[llvm] 0bc9834 - [LICM] Use DomTreeUpdater version of SplitBlockPredecessors, nfc (#107190)

[via llvm-commits]

Author: Joshua Cao
Date: 2024-09-29T21:28:45-07:00
New Revision: 0bc98349c84130babb6a4acf2951a0ccc84f574f

URL: https://github.com/llvm/llvm-project/commit/0bc98349c84130babb6a4acf2951a0ccc84f574f
DIFF: https://github.com/llvm/llvm-project/commit/0bc98349c84130babb6a4acf2951a0ccc84f574f.diff

LOG: [LICM] Use DomTreeUpdater version of SplitBlockPredecessors, nfc (#107190)

The DominatorTree version is marked for deprecation, so we use the
DomTreeUpdater version. We also update sinkRegion() to iterate over
basic blocks instead of DomTreeNodes. The loop body calls
SplitBlockPredecessors. The DTU version calls
DomTreeUpdater::apply_updates(), which may call DominatorTree::reset().
This invalidates the worklist of DomTreeNodes to iterate over.

Added: 
    

Modified: 
    llvm/include/llvm/Transforms/Utils/LoopUtils.h
    llvm/lib/Transforms/Scalar/LICM.cpp
    llvm/lib/Transforms/Utils/LoopUtils.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Transforms/Utils/LoopUtils.h b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
index a761859465210b..4b3d6fbed8362e 100644
--- a/llvm/include/llvm/Transforms/Utils/LoopUtils.h
+++ b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
@@ -224,9 +224,9 @@ bool promoteLoopAccessesToScalars(
     bool AllowSpeculation, bool HasReadsOutsideSet);
 
 /// Does a BFS from a given node to all of its children inside a given loop.
-/// The returned vector of nodes includes the starting point.
-SmallVector<DomTreeNode *, 16> collectChildrenInLoop(DomTreeNode *N,
-                                                     const Loop *CurLoop);
+/// The returned vector of basic blocks includes the starting point.
+SmallVector<BasicBlock *, 16>
+collectChildrenInLoop(DominatorTree *DT, DomTreeNode *N, const Loop *CurLoop);
 
 /// Returns the instructions that use values defined in the loop.
 SmallVector<Instruction *, 8> findDefsUsedOutsideOfLoop(Loop *L);

diff  --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 4b1650b93cc1d1..d73b550741fb39 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -44,6 +44,7 @@
 #include "llvm/Analysis/AliasSetTracker.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Analysis/DomTreeUpdater.h"
 #include "llvm/Analysis/GuardUtils.h"
 #include "llvm/Analysis/LazyBlockFrequencyInfo.h"
 #include "llvm/Analysis/Loads.h"
@@ -65,9 +66,9 @@
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Dominators.h"
+#include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
-#include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/PatternMatch.h"
@@ -567,12 +568,11 @@ bool llvm::sinkRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI,
   // We want to visit children before parents. We will enqueue all the parents
   // before their children in the worklist and process the worklist in reverse
   // order.
-  SmallVector<DomTreeNode *, 16> Worklist = collectChildrenInLoop(N, CurLoop);
+  SmallVector<BasicBlock *, 16> Worklist =
+      collectChildrenInLoop(DT, N, CurLoop);
 
   bool Changed = false;
-  for (DomTreeNode *DTN : reverse(Worklist)) {
-    BasicBlock *BB = DTN->getBlock();
-    // Only need to process the contents of this block if it is not part of a
+  for (BasicBlock *BB : reverse(Worklist)) {
     // subloop (which would already have been processed).
     if (inSubLoop(BB, CurLoop, LI))
       continue;
@@ -1603,13 +1603,14 @@ static void splitPredecessorsOfLoopExit(PHINode *PN, DominatorTree *DT,
   //
   const auto &BlockColors = SafetyInfo->getBlockColors();
   SmallSetVector<BasicBlock *, 8> PredBBs(pred_begin(ExitBB), pred_end(ExitBB));
+  DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Lazy);
   while (!PredBBs.empty()) {
     BasicBlock *PredBB = *PredBBs.begin();
     assert(CurLoop->contains(PredBB) &&
            "Expect all predecessors are in the loop");
     if (PN->getBasicBlockIndex(PredBB) >= 0) {
       BasicBlock *NewPred = SplitBlockPredecessors(
-          ExitBB, PredBB, ".split.loop.exit", DT, LI, MSSAU, true);
+          ExitBB, PredBB, ".split.loop.exit", &DTU, LI, MSSAU, true);
       // Since we do not allow splitting EH-block with BlockColors in
       // canSplitPredecessors(), we can simply assign predecessor's color to
       // the new block.

diff  --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 9a4289e1a30da0..70047273c3b9af 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -445,21 +445,22 @@ TransformationMode llvm::hasLICMVersioningTransformation(const Loop *L) {
 }
 
 /// Does a BFS from a given node to all of its children inside a given loop.
-/// The returned vector of nodes includes the starting point.
-SmallVector<DomTreeNode *, 16>
-llvm::collectChildrenInLoop(DomTreeNode *N, const Loop *CurLoop) {
-  SmallVector<DomTreeNode *, 16> Worklist;
+/// The returned vector of basic blocks includes the starting point.
+SmallVector<BasicBlock *, 16> llvm::collectChildrenInLoop(DominatorTree *DT,
+                                                          DomTreeNode *N,
+                                                          const Loop *CurLoop) {
+  SmallVector<BasicBlock *, 16> Worklist;
   auto AddRegionToWorklist = [&](DomTreeNode *DTN) {
     // Only include subregions in the top level loop.
     BasicBlock *BB = DTN->getBlock();
     if (CurLoop->contains(BB))
-      Worklist.push_back(DTN);
+      Worklist.push_back(DTN->getBlock());
   };
 
   AddRegionToWorklist(N);
 
   for (size_t I = 0; I < Worklist.size(); I++) {
-    for (DomTreeNode *Child : Worklist[I]->children())
+    for (DomTreeNode *Child : DT->getNode(Worklist[I])->children())
       AddRegionToWorklist(Child);
   }