[flang][debug] Run AddDebugInfo before TargetRewrite.

This help us generate debug info that better represents the actual
Fortran source code.

Fixes #108711.

Author: abidh

flang/lib/Optimizer/Passes/Pipelines.cpp

@@ -264,10 +264,10 @@ void createDefaultFIRCodeGenPassPipeline(mlir::PassManager &pm,
   addNestedPassToAllTopLevelOperations(pm, fir::createAbstractResultOpt);
   fir::addCodeGenRewritePass(
       pm, (config.DebugInfo != llvm::codegenoptions::NoDebugInfo));
+  fir::createDebugPasses(pm, config.DebugInfo, config.OptLevel, inputFilename);
   fir::addTargetRewritePass(pm);
   fir::addCompilerGeneratedNamesConversionPass(pm);
   fir::addExternalNameConversionPass(pm, config.Underscoring);
-  fir::createDebugPasses(pm, config.DebugInfo, config.OptLevel, inputFilename);
 
   if (config.VScaleMin != 0)
     pm.addPass(fir::createVScaleAttr({{config.VScaleMin, config.VScaleMax}}));

flang/test/Driver/mlir-debug-pass-pipeline.f90

@@ -111,10 +111,10 @@
 
 ! ALL-NEXT: CodeGenRewrite
 ! ALL-NEXT:   (S) 0 num-dce'd - Number of operations eliminated
+! DEBUG-NEXT: AddDebugInfo
+! NO-DEBUG-NOT: AddDebugInfo
 ! ALL-NEXT: TargetRewrite
 ! ALL-NEXT: CompilerGeneratedNamesConversion
 ! ALL-NEXT: ExternalNameConversion
-! DEBUG-NEXT: AddDebugInfo
-! NO-DEBUG-NOT: AddDebugInfo
 ! ALL: FIRToLLVMLowering
 ! ALL-NOT: LLVMIRLoweringPass