[llvm] r207528 - Add optimization remarks to the loop unroller and vectorizer.

[David Blaikie]

On Tue, Apr 29, 2014 at 7:27 AM, Diego Novillo <dnovillo at google.com> wrote:
> Author: dnovillo
> Date: Tue Apr 29 09:27:31 2014
> New Revision: 207528
>
> URL: http://llvm.org/viewvc/llvm-project?rev=207528&view=rev
> Log:
> Add optimization remarks to the loop unroller and vectorizer.
>
> Summary:
> This calls emitOptimizationRemark from the loop unroller and vectorizer
> at the point where they make a positive transformation. For the
> vectorizer, it reports vectorization and interleave factors. For the
> loop unroller, it reports all the different supported types of
> unrolling.
>
> Subscribers: llvm-commits
>
> Differential Revision: http://reviews.llvm.org/D3456

Test coverage? (I assume we've plumbed the remark stuff through llc so
this can be tested in LLVM directly?)

>
> Modified:
>     llvm/trunk/include/llvm/Analysis/LoopInfo.h
>     llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp
>     llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
>
> Modified: llvm/trunk/include/llvm/Analysis/LoopInfo.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/LoopInfo.h?rev=207528&r1=207527&r2=207528&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Analysis/LoopInfo.h (original)
> +++ llvm/trunk/include/llvm/Analysis/LoopInfo.h Tue Apr 29 09:27:31 2014
> @@ -453,6 +453,31 @@ public:
>
>    void dump() const;
>
> +  /// \brief Return the debug location of the start of this loop.
> +  /// This looks for a BB terminating instruction with a known debug
> +  /// location by looking at the preheader and header blocks. If it
> +  /// cannot find a terminating instruction with location information,
> +  /// it returns an unknown location.
> +  DebugLoc getStartLoc() const {
> +    DebugLoc StartLoc;
> +    BasicBlock *HeadBB;
> +
> +    // Try the pre-header first.
> +    if ((HeadBB = getLoopPreheader()) != nullptr) {
> +      StartLoc = HeadBB->getTerminator()->getDebugLoc();
> +      if (!StartLoc.isUnknown())
> +        return StartLoc;
> +    }
> +
> +    // If we have no pre-header or there are no instructions with debug
> +    // info in it, try the header.
> +    HeadBB = getHeader();
> +    if (HeadBB)
> +      StartLoc = HeadBB->getTerminator()->getDebugLoc();
> +
> +    return StartLoc;
> +  }
> +
>  private:
>    friend class LoopInfoBase<BasicBlock, Loop>;
>    explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
>
> Modified: llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp?rev=207528&r1=207527&r2=207528&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp Tue Apr 29 09:27:31 2014
> @@ -24,6 +24,7 @@
>  #include "llvm/Analysis/ScalarEvolution.h"
>  #include "llvm/IR/BasicBlock.h"
>  #include "llvm/IR/Dominators.h"
> +#include "llvm/IR/LLVMContext.h"
>  #include "llvm/Support/Debug.h"
>  #include "llvm/Support/raw_ostream.h"
>  #include "llvm/Transforms/Utils/BasicBlockUtils.h"
> @@ -228,20 +229,33 @@ bool llvm::UnrollLoop(Loop *L, unsigned
>        (unsigned)GreatestCommonDivisor64(Count, TripMultiple);
>    }
>
> +  // Report the unrolling decision.
> +  DebugLoc LoopLoc = L->getStartLoc();
> +  Function *F = Header->getParent();
> +  LLVMContext &Ctx = F->getContext();
> +
>    if (CompletelyUnroll) {
>      DEBUG(dbgs() << "COMPLETELY UNROLLING loop %" << Header->getName()
>            << " with trip count " << TripCount << "!\n");
> +    Ctx.emitOptimizationRemark(DEBUG_TYPE, *F, LoopLoc,
> +                               Twine("completely unrolled loop with ") +
> +                                   Twine(TripCount) + " iterations");
>    } else {
>      DEBUG(dbgs() << "UNROLLING loop %" << Header->getName()
>            << " by " << Count);
> +    Twine DiagMsg("unrolled loop by a factor of " + Twine(Count));
>      if (TripMultiple == 0 || BreakoutTrip != TripMultiple) {
>        DEBUG(dbgs() << " with a breakout at trip " << BreakoutTrip);
> +      DiagMsg.concat(" with a breakout at trip " + Twine(BreakoutTrip));
>      } else if (TripMultiple != 1) {
>        DEBUG(dbgs() << " with " << TripMultiple << " trips per branch");
> +      DiagMsg.concat(" with " + Twine(TripMultiple) + " trips per branch");
>      } else if (RuntimeTripCount) {
>        DEBUG(dbgs() << " with run-time trip count");
> +      DiagMsg.concat(" with run-time trip count");
>      }
>      DEBUG(dbgs() << "!\n");
> +    Ctx.emitOptimizationRemark(DEBUG_TYPE, *F, LoopLoc, DiagMsg);
>    }
>
>    bool ContinueOnTrue = L->contains(BI->getSuccessor(0));
>
> Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=207528&r1=207527&r2=207528&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
> +++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Tue Apr 29 09:27:31 2014
> @@ -1222,6 +1222,12 @@ struct LoopVectorize : public FunctionPa
>      // Mark the loop as already vectorized to avoid vectorizing again.
>      Hints.setAlreadyVectorized(L);
>
> +    // Report the vectorization decision.
> +    F->getContext().emitOptimizationRemark(
> +        DEBUG_TYPE, *F, L->getStartLoc(),
> +        Twine("vectorized loop (vectorization factor: ") + Twine(VF.Width) +
> +            ", unroll factor: " + Twine(UF) + ")");
> +
>      DEBUG(verifyFunction(*L->getHeader()->getParent()));
>      return true;
>    }
>
>
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