[LoopInterchange] Add stats counter for number of interchanged loops.

[samparker]

LGTM

[fhahn]

rebased

[fhahn]

Thanks for having a look Sam!

Just realized the test case depends on D45208. I will probably wait with submitting it a bit.

[fhahn]

Remove dependency on D45208

llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp

 // This Pass handles loop interchange transform.
 // This pass interchanges loops to provide a more cache-friendly memory access
 // patterns.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/DependenceAnalysis.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/IR/BasicBlock.h"

 #include <cassert>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "loop-interchange"
 
+STATISTIC(LoopsInterchanged, "Number of loops interchanged");
+
 static cl::opt<int> LoopInterchangeCostThreshold(
     "loop-interchange-threshold", cl::init(0), cl::Hidden,
     cl::desc("Interchange if you gain more than this number"));
 
 namespace {
 
 using LoopVector = SmallVector<Loop *, 8>;
 
ORE->emit([&]() {
                                 InnerLoop->getHeader())
              << "Loop interchanged with enclosing loop.";
     });
 
     LoopInterchangeTransform LIT(OuterLoop, InnerLoop, SE, LI, DT,
                                  LoopNestExit, LIL.hasInnerLoopReduction());
     LIT.transform();
     DEBUG(dbgs() << "Loops interchanged.\n");
+    LoopsInterchanged++;
     return true;
   }
 };
 
 } // end anonymous namespace
 
 bool LoopInterchangeLegality::areAllUsesReductions(Instruction *Ins, Loop *L) {
   return llvm::none_of(Ins->users(), [=](User *U) -> bool {

llvm/trunk/test/Transforms/LoopInterchange/call-instructions.ll

-; RUN: opt < %s -basicaa -loop-interchange -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -verify-loop-info -verify-dom-info
+; RUN: opt < %s -basicaa -loop-interchange -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -S \
+; RUN:     -stats 2>&1 | FileCheck -check-prefix=STATS %s
 ; RUN: FileCheck --input-file=%t %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @A = common global [100 x [100 x i32]] zeroinitializer
 
 declare void @foo(i64 %a)
for1.inc10:
   br i1 %exitcond26, label %for1.loopexit, label %for1.header
 
 for1.loopexit:
   br label %exit
 
 exit:
   ret void
 }
+
+; Check stats, we interchanged 1 out of 2 loops.
+; STATS: 1 loop-interchange - Number of loops interchanged