[mlir][OpenMP][NFC] Remove dead uses of OpenMPVarMappingStackFrame (#125061)

This is left over from the old way reductions were implemented.
OpenMPVarMappingStackFrame doesn't actually do anything anymore so these
uses can go away.

Author: tblah

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

@@ -75,21 +75,6 @@ class OpenMPAllocaStackFrame
   llvm::OpenMPIRBuilder::InsertPointTy allocaInsertPoint;
 };
 
-/// ModuleTranslation stack frame containing the partial mapping between MLIR
-/// values and their LLVM IR equivalents.
-class OpenMPVarMappingStackFrame
-    : public LLVM::ModuleTranslation::StackFrameBase<
-          OpenMPVarMappingStackFrame> {
-public:
-  MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID(OpenMPVarMappingStackFrame)
-
-  explicit OpenMPVarMappingStackFrame(
-      const DenseMap<Value, llvm::Value *> &mapping)
-      : mapping(mapping) {}
-
-  DenseMap<Value, llvm::Value *> mapping;
-};
-
 /// Custom error class to signal translation errors that don't need reporting,
 /// since encountering them will have already triggered relevant error messages.
 ///
@@ -1541,12 +1526,6 @@ convertOmpSections(Operation &opInst, llvm::IRBuilderBase &builder,
           isByRef)))
     return failure();
 
-  // Store the mapping between reduction variables and their private copies on
-  // ModuleTranslation stack. It can be then recovered when translating
-  // omp.reduce operations in a separate call.
-  LLVM::ModuleTranslation::SaveStack<OpenMPVarMappingStackFrame> mappingGuard(
-      moduleTranslation, reductionVariableMap);
-
   SmallVector<StorableBodyGenCallbackTy> sectionCBs;
 
   for (Operation &op : *sectionsOp.getRegion().begin()) {
@@ -1940,12 +1919,6 @@ convertOmpWsloop(Operation &opInst, llvm::IRBuilderBase &builder,
   if (failed(convertIgnoredWrappers(loopOp, wsloopOp, moduleTranslation)))
     return failure();
 
-  // Store the mapping between reduction variables and their private copies on
-  // ModuleTranslation stack. It can be then recovered when translating
-  // omp.reduce operations in a separate call.
-  LLVM::ModuleTranslation::SaveStack<OpenMPVarMappingStackFrame> mappingGuard(
-      moduleTranslation, reductionVariableMap);
-
   // Set up the source location value for OpenMP runtime.
   llvm::OpenMPIRBuilder::LocationDescription ompLoc(builder);
 
@@ -2116,12 +2089,6 @@ convertOmpParallel(omp::ParallelOp opInst, llvm::IRBuilderBase &builder,
                               reductionVariableMap, isByRef, deferredStores)))
       return llvm::make_error<PreviouslyReportedError>();
 
-    // Store the mapping between reduction variables and their private copies on
-    // ModuleTranslation stack. It can be then recovered when translating
-    // omp.reduce operations in a separate call.
-    LLVM::ModuleTranslation::SaveStack<OpenMPVarMappingStackFrame> mappingGuard(
-        moduleTranslation, reductionVariableMap);
-
     // Save the alloca insertion point on ModuleTranslation stack for use in
     // nested regions.
     LLVM::ModuleTranslation::SaveStack<OpenMPAllocaStackFrame> frame(