[llvm-mca] Add pipeline stall events.
This patch introduces a new class named HWStallEvent (see HWEventListener.h),
and updates the event listener interface. A HWStallEvent represents a pipeline
stall caused by the lack of hardware resources. Similarly to HWInstructionEvent,
the event type is an unsigned, and the exact meaning depends on the subtarget.
At the moment, HWStallEvent supports a few generic dispatch events.
The main goals of this patch is to remove the logic that counts dispatch stalls
from the DispatchUnit to the BackendStatistics view.
Previously, DispatchUnit was responsible for counting and classifying dispatch
stall events. With this patch, we delegate the task of counting and classifying
stall events to the listeners (i.e. in our case, it is view
"BackendStatistics"). So, the DispatchUnit doesn't have to do extra
(unnecessary) bookkeeping.
This patch also helps futher simplifying the Backend interface. Now class
BackendStatistics no longer has to query the Backend interface to obtain the
number of dispatch stalls. As a consequence, we can get rid of all the
'getNumXXX()' methods from class Backend.
The long term goal is to remove all the remaining dependencies between the
Backend and the BackendStatistics interface.
Differential Revision: https://reviews.llvm.org/D44621
llvm-svn: 327837
diff --git a/llvm/tools/llvm-mca/BackendStatistics.h b/llvm/tools/llvm-mca/BackendStatistics.h
index 28c3e0d..dacf5b0 100644
--- a/llvm/tools/llvm-mca/BackendStatistics.h
+++ b/llvm/tools/llvm-mca/BackendStatistics.h
@@ -59,6 +59,7 @@
#include "Backend.h"
#include "View.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/Support/raw_ostream.h"
#include <map>
@@ -80,6 +81,10 @@
unsigned NumRetired;
unsigned NumCycles;
+ // Counts dispatch stall events caused by unavailability of resources. There
+ // is one counter for every generic stall kind (see class HWStallEvent).
+ llvm::SmallVector<unsigned, 8> HWStalls;
+
void updateHistograms() {
DispatchGroupSizePerCycle[NumDispatched]++;
IssuedPerCycle[NumIssued]++;
@@ -93,10 +98,7 @@
void printDispatchUnitStatistics(llvm::raw_ostream &OS) const;
void printSchedulerStatistics(llvm::raw_ostream &OS) const;
- void printDispatchStalls(llvm::raw_ostream &OS, unsigned RATStalls,
- unsigned RCUStalls, unsigned SQStalls,
- unsigned LDQStalls, unsigned STQStalls,
- unsigned DGStalls) const;
+ void printDispatchStalls(llvm::raw_ostream &OS) const;
void printRATStatistics(llvm::raw_ostream &OS, unsigned Mappings,
unsigned MaxUsedMappings) const;
void printRCUStatistics(llvm::raw_ostream &OS, const Histogram &Histogram,
@@ -111,7 +113,7 @@
public:
BackendStatistics(const Backend &backend, const llvm::MCSubtargetInfo &sti)
: B(backend), STI(sti), NumDispatched(0), NumIssued(0), NumRetired(0),
- NumCycles(0) {}
+ NumCycles(0), HWStalls(HWStallEvent::LastGenericEvent) {}
void onInstructionEvent(const HWInstructionEvent &Event) override;
@@ -119,10 +121,13 @@
void onCycleEnd(unsigned Cycle) override { updateHistograms(); }
+ void onStallEvent(const HWStallEvent &Event) override {
+ if (Event.Type < HWStallEvent::LastGenericEvent)
+ HWStalls[Event.Type]++;
+ }
+
void printView(llvm::raw_ostream &OS) const override {
- printDispatchStalls(OS, B.getNumRATStalls(), B.getNumRCUStalls(),
- B.getNumSQStalls(), B.getNumLDQStalls(),
- B.getNumSTQStalls(), B.getNumDispatchGroupStalls());
+ printDispatchStalls(OS);
printRATStatistics(OS, B.getTotalRegisterMappingsCreated(),
B.getMaxUsedRegisterMappings());
printDispatchUnitStatistics(OS);