SIL: Don't create witness table declarations when creating new SIL instructions

Another simplification made possible by the change to
SILModule::lookUpWitnessTable().

Author: slavapestov

lib/SIL/SILInstructions.cpp

@@ -312,14 +312,6 @@ VarDecl *DebugValueAddrInst::getDecl() const {
   return getLoc().getAsASTNode<VarDecl>();
 }
 
-static void declareWitnessTable(SILModule &Mod,
-                                ProtocolConformanceRef conformanceRef) {
-  if (conformanceRef.isAbstract()) return;
-  auto C = conformanceRef.getConcrete();
-  if (!Mod.lookUpWitnessTable(C, false))
-    Mod.createWitnessTableDeclaration(C);
-}
-
 AllocExistentialBoxInst *AllocExistentialBoxInst::create(
     SILDebugLocation Loc, SILType ExistentialType, CanType ConcreteType,
     ArrayRef<ProtocolConformanceRef> Conformances,
@@ -331,8 +323,6 @@ AllocExistentialBoxInst *AllocExistentialBoxInst::create(
   SILModule &Mod = F->getModule();
   auto Size = totalSizeToAlloc<swift::Operand>(TypeDependentOperands.size());
   auto Buffer = Mod.allocateInst(Size, alignof(AllocExistentialBoxInst));
-  for (ProtocolConformanceRef C : Conformances)
-    declareWitnessTable(Mod, C);
   return ::new (Buffer) AllocExistentialBoxInst(Loc,
                                                 ExistentialType,
                                                 ConcreteType,
@@ -1631,7 +1621,6 @@ WitnessMethodInst::create(SILDebugLocation Loc, CanType LookupType,
   auto Size = totalSizeToAlloc<swift::Operand>(TypeDependentOperands.size());
   auto Buffer = Mod.allocateInst(Size, alignof(WitnessMethodInst));
 
-  declareWitnessTable(Mod, Conformance);
   return ::new (Buffer) WitnessMethodInst(Loc, LookupType, Conformance, Member,
                                           Ty, TypeDependentOperands);
 }
@@ -1665,8 +1654,6 @@ InitExistentialAddrInst *InitExistentialAddrInst::create(
       totalSizeToAlloc<swift::Operand>(1 + TypeDependentOperands.size());
   void *Buffer = Mod.allocateInst(size,
                                   alignof(InitExistentialAddrInst));
-  for (ProtocolConformanceRef C : Conformances)
-    declareWitnessTable(Mod, C);
   return ::new (Buffer) InitExistentialAddrInst(Loc, Existential,
                                                 TypeDependentOperands,
                                                 ConcreteType,
@@ -1686,9 +1673,6 @@ InitExistentialValueInst *InitExistentialValueInst::create(
       totalSizeToAlloc<swift::Operand>(1 + TypeDependentOperands.size());
 
   void *Buffer = Mod.allocateInst(size, alignof(InitExistentialRefInst));
-  for (ProtocolConformanceRef C : Conformances)
-    declareWitnessTable(Mod, C);
-
   return ::new (Buffer)
       InitExistentialValueInst(Loc, ExistentialType, ConcreteType, Instance,
                                 TypeDependentOperands, Conformances);
@@ -1709,9 +1693,6 @@ InitExistentialRefInst::create(SILDebugLocation Loc, SILType ExistentialType,
 
   void *Buffer = Mod.allocateInst(size,
                                   alignof(InitExistentialRefInst));
-  for (ProtocolConformanceRef C : Conformances)
-    declareWitnessTable(Mod, C);
-
   return ::new (Buffer) InitExistentialRefInst(Loc, ExistentialType,
                                                ConcreteType,
                                                Instance,
@@ -1744,9 +1725,6 @@ InitExistentialMetatypeInst *InitExistentialMetatypeInst::create(
       1 + TypeDependentOperands.size(), conformances.size());
 
   void *buffer = M.allocateInst(size, alignof(InitExistentialMetatypeInst));
-  for (ProtocolConformanceRef conformance : conformances)
-    declareWitnessTable(M, conformance);
-
   return ::new (buffer) InitExistentialMetatypeInst(
       Loc, existentialMetatypeType, metatype,
       TypeDependentOperands, conformances);

lib/SIL/SILVerifier.cpp

@@ -2493,8 +2493,6 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
       auto conformance = AMI->getConformance().getConcrete();
       require(conformance->getType()->isEqual(AMI->getLookupType()),
               "concrete type lookup requires conformance that matches type");
-      require(AMI->getModule().lookUpWitnessTable(conformance, false),
-              "Could not find witness table for conformance");
     }
 
     require(AMI->getMember().requiresNewWitnessTableEntry(),
@@ -3204,13 +3202,6 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
       require(conformances[i].getRequirement() == protocols[i]->getDecl(),
               "init_existential instruction must have conformances in "
               "proper order");
-
-      if (conformances[i].isConcrete()) {
-        auto conformance = conformances[i].getConcrete();
-        require(F.getModule().lookUpWitnessTable(conformance, false),
-                "Could not find witness table for conformance.");
-
-      }
     }
   }
 

test/SILOptimizer/dead_witness_module.swift

@@ -12,4 +12,4 @@ import TestModule
 
 testit(MyStruct())
 
-// CHECK: sil_witness_table MyStruct: Proto module TestModule{{$}}
+// CHECK-NOT: sil_witness_table MyStruct: Proto module TestModule