[mlir][NFC] Mark type converter in `populate...` functions as `const` (#111250)

This commit marks the type converter in `populate...` functions as
`const`. This is useful for debugging.

Patterns already take a `const` type converter. However, some
`populate...` functions 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. Programmers can then conclude from the
function signature that these functions 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.

1 files changed, 1 insertions, 1 deletions

diff --git a/flang/lib/Optimizer/CodeGen/CodeGenOpenMP.cpp b/flang/lib/Optimizer/CodeGen/CodeGenOpenMP.cpp
index 48d6c000e..da13ed6 100644
--- a/flang/lib/Optimizer/CodeGen/CodeGenOpenMP.cpp
+++ b/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);
 }