[PATCH] D55000: [llvm-mca] Return the total number of cycles from method Pipeline::run().

[Andrea Di Biagio via Phabricator via llvm-commits]

andreadb created this revision.
andreadb added reviewers: courbet, orodley, mattd, gchatelet.
Herald added subscribers: gbedwell, tschuett.

If a user only cares about the overall latency, then the best/quickest way is to change method Pipeline::run() so that it returns the total number of cycles to the caller.

When the simulation pipeline is run, the number of cycles (or an error) is returned from method Pipeline::run().
The advantage is that no hardware event listener is needed for computing that latency. So, the whole process should be faster (and simpler - for that particular use case).


https://reviews.llvm.org/D55000

Files:
  tools/llvm-mca/include/Pipeline.h
  tools/llvm-mca/lib/Pipeline.cpp
  tools/llvm-mca/llvm-mca.cpp


Index: tools/llvm-mca/llvm-mca.cpp
===================================================================
--- tools/llvm-mca/llvm-mca.cpp
+++ tools/llvm-mca/llvm-mca.cpp
@@ -240,8 +240,9 @@
 // Returns true on success.
 static bool runPipeline(mca::Pipeline &P) {
   // Handle pipeline errors here.
-  if (auto Err = P.run()) {
-    WithColor::error() << toString(std::move(Err));
+  Expected<unsigned> Cycles = P.run();
+  if (!Cycles) {
+    WithColor::error() << toString(Cycles.takeError());
     return false;
   }
   return true;
Index: tools/llvm-mca/lib/Pipeline.cpp
===================================================================
--- tools/llvm-mca/lib/Pipeline.cpp
+++ tools/llvm-mca/lib/Pipeline.cpp
@@ -35,7 +35,7 @@
   });
 }
 
-Error Pipeline::run() {
+Expected<unsigned> Pipeline::run() {
   assert(!Stages.empty() && "Unexpected empty pipeline found!");
 
   do {
@@ -46,7 +46,7 @@
     ++Cycles;
   } while (hasWorkToProcess());
 
-  return ErrorSuccess();
+  return Cycles;
 }
 
 Error Pipeline::runCycle() {
Index: tools/llvm-mca/include/Pipeline.h
===================================================================
--- tools/llvm-mca/include/Pipeline.h
+++ tools/llvm-mca/include/Pipeline.h
@@ -67,7 +67,10 @@
 public:
   Pipeline() : Cycles(0) {}
   void appendStage(std::unique_ptr<Stage> S);
-  Error run();
+
+  // Returns the total number of simulated cycles.
+  Expected<unsigned> run();
+
   void addEventListener(HWEventListener *Listener);
 };
 } // namespace mca


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