[SimplifyCFG] Teach mergeConditionalStoreToAddress() to preserve DomTree

lib/Transforms/Utils/SimplifyCFG.cpp

@@ -3238,12 +3238,10 @@ static Value *ensureValueAvailableInSuccessor(Value *V, BasicBlock *BB,
   return PHI;
 }
 
-static bool mergeConditionalStoreToAddress(BasicBlock *PTB, BasicBlock *PFB,
-                                           BasicBlock *QTB, BasicBlock *QFB,
-                                           BasicBlock *PostBB, Value *Address,
-                                           bool InvertPCond, bool InvertQCond,
-                                           const DataLayout &DL,
-                                           const TargetTransformInfo &TTI) {
+static bool mergeConditionalStoreToAddress(
+    BasicBlock *PTB, BasicBlock *PFB, BasicBlock *QTB, BasicBlock *QFB,
+    BasicBlock *PostBB, Value *Address, bool InvertPCond, bool InvertQCond,
+    DomTreeUpdater *DTU, const DataLayout &DL, const TargetTransformInfo &TTI) {
   // For every pointer, there must be exactly two stores, one coming from
   // PTB or PFB, and the other from QTB or QFB. We don't support more than one
   // store (to any address) in PTB,PFB or QTB,QFB.
@@ -3332,8 +3330,9 @@ static bool mergeConditionalStoreToAddress(BasicBlock *PTB, BasicBlock *PFB,
     // If QTB does not exist, then QFB's only predecessor has a conditional
     // branch to QFB and PostBB.
     BasicBlock *TruePred = QTB ? QTB : QFB->getSinglePredecessor();
-    BasicBlock *NewBB = SplitBlockPredecessors(PostBB, { QFB, TruePred},
-                                               "condstore.split");
+    BasicBlock *NewBB =
+        SplitBlockPredecessors(PostBB, {QFB, TruePred}, "condstore.split",
+                               DTU ? &DTU->getDomTree() : nullptr);
     if (!NewBB)
       return false;
     PostBB = NewBB;
@@ -3362,8 +3361,9 @@ static bool mergeConditionalStoreToAddress(BasicBlock *PTB, BasicBlock *PFB,
     QPred = QB.CreateNot(QPred);
   Value *CombinedPred = QB.CreateOr(PPred, QPred);
 
-  auto *T =
-      SplitBlockAndInsertIfThen(CombinedPred, &*QB.GetInsertPoint(), false);
+  auto *T = SplitBlockAndInsertIfThen(
+      CombinedPred, &*QB.GetInsertPoint(), /*Unreachable=*/false,
+      /*BranchWeights=*/nullptr, DTU ? &DTU->getDomTree() : nullptr);
   QB.SetInsertPoint(T);
   StoreInst *SI = cast<StoreInst>(QB.CreateStore(QPHI, Address));
   AAMDNodes AAMD;
@@ -3383,7 +3383,7 @@ static bool mergeConditionalStoreToAddress(BasicBlock *PTB, BasicBlock *PFB,
 }
 
 static bool mergeConditionalStores(BranchInst *PBI, BranchInst *QBI,
-                                   const DataLayout &DL,
+                                   DomTreeUpdater *DTU, const DataLayout &DL,
                                    const TargetTransformInfo &TTI) {
   // The intention here is to find diamonds or triangles (see below) where each
   // conditional block contains a store to the same address. Both of these
@@ -3485,12 +3485,12 @@ static bool mergeConditionalStores(BranchInst *PBI, BranchInst *QBI,
 
   bool Changed = false;
   for (auto *Address : CommonAddresses)
-    Changed |= mergeConditionalStoreToAddress(
-        PTB, PFB, QTB, QFB, PostBB, Address, InvertPCond, InvertQCond, DL, TTI);
+    Changed |=
+        mergeConditionalStoreToAddress(PTB, PFB, QTB, QFB, PostBB, Address,
+                                       InvertPCond, InvertQCond, DTU, DL, TTI);
   return Changed;
 }
 
-
 /// If the previous block ended with a widenable branch, determine if reusing
 /// the target block is profitable and legal.  This will have the effect of
 /// "widening" PBI, but doesn't require us to reason about hosting safety.
@@ -3536,6 +3536,7 @@ static bool tryWidenCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
 /// that PBI and BI are both conditional branches, and BI is in one of the
 /// successor blocks of PBI - PBI branches to BI.
 static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI,
+                                           DomTreeUpdater *DTU,
                                            const DataLayout &DL,
                                            const TargetTransformInfo &TTI) {
   assert(PBI->isConditional() && BI->isConditional());
@@ -3599,7 +3600,7 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI,
   // If both branches are conditional and both contain stores to the same
   // address, remove the stores from the conditionals and create a conditional
   // merged store at the end.
-  if (MergeCondStores && mergeConditionalStores(PBI, BI, DL, TTI))
+  if (MergeCondStores && mergeConditionalStores(PBI, BI, DTU, DL, TTI))
     return true;
 
   // If this is a conditional branch in an empty block, and if any
@@ -6347,7 +6348,7 @@ bool SimplifyCFGOpt::simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
   for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
     if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
       if (PBI != BI && PBI->isConditional())
-        if (SimplifyCondBranchToCondBranch(PBI, BI, DL, TTI))
+        if (SimplifyCondBranchToCondBranch(PBI, BI, DTU, DL, TTI))
           return requestResimplify();
 
   // Look for diamond patterns.
@@ -6355,7 +6356,7 @@ bool SimplifyCFGOpt::simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
     if (BasicBlock *PrevBB = allPredecessorsComeFromSameSource(BB))
       if (BranchInst *PBI = dyn_cast<BranchInst>(PrevBB->getTerminator()))
         if (PBI != BI && PBI->isConditional())
-          if (mergeConditionalStores(PBI, BI, DL, TTI))
+          if (mergeConditionalStores(PBI, BI, DTU, DL, TTI))
             return requestResimplify();
 
   return false;

test/Transforms/SimplifyCFG/merge-cond-stores-2.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -S < %s -simplifycfg -simplifycfg-merge-cond-stores=true -simplifycfg-merge-cond-stores-aggressively=false -phi-node-folding-threshold=1 | FileCheck %s
+; RUN: opt -S < %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -simplifycfg-merge-cond-stores=true -simplifycfg-merge-cond-stores-aggressively=false -phi-node-folding-threshold=1 | FileCheck %s
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
 target triple = "armv7--linux-gnueabihf"

test/Transforms/SimplifyCFG/merge-cond-stores.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -simplifycfg -instcombine < %s -simplifycfg-merge-cond-stores=true -simplifycfg-merge-cond-stores-aggressively=false -phi-node-folding-threshold=2 -S | FileCheck %s
+; RUN: opt -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -instcombine < %s -simplifycfg-merge-cond-stores=true -simplifycfg-merge-cond-stores-aggressively=false -phi-node-folding-threshold=2 -S | FileCheck %s
 
 ; This test should succeed and end up if-converted.
 define void @test_simple(i32* %p, i32 %a, i32 %b) {

test/Transforms/SimplifyCFG/preserve-store-alignment.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -simplifycfg -S < %s | FileCheck %s
+; RUN: opt -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S < %s | FileCheck %s
 
 %struct.Counters = type { i64, i64, i64, [8 x i8] }