commit 58b987211a031ee54a57ce972e81ab8525b2148f
author Max Kazantsev <max.kazantsev@azul.com> Tue Feb 19 11:14:05 2019 +0000
committer Max Kazantsev <max.kazantsev@azul.com> Tue Feb 19 11:14:05 2019 +0000
tree de6ce59993a2917490fb11f2ce65bc996c5f342c
parent 394aa566582c66f2f31bb4bed521206c7b18be59

[NFC] API for signaling that the current loop is being deleted

We are planning to be able to delete the current loop in LoopSimplifyCFG
in the future. Add API to notify the loop pass manager that it happened.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354314 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/LoopSimplifyCFG.cpp

diff --git a/lib/Transforms/Scalar/LoopSimplifyCFG.cpp b/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
index fd41705..55cf20a 100644
--- a/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+++ b/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -596,6 +596,10 @@
 
     return true;
   }
+
+  bool foldingBreaksCurrentLoop() const {
+    return DeleteCurrentLoop;
+  }
 };
 } // namespace
 
@@ -603,7 +607,8 @@
 /// branches.
 static bool constantFoldTerminators(Loop &L, DominatorTree &DT, LoopInfo &LI,
                                     ScalarEvolution &SE,
-                                    MemorySSAUpdater *MSSAU) {
+                                    MemorySSAUpdater *MSSAU,
+                                    bool &IsLoopDeleted) {
   if (!EnableTermFolding)
     return false;
 
@@ -613,7 +618,9 @@
     return false;
 
   ConstantTerminatorFoldingImpl BranchFolder(L, LI, DT, SE, MSSAU);
-  return BranchFolder.run();
+  bool Changed = BranchFolder.run();
+  IsLoopDeleted = Changed && BranchFolder.foldingBreaksCurrentLoop();
+  return Changed;
 }
 
 static bool mergeBlocksIntoPredecessors(Loop &L, DominatorTree &DT,
@@ -645,11 +652,15 @@
 }
 
 static bool simplifyLoopCFG(Loop &L, DominatorTree &DT, LoopInfo &LI,
-                            ScalarEvolution &SE, MemorySSAUpdater *MSSAU) {
+                            ScalarEvolution &SE, MemorySSAUpdater *MSSAU,
+                            bool &isLoopDeleted) {
   bool Changed = false;
 
   // Constant-fold terminators with known constant conditions.
-  Changed |= constantFoldTerminators(L, DT, LI, SE, MSSAU);
+  Changed |= constantFoldTerminators(L, DT, LI, SE, MSSAU, isLoopDeleted);
+
+  if (isLoopDeleted)
+    return true;
 
   // Eliminate unconditional branches by merging blocks into their predecessors.
   Changed |= mergeBlocksIntoPredecessors(L, DT, LI, MSSAU);
@@ -662,14 +673,19 @@
 
 PreservedAnalyses LoopSimplifyCFGPass::run(Loop &L, LoopAnalysisManager &AM,
                                            LoopStandardAnalysisResults &AR,
-                                           LPMUpdater &) {
+                                           LPMUpdater &LPMU) {
   Optional<MemorySSAUpdater> MSSAU;
   if (EnableMSSALoopDependency && AR.MSSA)
     MSSAU = MemorySSAUpdater(AR.MSSA);
+  bool DeleteCurrentLoop = false;
   if (!simplifyLoopCFG(L, AR.DT, AR.LI, AR.SE,
-                       MSSAU.hasValue() ? MSSAU.getPointer() : nullptr))
+                       MSSAU.hasValue() ? MSSAU.getPointer() : nullptr,
+                       DeleteCurrentLoop))
     return PreservedAnalyses::all();
 
+  if (DeleteCurrentLoop)
+    LPMU.markLoopAsDeleted(L, "loop-simplifycfg");
+
   return getLoopPassPreservedAnalyses();
 }
 
@@ -681,7 +697,7 @@
     initializeLoopSimplifyCFGLegacyPassPass(*PassRegistry::getPassRegistry());
   }
 
-  bool runOnLoop(Loop *L, LPPassManager &) override {
+  bool runOnLoop(Loop *L, LPPassManager &LPM) override {
     if (skipLoop(L))
       return false;
 
@@ -695,8 +711,13 @@
       if (VerifyMemorySSA)
         MSSA->verifyMemorySSA();
     }
-    return simplifyLoopCFG(*L, DT, LI, SE,
-                           MSSAU.hasValue() ? MSSAU.getPointer() : nullptr);
+    bool DeleteCurrentLoop = false;
+    bool Changed = simplifyLoopCFG(
+        *L, DT, LI, SE, MSSAU.hasValue() ? MSSAU.getPointer() : nullptr,
+        DeleteCurrentLoop);
+    if (DeleteCurrentLoop)
+      LPM.markLoopAsDeleted(*L);
+    return Changed;
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {