[llvm-mca] Rename Backend to Pipeline. NFC.

Summary:
This change renames the Backend and BackendPrinter to Pipeline and PipelinePrinter respectively. 
Variables and comments have also been updated to reflect this change.

The reason for this rename, is to be slightly more correct about what MCA is modeling.  MCA models a Pipeline, which implies some logical sequence of stages. 

Reviewers: andreadb, courbet, RKSimon

Reviewed By: andreadb, courbet

Subscribers: mgorny, javed.absar, tschuett, gbedwell, llvm-commits

Differential Revision: https://reviews.llvm.org/D48496

llvm-svn: 335496
diff --git a/llvm/tools/llvm-mca/llvm-mca.cpp b/llvm/tools/llvm-mca/llvm-mca.cpp
index fb019f1..380cd3f 100644
--- a/llvm/tools/llvm-mca/llvm-mca.cpp
+++ b/llvm/tools/llvm-mca/llvm-mca.cpp
@@ -21,7 +21,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "BackendPrinter.h"
 #include "CodeRegion.h"
 #include "DispatchStage.h"
 #include "DispatchStatistics.h"
@@ -29,6 +28,8 @@
 #include "FetchStage.h"
 #include "InstructionInfoView.h"
 #include "InstructionTables.h"
+#include "Pipeline.h"
+#include "PipelinePrinter.h"
 #include "RegisterFile.h"
 #include "RegisterFileStatistics.h"
 #include "ResourcePressureView.h"
@@ -506,14 +507,14 @@
     mca::Scheduler HWS(SM, LoadQueueSize, StoreQueueSize, AssumeNoAlias);
 
     // Create the pipeline and add stages to it.
-    auto B = llvm::make_unique<mca::Backend>(
+    auto P = llvm::make_unique<mca::Pipeline>(
         Width, RegisterFileSize, LoadQueueSize, StoreQueueSize, AssumeNoAlias);
-    B->appendStage(llvm::make_unique<mca::FetchStage>(IB, S));
-    B->appendStage(llvm::make_unique<mca::DispatchStage>(
-        B.get(), *STI, *MRI, RegisterFileSize, Width, RCU, PRF, HWS));
-    B->appendStage(llvm::make_unique<mca::RetireStage>(B.get(), RCU, PRF));
-    B->appendStage(llvm::make_unique<mca::ExecuteStage>(B.get(), RCU, HWS));
-    mca::BackendPrinter Printer(*B);
+    P->appendStage(llvm::make_unique<mca::FetchStage>(IB, S));
+    P->appendStage(llvm::make_unique<mca::DispatchStage>(
+        P.get(), *STI, *MRI, RegisterFileSize, Width, RCU, PRF, HWS));
+    P->appendStage(llvm::make_unique<mca::RetireStage>(P.get(), RCU, PRF));
+    P->appendStage(llvm::make_unique<mca::ExecuteStage>(P.get(), RCU, HWS));
+    mca::PipelinePrinter Printer(*P);
 
     if (PrintSummaryView)
       Printer.addView(llvm::make_unique<mca::SummaryView>(SM, S, Width));
@@ -543,7 +544,7 @@
           *STI, *IP, S, TimelineMaxIterations, TimelineMaxCycles));
     }
 
-    B->run();
+    P->run();
     Printer.printReport(TOF->os());
   }