[SimplifyCFG] Teach SinkCommonCodeFromPredecessors() to preserve DomTree

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 6af60467cf4546f1da95db5b93d2d925cc511939..2fcfc557393a9ce6df3d562a8d0d00cfe9c14270 100644 (file)
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1812,7 +1812,8 @@ namespace {
 /// true, sink any common code from the predecessors to BB.
 /// We also allow one predecessor to end with conditional branch (but no more
 /// than one).
-static bool SinkCommonCodeFromPredecessors(BasicBlock *BB) {
+static bool SinkCommonCodeFromPredecessors(BasicBlock *BB,
+                                           DomTreeUpdater *DTU) {
   // We support two situations:
   //   (1) all incoming arcs are unconditional
   //   (2) one incoming arc is conditional
@@ -1930,7 +1931,8 @@ static bool SinkCommonCodeFromPredecessors(BasicBlock *BB) {
     LLVM_DEBUG(dbgs() << "SINK: Splitting edge\n");
     // We have a conditional edge and we're going to sink some instructions.
     // Insert a new block postdominating all blocks we're going to sink from.
-    if (!SplitBlockPredecessors(BB, UnconditionalPreds, ".sink.split"))
+    if (!SplitBlockPredecessors(BB, UnconditionalPreds, ".sink.split",
+                                DTU ? &DTU->getDomTree() : nullptr))
       // Edges couldn't be split.
       return false;
     Changed = true;
@@ -6461,7 +6463,7 @@ bool SimplifyCFGOpt::simplifyOnceImpl(BasicBlock *BB) {
     return true;
 
   if (SinkCommon && Options.SinkCommonInsts)
-    Changed |= SinkCommonCodeFromPredecessors(BB);
+    Changed |= SinkCommonCodeFromPredecessors(BB, DTU);
 
   IRBuilder<> Builder(BB);
 

diff --git a/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll b/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
index 00329ae5d640f1fb4ec1ad45d3805c8b578eb388..48dd2d92f4c3a4a503e7cd736d2d06febee03623 100644 (file)
--- a/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
+++ b/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -simplifycfg -sink-common-insts -S | FileCheck -enable-var-scope %s
+; RUN: opt < %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -sink-common-insts -S | FileCheck -enable-var-scope %s
 ; RUN: opt < %s -passes='simplify-cfg<sink-common-insts>' -S | FileCheck -enable-var-scope %s
 
 define zeroext i1 @test1(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32 %nblks) {