Merge remote-tracking branch 'origin/master' into master-next

Author: swift-ci

lib/SILOptimizer/Transforms/SimplifyCFG.cpp

@@ -192,6 +192,7 @@ namespace {
     bool simplifyArgument(SILBasicBlock *BB, unsigned i);
     bool simplifyArgs(SILBasicBlock *BB);
     void findLoopHeaders();
+    bool simplifySwitchEnumOnObjcClassOptional(SwitchEnumInst *SEI);
   };
 
 } // end anonymous namespace
@@ -1731,6 +1732,212 @@ bool SimplifyCFG::simplifySwitchEnumUnreachableBlocks(SwitchEnumInst *SEI) {
   return true;
 }
 
+/// Checks that the someBB only contains obj_method calls (possibly chained) on
+/// the optional value.
+///
+/// switch_enum %optionalValue, case #Optional.some!enumelt.1: someBB
+///
+/// someBB(%optionalPayload):
+///    %1 = objc_method %optionalPayload
+///    %2 = apply %1(..., %optionalPayload) // self position
+///    %3 = unchecked_ref_cast %2
+///    %4 = objc_method %3
+///    %... = apply %4(..., %3)
+///    br mergeBB(%...)
+static bool containsOnlyObjMethodCallOnOptional(SILValue optionalValue,
+                                                SILBasicBlock *someBB,
+                                                SILValue &outBranchArg,
+                                                SILValue &outOptionalPayload) {
+  SILValue optionalPayload;
+  SmallVector<SILValue, 4> optionalPayloads;
+  if (someBB->getNumArguments() == 1) {
+    optionalPayload = someBB->getArgument(0);
+    optionalPayloads.push_back(optionalPayload);
+  } else if (someBB->getNumArguments() != 0)
+    return false;
+
+  SmallVector<SILValue, 4> objCApplies;
+  for (auto &i : *someBB) {
+    SILInstruction *inst = &i;
+    if (onlyAffectsRefCount(inst))
+      continue;
+    if (inst->isDebugInstruction())
+      continue;
+    // An objc_method has no sideffects.
+    if (isa<ObjCMethodInst>(inst))
+      continue;
+
+    // An uncheckedEnumData has no sideeffects.
+    if (auto *uncheckedEnumData = dyn_cast<UncheckedEnumDataInst>(inst)) {
+      if (uncheckedEnumData->getOperand() != optionalValue)
+        continue;
+      optionalPayload = uncheckedEnumData;
+      optionalPayloads.push_back(uncheckedEnumData);
+      continue;
+    }
+
+    // An unchecked_ref_cast is safe.
+    if (auto *refCast = dyn_cast<UncheckedRefCastInst>(inst)) {
+      // An unchecked_ref_cast on a safe objc_method apply behaves like the
+      // optional (it is null if the optional was null).
+      if (refCast->getType().getClassOrBoundGenericClass() &&
+          std::find(objCApplies.begin(), objCApplies.end(),
+                    refCast->getOperand()) != objCApplies.end())
+        optionalPayloads.push_back(refCast);
+      continue;
+    }
+
+    // Applies on objc_methods where self is either the optional payload or the
+    // result of another 'safe' apply are safe.
+    if (auto *objcMethod = dyn_cast<ApplyInst>(inst)) {
+      if (!isa<ObjCMethodInst>(objcMethod->getCallee()))
+        return false;
+      if (std::find(optionalPayloads.begin(), optionalPayloads.end(),
+                    objcMethod->getSelfArgument()) == optionalPayloads.end())
+        return false;
+      objCApplies.push_back(objcMethod);
+      continue;
+    }
+
+    // The branch should forward one of the objc_method call.
+    if (auto *br = dyn_cast<BranchInst>(inst)) {
+      if (br->getNumArgs() == 0 || br->getNumArgs() > 1)
+        return false;
+      auto branchArg = br->getArg(0);
+      if (std::find(objCApplies.begin(), objCApplies.end(), branchArg) ==
+          objCApplies.end())
+        return false;
+      outBranchArg = branchArg;
+      continue;
+    }
+    // Unexpected instruction.
+    return false;
+  }
+  if (!optionalPayload)
+    return false;
+  outOptionalPayload = optionalPayload;
+  return true;
+}
+
+/// Check that all that noneBB does is forwarding none.
+/// The only other allowed operation are ref count operations.
+static bool onlyForwardsNone(SILBasicBlock *noneBB, SILBasicBlock *someBB,
+                             SwitchEnumInst *SEI) {
+  // It all the basic blocks leading up to the ultimate block we only expect
+  // reference count instructions.
+  while (noneBB->getSingleSuccessorBlock() != someBB->getSingleSuccessorBlock()) {
+    for (auto &i : *noneBB) {
+      auto *inst = &i;
+      if (isa<BranchInst>(inst) || onlyAffectsRefCount(inst) ||
+          inst->isDebugInstruction())
