LICM: (limited) support for OSSA

The first step: allow hoisting instructions which only have trivial operands and results.

Author: eeckstein

lib/SILOptimizer/LoopTransforms/LICM.cpp

@@ -849,6 +849,21 @@ static bool analyzeBeginAccess(BeginAccessInst *BI,
   return true;
 }
 
+static bool hasOwnershipOperandsOrResults(SILInstruction *inst) {
+  if (!inst->getFunction()->hasOwnership())
+    return false;
+
+  for (SILValue result : inst->getResults()) {
+    if (result->getOwnershipKind() != OwnershipKind::None)
+      return true;
+  }
+  for (Operand &op : inst->getAllOperands()) {
+    if (op.get()->getOwnershipKind() != OwnershipKind::None)
+      return true;
+  }
+  return false;
+}
+
 // Analyzes current loop for hosting/sinking potential:
 // Computes set of instructions we may be able to move out of the loop
 // Important Note:
@@ -887,6 +902,10 @@ void LoopTreeOptimization::analyzeCurrentLoop(
   for (auto *BB : Loop->getBlocks()) {
     SmallVector<SILInstruction *, 8> sideEffectsInBlock;
     for (auto &Inst : *BB) {
+      if (hasOwnershipOperandsOrResults(&Inst)) {
+        checkSideEffects(Inst, sideEffects, sideEffectsInBlock);
+        continue;
+      }
       switch (Inst.getKind()) {
       case SILInstructionKind::FixLifetimeInst: {
         auto *FL = cast<FixLifetimeInst>(&Inst);
@@ -1084,11 +1103,14 @@ SingleValueInstruction *LoopTreeOptimization::splitLoad(
     SILValue splitAddress, ArrayRef<AccessPath::Index> remainingPath,
     SILBuilder &builder, SmallVectorImpl<LoadInst *> &Loads, unsigned ldstIdx) {
   auto loc = LoadsAndStores[ldstIdx]->getLoc();
+  LoadOwnershipQualifier ownership = builder.getFunction().hasOwnership() ?
+      LoadOwnershipQualifier::Trivial :
+      LoadOwnershipQualifier::Unqualified;
+
   // Recurse until we have a load that matches accessPath.
   if (remainingPath.empty()) {
     // Create a load that matches the stored access path.
-    LoadInst *load = builder.createLoad(loc, splitAddress,
-                                        LoadOwnershipQualifier::Unqualified);
+    LoadInst *load = builder.createLoad(loc, splitAddress, ownership);
     Loads.push_back(load);
     // Replace the outer load in the list of loads and stores to hoist and
     // sink. LoadsAndStores must remain in instruction order.
@@ -1112,8 +1134,7 @@ SingleValueInstruction *LoopTreeOptimization::splitLoad(
         elementVal = splitLoad(projection, remainingPath.drop_back(), builder,
                                Loads, ldstIdx);
       } else {
-        elementVal = builder.createLoad(loc, projection,
-                                        LoadOwnershipQualifier::Unqualified);
+        elementVal = builder.createLoad(loc, projection, ownership);
         recordDisjointLoad(cast<LoadInst>(elementVal));
       }
       elements.push_back(elementVal);
@@ -1136,8 +1157,7 @@ SingleValueInstruction *LoopTreeOptimization::splitLoad(
       fieldVal = splitLoad(projection, remainingPath.drop_back(), builder,
                            Loads, ldstIdx);
     else {
-      fieldVal = builder.createLoad(loc, projection,
-                                    LoadOwnershipQualifier::Unqualified);
+      fieldVal = builder.createLoad(loc, projection, ownership);
       recordDisjointLoad(cast<LoadInst>(fieldVal));
     }
     elements.push_back(fieldVal);
@@ -1431,9 +1451,13 @@ hoistLoadsAndStores(AccessPath accessPath, SILLoop *loop) {
   if (!initialAddr)
     return;
 
+  LoadOwnershipQualifier ownership = B.getFunction().hasOwnership() ?
+      LoadOwnershipQualifier::Trivial :
+      LoadOwnershipQualifier::Unqualified;
+
   LoadInst *initialLoad =
       B.createLoad(RegularLocation::getAutoGeneratedLocation(), initialAddr,
-                   LoadOwnershipQualifier::Unqualified);
+                   ownership);
   LLVM_DEBUG(llvm::dbgs() << "Creating preload " << *initialLoad);
   ssaUpdater.addAvailableValue(preheader, initialLoad);
 
