[SLP] Emit optimization remarks

The approach I followed was to emit the remark after getTreeCost concludes
that SLP is profitable.  I initially tried emitting them after the
vectorizeRootInstruction calls in vectorizeChainsInBlock but I vaguely
remember missing a few cases for example in HorizontalReduction::tryToReduce.

ORE is placed in BoUpSLP so that it's available from everywhere (notably
HorizontalReduction::tryToReduce).

We use the first instruction in the root bundle as the locator for the remark.
In order to get a sense how far the tree is spanning I've include the size of
the tree in the remark.  This is not perfect of course but it gives you at
least a rough idea about the tree.  Then you can follow up with -view-slp-tree
to really see the actual tree.

llvm-svn: 302811

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/include/llvm/Transforms/Vectorize/SLPVectorizer.h b/llvm/include/llvm/Transforms/Vectorize/SLPVectorizer.h
index 10338f7937e..c514db41623 100644
--- a/llvm/include/llvm/Transforms/Vectorize/SLPVectorizer.h
+++ b/llvm/include/llvm/Transforms/Vectorize/SLPVectorizer.h
@@ -24,6 +24,7 @@
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/DemandedBits.h"
 #include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/OptimizationDiagnosticInfo.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/Function.h"
@@ -59,7 +60,8 @@ public:
   // Glue for old PM.
   bool runImpl(Function &F, ScalarEvolution *SE_, TargetTransformInfo *TTI_,
                TargetLibraryInfo *TLI_, AliasAnalysis *AA_, LoopInfo *LI_,
-               DominatorTree *DT_, AssumptionCache *AC_, DemandedBits *DB_);
+               DominatorTree *DT_, AssumptionCache *AC_, DemandedBits *DB_,
+               OptimizationRemarkEmitter *ORE_);
 
 private:
   /// \brief Collect store and getelementptr instructions and organize them