+        continue;
+      return false;
+    }
+    noneBB = noneBB->getSingleSuccessorBlock();
+  }
+  // The ultimate block forwards the Optional<...>.none value.
+  SILValue optionalNone;
+  for (auto &i : *noneBB) {
+    auto *inst = &i;
+    if (onlyAffectsRefCount(inst) || inst->isDebugInstruction())
+      continue;
+    if (auto *none = dyn_cast<EnumInst>(inst)) {
+      if (none->getElement() !=
+          SEI->getModule().getASTContext().getOptionalNoneDecl())
+        return false;
+      optionalNone = none;
+      continue;
+    }
+    if (auto *noneBranch = dyn_cast<BranchInst>(inst)) {
+      if (noneBranch->getNumArgs() != 1 ||
+          (noneBranch->getArg(0) != SEI->getOperand() &&
+           noneBranch->getArg(0) != optionalNone))
+        return false;
+      continue;
+    }
+    return false;
+  }
+  return true;
+}
+
+/// Check whether \p noneBB has the same ultimate successor as the successor to someBB.
+///  someBB       noneBB
+///   \             |
+///    \            ... (more bbs?)
+///     \           /
+///       ulimateBB
+static bool hasSameUlitmateSuccessor(SILBasicBlock *noneBB, SILBasicBlock *someBB) {
+  auto *someSuccessorBB = someBB->getSingleSuccessorBlock();
+  if (!someSuccessorBB)
+    return false;
+  auto *noneSuccessorBB = noneBB->getSingleSuccessorBlock();
+  while (noneSuccessorBB != nullptr && noneSuccessorBB != someSuccessorBB)
+    noneSuccessorBB = noneSuccessorBB->getSingleSuccessorBlock();
+  return noneSuccessorBB == someSuccessorBB;
+}
+
+/// Simplify switch_enums on class enums that branch to objc_method calls on
+/// that optional on the #Optional.some side to always branch to the some side.
+///
+/// switch_enum %optionalValue, case #Optional.some!enumelt.1: someBB,
+///                             case #Optional.none: noneBB
+///
+/// someBB(%optionalPayload):
+///    %1 = objc_method %optionalPayload
+///    %2 = apply %1(..., %optionalPayload) // self position
+///    br mergeBB(%2)
+///
+/// noneBB:
+///    %4 = enum #Optional.none
+///    br mergeBB(%4)
+bool SimplifyCFG::simplifySwitchEnumOnObjcClassOptional(SwitchEnumInst *SEI) {
+  auto optional = SEI->getOperand();
+  auto optionalPayloadType = optional->getType().getOptionalObjectType();
+  if (!optionalPayloadType ||
+      !optionalPayloadType.getClassOrBoundGenericClass())
+    return false;
+
+  if (SEI->getNumCases() != 2)
+    return false;
+
+  auto *noneBB = SEI->getCase(0).second;
+  auto *someBB = SEI->getCase(1).second;
+  if (noneBB == someBB)
+    return false;
+  auto someDecl = SEI->getModule().getASTContext().getOptionalSomeDecl();
+  if (SEI->getCaseDestination(someDecl) != someBB)
+    std::swap(someBB, noneBB);
+
+  if (!hasSameUlitmateSuccessor(noneBB, someBB))
+    return false;
+
+  if (!onlyForwardsNone(noneBB, someBB, SEI))
+    return false;
+
+  SILValue branchArg;
+  SILValue optionalPayload;
+  if (!containsOnlyObjMethodCallOnOptional(optional, someBB, branchArg,
+                                           optionalPayload))
+    return false;
+
+  SILBuilderWithScope Builder(SEI);
+  auto *payloadCast = Builder.createUncheckedRefCast(SEI->getLoc(), optional,
+                                                     optionalPayloadType);
+  optionalPayload->replaceAllUsesWith(payloadCast);
+  auto *switchBB = SEI->getParent();
+  if (someBB->getNumArguments())
+    Builder.createBranch(SEI->getLoc(), someBB, SILValue(payloadCast));
+  else
+    Builder.createBranch(SEI->getLoc(), someBB);
+
+  SEI->eraseFromParent();
+  addToWorklist(switchBB);
+  simplifyAfterDroppingPredecessor(noneBB);
+  addToWorklist(someBB);
+  ++NumConstantFolded;
+  return true;
+}
+
 /// simplifySwitchEnumBlock - Simplify a basic block that ends with a
 /// switch_enum instruction that gets its operand from an enum
 /// instruction.
@@ -2316,7 +2523,9 @@ bool SimplifyCFG::simplifyBlocks() {
     case TermKind::SwitchEnumInst: {
       auto *SEI = cast<SwitchEnumInst>(TI);
       if (simplifySwitchEnumBlock(SEI)) {
-        Changed = false;
+        Changed = true;
+      } else if (simplifySwitchEnumOnObjcClassOptional(SEI)) {
+        Changed = true;
       } else {
         Changed |= simplifySwitchEnumUnreachableBlocks(SEI);
       }

test/SILOptimizer/Inputs/objc_optional.h

@@ -0,0 +1,5 @@
+@import Foundation;
+
+@interface Test : NSObject
+  @property (nullable) Test *otherTest;
+@end