@@ -1480,9 +1504,12 @@ hoistLoadsAndStores(AccessPath accessPath, SILLoop *loop) {
       assert(succ->getSinglePredecessorBlock()
              && "should have split critical edges");
       SILBuilder B(succ->begin());
+      StoreOwnershipQualifier ownership = B.getFunction().hasOwnership() ?
+          StoreOwnershipQualifier::Trivial :
+          StoreOwnershipQualifier::Unqualified;
       auto *SI = B.createStore(
           loc.value(), ssaUpdater.getValueInMiddleOfBlock(succ), initialAddr,
-          StoreOwnershipQualifier::Unqualified);
+          ownership);
       (void)SI;
       LLVM_DEBUG(llvm::dbgs() << "Creating loop-exit store " << *SI);
     }
@@ -1529,10 +1556,6 @@ class LICM : public SILFunctionTransform {
   void run() override {
     SILFunction *F = getFunction();
 
-    // If our function has ownership, skip it.
-    if (F->hasOwnership())
-      return;
-
     SILLoopAnalysis *LA = PM->getAnalysis<SILLoopAnalysis>();
     SILLoopInfo *LoopInfo = LA->get(F);
 

test/SILOptimizer/licm.sil

@@ -14,6 +14,10 @@ class Storage {
   init()
 }
 
+struct NonCopyable : ~Copyable {
+  var x: Int
+}
+
 // globalArray
 sil_global @globalArray : $Storage
 
@@ -218,7 +222,7 @@ bb2:
   return %52 : $()
 }
 
-public protocol P : class {
+public protocol P : AnyObject {
   func foo() -> Int32
   func boo() -> Int32
 }
@@ -1527,4 +1531,78 @@ bb2:
   return %r1 : $()
 }
 
+// CHECK-LABEL: sil [ossa] @dont_hoist_non_trivial_load :
+// CHECK:       bb1:
+// CHECK-NEXT:   load [copy]
+// CHECK:       } // end sil function 'dont_hoist_non_trivial_load'
+sil [ossa] @dont_hoist_non_trivial_load : $@convention(thin) (@inout Builtin.NativeObject) -> () {
+bb0(%0 : $*Builtin.NativeObject):
+  br bb1
+bb1:
+  %2 = load [copy] %0
+  fix_lifetime %2
+  destroy_value %2
+  cond_br undef, bb2, bb3
+bb2:
+  br bb1
+bb3:
+  %r = tuple ()
+  return %r : $()
+}
+
+// CHECK-LABEL: sil [ossa] @hoist_trivial_load :
+// CHECK:         load [trivial]
+// CHECK-NEXT:  br bb1  
+// CHECK:       } // end sil function 'hoist_trivial_load'
+sil [ossa] @hoist_trivial_load : $@convention(thin) (@inout Int) -> () {
+bb0(%0 : $*Int):
+  br bb1
+bb1:
+  %2 = load [trivial] %0
+  fix_lifetime %2
+  cond_br undef, bb2, bb3
+bb2:
+  br bb1
+bb3:
+  %r = tuple ()
+  return %r : $()
+}
+
+// CHECK-LABEL: sil [ossa] @dont_hoist_load_borrow :
+// CHECK:       bb1:
+// CHECK-NEXT:    load_borrow
+// CHECK:       } // end sil function 'dont_hoist_load_borrow'
+sil [ossa] @dont_hoist_load_borrow : $@convention(thin) (@inout Builtin.NativeObject) -> () {
+bb0(%0 : $*Builtin.NativeObject):
+  br bb1
+bb1:
+  %2 = load_borrow %0
+  fix_lifetime %2
+  end_borrow %2
+  cond_br undef, bb2, bb3
+bb2:
+  br bb1
+bb3:
+  %r = tuple ()
+  return %r : $()
+}
+
+// CHECK-LABEL: sil [ossa] @dont_hoist_struct :
+// CHECK:       bb1:
+// CHECK-NEXT:    struct $NonCopyable
+// CHECK:       } // end sil function 'dont_hoist_struct'
+sil [ossa] @dont_hoist_struct : $@convention(thin) (Int) -> () {
+bb0(%0 : $Int):
+  br bb1
+bb1:
+  %2 = struct $NonCopyable (%0)
+  fix_lifetime %2
+  destroy_value %2
+  cond_br undef, bb2, bb3
+bb2:
+  br bb1
+bb3:
+  %r = tuple ()
+  return %r : $()
+}