenMP.cpp

@@ -93,6 +93,6 @@ struct MapInfoOpConversion
 } // namespace
 
 void fir::populateOpenMPFIRToLLVMConversionPatterns(
-    LLVMTypeConverter &converter, mlir::RewritePatternSet &patterns) {
+    const LLVMTypeConverter &converter, mlir::RewritePatternSet &patterns) {
   patterns.add<MapInfoOpConversion>(converter);
 }

flang/lib/Optimizer/Transforms/CufOpConversion.cpp

@@ -222,7 +222,7 @@ struct CufAllocOpConversion : public mlir::OpRewritePattern<cuf::AllocOp> {
   using OpRewritePattern::OpRewritePattern;
 
   CufAllocOpConversion(mlir::MLIRContext *context, mlir::DataLayout *dl,
-                       fir::LLVMTypeConverter *typeConverter)
+                       const fir::LLVMTypeConverter *typeConverter)
       : OpRewritePattern(context), dl{dl}, typeConverter{typeConverter} {}
 
   mlir::LogicalResult
@@ -311,7 +311,7 @@ struct CufAllocOpConversion : public mlir::OpRewritePattern<cuf::AllocOp> {
 
 private:
   mlir::DataLayout *dl;
-  fir::LLVMTypeConverter *typeConverter;
+  const fir::LLVMTypeConverter *typeConverter;
 };
 
 struct CufFreeOpConversion : public mlir::OpRewritePattern<cuf::FreeOp> {
@@ -583,7 +583,7 @@ class CufOpConversion : public fir::impl::CufOpConversionBase<CufOpConversion> {
 } // namespace
 
 void cuf::populateCUFToFIRConversionPatterns(
-    fir::LLVMTypeConverter &converter, mlir::DataLayout &dl,
+    const fir::LLVMTypeConverter &converter, mlir::DataLayout &dl,
     mlir::RewritePatternSet &patterns) {
   patterns.insert<CufAllocOpConversion>(patterns.getContext(), &dl, &converter);
   patterns.insert<CufAllocateOpConversion, CufDeallocateOpConversion,

mlir/docs/Bufferization.md

@@ -651,7 +651,7 @@ is very small, and follows the basic pattern of any dialect conversion pass.
 
 ```
 void mlir::populateTensorBufferizePatterns(
-    BufferizeTypeConverter &typeConverter, RewritePatternSet &patterns) {
+    const BufferizeTypeConverter &typeConverter, RewritePatternSet &patterns) {
   patterns.add<BufferizeCastOp, BufferizeExtractOp>(typeConverter,
                                                     patterns.getContext());
 }

mlir/include/mlir/Conversion/AMDGPUToROCDL/AMDGPUToROCDL.h

@@ -24,7 +24,7 @@ class Pass;
 /// Note: The ROCDL target does not support the LLVM bfloat type at this time
 /// and so this function will add conversions to change all `bfloat` uses
 /// to `i16`.
-void populateAMDGPUToROCDLConversionPatterns(LLVMTypeConverter &converter,
+void populateAMDGPUToROCDLConversionPatterns(const LLVMTypeConverter &converter,
                                              RewritePatternSet &patterns,
                                              amdgpu::Chipset chipset);
 

mlir/include/mlir/Conversion/ArithToLLVM/ArithToLLVM.h

@@ -22,7 +22,7 @@ class Pass;
 #include "mlir/Conversion/Passes.h.inc"
 
 namespace arith {
-void populateArithToLLVMConversionPatterns(LLVMTypeConverter &converter,
+void populateArithToLLVMConversionPatterns(const LLVMTypeConverter &converter,
                                            RewritePatternSet &patterns);
 
 void registerConvertArithToLLVMInterface(DialectRegistry &registry);

mlir/include/mlir/Conversion/ArithToSPIRV/ArithToSPIRV.h

@@ -22,7 +22,7 @@ class Pass;
 #include "mlir/Conversion/Passes.h.inc"
 
 namespace arith {
-void populateArithToSPIRVPatterns(SPIRVTypeConverter &typeConverter,
+void populateArithToSPIRVPatterns(const SPIRVTypeConverter &typeConverter,
                                   RewritePatternSet &patterns);
 
 std::unique_ptr<OperationPass<>> createConvertArithToSPIRVPass();