Merge pull request #11321 from swiftix/devirtualizer-fixes

[sil-devirtualizer] Code clean-up. Simplify the previous patch.

Author: swiftix

lib/SILOptimizer/Utils/Devirtualize.cpp

@@ -17,7 +17,6 @@
 #include "swift/AST/ProtocolConformance.h"
 #include "swift/AST/SubstitutionMap.h"
 #include "swift/AST/Types.h"
-#include "swift/SIL/DebugUtils.h"
 #include "swift/SIL/SILDeclRef.h"
 #include "swift/SIL/SILFunction.h"
 #include "swift/SIL/SILInstruction.h"
@@ -552,44 +551,6 @@ bool swift::canDevirtualizeClassMethod(FullApplySite AI,
   return true;
 }
 
-// Remove any code that follows a I and set the block's
-// terminator to unreachable.
-static bool insertUnreachable(SILInstruction *I, SILBuilder &B) {
-  assert(I);
-  auto NextI = std::next(SILBasicBlock::iterator(I));
-  // Nothing more to do here.
-  if (NextI != I->getParent()->end() && isa<UnreachableInst>(NextI))
-    return false;
-
-  // Collect together all the instructions after this point.
-  llvm::SmallVector<SILInstruction *, 32> ToRemove;
-  for (auto Inst = I->getParent()->rbegin(); &*Inst != I; ++Inst)
-    ToRemove.push_back(&*Inst);
-
-  SILBasicBlock::iterator EndI;
-  for (auto *Inst : ToRemove) {
-    // Replace any still-remaining uses with undef and erase.
-    Inst->replaceAllUsesWithUndef();
-    assert(onlyHaveDebugUses(Inst) && "Cannot erase instruction that is used!");
-    eraseFromParentWithDebugInsts(Inst, EndI);
-  }
-
-  // Add an `unreachable` to be the new terminator for this block.
-  B.setInsertionPoint(I->getParent());
-  B.createUnreachable(ArtificialUnreachableLocation());
-  return true;
-}
-
-/// If this is a call of a NoReturn function and it is not a terminator
-/// instruction, it should be followed by an unreachable instruction.
-static void handleNoReturnFunction(FullApplySite AI, SILBuilder &B) {
-  if (!AI.getSubstCalleeType()->isNoReturnFunction())
-    return;
-  if (!AI.getInstruction() || isa<TermInst>(AI.getInstruction()))
-    return;
-  insertUnreachable(AI.getInstruction(), B);
-}
-
 /// \brief Devirtualize an apply of a class method.
 ///
 /// \p AI is the apply to devirtualize.
@@ -733,17 +694,9 @@ DevirtualizationResult swift::devirtualizeClassMethod(FullApplySite AI,
         Use->set(ResultValue);
       }
     }
-    // Insert unreachable after the old apply instruction if required.
-    // Do not remove the old instruction yet, because it is done later
-    // elsewhere.
-    handleNoReturnFunction(AI, B);
     return std::make_pair(NewAI.getInstruction(), NewAI);
   }
 
-  // Insert unreachable after the old apply instruction if required.
-  // Do not remove the old instruction yet, because it is done later
-  // elsewhere.
-  handleNoReturnFunction(AI, B);
   // We need to return a pair of values here:
   // - the first one is the actual result of the devirtualized call, possibly
   //   casted into an appropriate type. This SILValue may be a BB arg, if it