Commit 24ae5ce5 authored by Alina Sbirlea's avatar Alina Sbirlea
Browse files

[MemorySSA] Update Phi creation when inserting a Def. 

MemoryPhis should be added in the IDF of the blocks newly gaining Defs.
This includes the blocks that gained a Phi and the block gaining a Def,
if the block did not have one before.
Resolves PR43427.

llvm-svn: 373505
parent 340406a7

llvm/lib/Analysis/MemorySSAUpdater.cpp

+40 −37
Original line number Diff line number Diff line
@@ -347,12 +347,16 @@ void MemorySSAUpdater::insertDef(MemoryDef *MD, bool RenameUses) { 


    // If this is the first def in the block and this insert is in an arbitrary

    // place, compute IDF and place phis.

    SmallPtrSet<BasicBlock *, 2> DefiningBlocks;



    // If this is the last Def in the block, also compute IDF based on MD, since

    // this may a new Def added, and we may need additional Phis.

    auto Iter = MD->getDefsIterator();

    ++Iter;

    auto IterEnd = MSSA->getBlockDefs(MD->getBlock())->end();

    if (Iter == IterEnd) {

      SmallPtrSet<BasicBlock *, 2> DefiningBlocks;

    if (Iter == IterEnd)

      DefiningBlocks.insert(MD->getBlock());



    for (const auto &VH : InsertedPHIs)

      if (const auto *RealPHI = cast_or_null<MemoryPhi>(VH))

        DefiningBlocks.insert(RealPHI->getBlock());
@@ -367,31 +371,30 @@ void MemorySSAUpdater::insertDef(MemoryDef *MD, bool RenameUses) { 
        MPhi = MSSA->createMemoryPhi(BBIDF);

        NewInsertedPHIs.push_back(MPhi);

      }

        // Add the phis created into the IDF blocks to NonOptPhis, so they are

        // not optimized out as trivial by the call to getPreviousDefFromEnd

        // below. Once they are complete, all these Phis are added to the

        // FixupList, and removed from NonOptPhis inside fixupDefs(). Existing

        // Phis in IDF may need fixing as well, and potentially be trivial

        // before this insertion, hence add all IDF Phis. See PR43044.

      // Add the phis created into the IDF blocks to NonOptPhis, so they are not

      // optimized out as trivial by the call to getPreviousDefFromEnd below.

      // Once they are complete, all these Phis are added to the FixupList, and

      // removed from NonOptPhis inside fixupDefs(). Existing Phis in IDF may

      // need fixing as well, and potentially be trivial before this insertion,

      // hence add all IDF Phis. See PR43044.

      NonOptPhis.insert(MPhi);

    }

    for (auto &MPhi : NewInsertedPHIs) {

      auto *BBIDF = MPhi->getBlock();

      for (auto *Pred : predecessors(BBIDF)) {

        DenseMap<BasicBlock *, TrackingVH<MemoryAccess>> CachedPreviousDef;

          MPhi->addIncoming(getPreviousDefFromEnd(Pred, CachedPreviousDef),

                            Pred);

        MPhi->addIncoming(getPreviousDefFromEnd(Pred, CachedPreviousDef), Pred);

      }

    }



      // Re-take the index where we're adding the new phis, because the above

      // call to getPreviousDefFromEnd, may have inserted into InsertedPHIs.

    // Re-take the index where we're adding the new phis, because the above call

    // to getPreviousDefFromEnd, may have inserted into InsertedPHIs.

    NewPhiIndex = InsertedPHIs.size();

    for (auto &MPhi : NewInsertedPHIs) {

      InsertedPHIs.push_back(&*MPhi);

      FixupList.push_back(&*MPhi);

    }

    }



    FixupList.push_back(MD);

  }

llvm/test/Analysis/MemorySSA/pr43427.ll

0 → 100644
+42 −0
Original line number Diff line number Diff line 
; RUN: opt -disable-output -licm -print-memoryssa -enable-mssa-loop-dependency=true < %s 2>&1 | FileCheck %s



; CHECK-LABEL: @f()

; CHECK: 8 = MemoryPhi(

; CHECK: 7 = MemoryPhi(

; CHECK: 9 = MemoryPhi(

define void @f() {

entry:

  %e = alloca i16, align 1

  br label %lbl1



lbl1:                                             ; preds = %if.else, %cleanup, %entry

  store i16 undef, i16* %e, align 1

  call void @g()

  br i1 undef, label %for.end, label %if.else



for.end:                                          ; preds = %lbl1

  br i1 undef, label %lbl3, label %lbl2



lbl2:                                             ; preds = %lbl3, %for.end

  br label %lbl3



lbl3:                                             ; preds = %lbl2, %for.end

  br i1 undef, label %lbl2, label %cleanup



cleanup:                                          ; preds = %lbl3

  %cleanup.dest = load i32, i32* undef, align 1

  %switch = icmp ult i32 %cleanup.dest, 1

  br i1 %switch, label %cleanup.cont, label %lbl1



cleanup.cont:                                     ; preds = %cleanup

  call void @llvm.lifetime.end.p0i8(i64 1, i8* null)

  ret void



if.else:                                          ; preds = %lbl1

  br label %lbl1

}



declare void @g()



; Function Attrs: argmemonly nounwind willreturn

declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)