Merge pull request swiftlang#35935 from eeckstein/basicblock-worklist

SIL: A utility for processing basic blocks in a worklist.

Author: eeckstein

include/swift/SIL/SILBitfield.h renamed to include/swift/SIL/BasicBlockBits.h

@@ -1,4 +1,4 @@
-//===--- SILBitField.h - Defines the bitfield utilities ---------*- C++ -*-===//
+//===--- BasicBlockBits.h - SILBasicBlock bit utilities ---------*- C++ -*-===//
 //
 // This source file is part of the Swift.org open source project
 //
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file defines the BasicBlockBitfield and BasicBlockFlag utilities.
+// This file defines utilities for BasicBlock bit fields and sets.
 //
 //===----------------------------------------------------------------------===//
 
@@ -211,6 +211,63 @@ template <unsigned N> class BasicBlockSetVector {
   }
 };
 
+/// A utility for processing basic blocks in a worklist.
+///
+/// It is basically a combination of a block vector and a block set. It can be
+/// used for typical worklist-processing algorithms.
+template <unsigned N> class BasicBlockWorklist {
+  llvm::SmallVector<SILBasicBlock *, N> worklist;
+  BasicBlockSet visited;
+  
+public:
+  /// Construct an empty worklist.
+  BasicBlockWorklist(SILFunction *function) : visited(function) {}
+
+  /// Initialize the worklist with \p initialBlock.
+  BasicBlockWorklist(SILBasicBlock *initialBlock)
+      : visited(initialBlock->getParent()) {
+    push(initialBlock);
+  }
+
+  /// Pops the last added element from the worklist or returns null, if the
+  /// worklist is empty.
+  SILBasicBlock *pop() {
+    if (worklist.empty())
+      return nullptr;
+    return worklist.pop_back_val();
+  }
+
+  /// Pushes \p block onto the worklist if \p block has never been push before.
+  bool pushIfNotVisited(SILBasicBlock *block) {
+    if (visited.insert(block)) {
+      worklist.push_back(block);
+      return true;
+    }
+    return false;
+  }
+
+  /// Like `pushIfNotVisited`, but requires that \p block has never been on the
+  /// worklist before.
+  void push(SILBasicBlock *block) {
+    assert(!visited.contains(block));
+    visited.insert(block);
+    worklist.push_back(block);
+  }
+
+  /// Like `pop`, but marks the returned block as "unvisited". This means, that
+  /// the block can be pushed onto the worklist again.
+  SILBasicBlock *popAndForget() {
+    if (worklist.empty())
+      return nullptr;
+    SILBasicBlock *block = worklist.pop_back_val();
+    visited.erase(block);
+    return block;
+  }
+
+  /// Returns true if \p block was visited, i.e. has been added to the worklist.
+  bool isVisited(SILBasicBlock *block) const { return visited.contains(block); }
+};
+
 } // namespace swift
 
 #endif

include/swift/SIL/BasicBlockUtils.h

@@ -14,7 +14,7 @@
 #define SWIFT_SIL_BASICBLOCKUTILS_H
 
 #include "swift/SIL/SILValue.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"

include/swift/SIL/LinearLifetimeChecker.h

@@ -21,7 +21,7 @@
 #include "swift/SIL/SILFunction.h"
 #include "swift/SIL/SILValue.h"
 #include "swift/SIL/BasicBlockUtils.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "llvm/ADT/SmallPtrSet.h"
 
 namespace swift {

include/swift/SILOptimizer/Utils/BasicBlockOptUtils.h

@@ -23,7 +23,7 @@
 #define SWIFT_SILOPTIMIZER_UTILS_BASICBLOCKOPTUTILS_H
 
 #include "swift/SIL/SILBasicBlock.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "swift/SIL/SILCloner.h"
 #include "swift/SIL/SILInstruction.h"
 #include "swift/SILOptimizer/Utils/InstOptUtils.h"

include/swift/SILOptimizer/Utils/ValueLifetime.h

@@ -20,7 +20,7 @@
 #include "swift/Basic/STLExtras.h"
 #include "swift/SIL/SILBuilder.h"
 #include "swift/SIL/SILInstruction.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "swift/SILOptimizer/Utils/InstOptUtils.h"
 
 namespace swift {

lib/IRGen/IRGenSIL.cpp

@@ -32,7 +32,7 @@
 #include "swift/SIL/InstructionUtils.h"
 #include "swift/SIL/MemAccessUtils.h"
 #include "swift/SIL/PrettyStackTrace.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "swift/SIL/SILDebugScope.h"
 #include "swift/SIL/SILDeclRef.h"
 #include "swift/SIL/SILLinkage.h"
@@ -2017,16 +2017,10 @@ void IRGenSILFunction::emitSILFunction() {
 
   // Invariant: for every block in the work queue, we have visited all
   // of its dominators.
-  BasicBlockSet visitedBlocks(CurSILFn);
-  SmallVector<SILBasicBlock*, 8> workQueue; // really a stack
-
-  // Queue up the entry block, for which the invariant trivially holds.
-  visitedBlocks.insert(&*CurSILFn->begin());
-  workQueue.push_back(&*CurSILFn->begin());
-
-  while (!workQueue.empty()) {
-    auto bb = workQueue.pop_back_val();
+  // Start with the entry block, for which the invariant trivially holds.
+  BasicBlockWorklist<32> workQueue(&*CurSILFn->getEntryBlock());
 
+  while (SILBasicBlock *bb = workQueue.pop()) {
     // Emit the block.
     visitSILBasicBlock(bb);
 
@@ -2052,15 +2046,14 @@ void IRGenSILFunction::emitSILFunction() {
     // Therefore the invariant holds of all the successors, and we can
     // queue them up if we haven't already visited them.
     for (auto *succBB : bb->getSuccessorBlocks()) {
-      if (visitedBlocks.insert(succBB))
-        workQueue.push_back(succBB);
+      workQueue.pushIfNotVisited(succBB);
     }
   }
 
   // If there are dead blocks in the SIL function, we might have left
   // invalid blocks in the IR.  Do another pass and kill them off.
   for (SILBasicBlock &bb : *CurSILFn)
-    if (!visitedBlocks.contains(&bb))
+    if (!workQueue.isVisited(&bb))
       LoweredBBs[&bb].bb->eraseFromParent();
 
 }

lib/SIL/Verifier/SILVerifier.cpp

@@ -33,7 +33,7 @@
 #include "swift/SIL/OwnershipUtils.h"
 #include "swift/SIL/PostOrder.h"
 #include "swift/SIL/PrettyStackTrace.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "swift/SIL/SILDebugScope.h"
 #include "swift/SIL/SILFunction.h"
 #include "swift/SIL/SILModule.h"

lib/SILOptimizer/LoopTransforms/ArrayPropertyOpt.cpp

@@ -62,7 +62,7 @@
 #include "swift/SIL/InstructionUtils.h"
 #include "swift/SIL/Projection.h"
 #include "swift/SIL/LoopInfo.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "swift/SIL/SILCloner.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/Support/CommandLine.h"

lib/SILOptimizer/LoopTransforms/COWArrayOpt.cpp

@@ -25,7 +25,7 @@
 #include "swift/SIL/SILArgument.h"
 #include "swift/SIL/SILBuilder.h"
 #include "swift/SIL/SILInstruction.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "swift/SILOptimizer/Analysis/ARCAnalysis.h"
 #include "swift/SILOptimizer/Analysis/AliasAnalysis.h"
 #include "swift/SILOptimizer/Analysis/ArraySemantic.h"

lib/SILOptimizer/LoopTransforms/LICM.cpp

@@ -19,7 +19,7 @@
 #include "swift/SIL/SILArgument.h"
 #include "swift/SIL/SILBuilder.h"
 #include "swift/SIL/SILInstruction.h"
-#include "swift/SIL/SILBitfield.h"
+#include "swift/SIL/BasicBlockBits.h"
 #include "swift/SILOptimizer/Analysis/AccessedStorageAnalysis.h"
 #include "swift/SILOptimizer/Analysis/AliasAnalysis.h"
 #include "swift/SILOptimizer/Analysis/Analysis.h"