[llvm] r354314 - [NFC] API for signaling that the current loop is being deleted

[Max Kazantsev via llvm-commits]

Author: mkazantsev
Date: Tue Feb 19 03:14:05 2019
New Revision: 354314

URL: http://llvm.org/viewvc/llvm-project?rev=354314&view=rev
Log:
[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.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp?rev=354314&r1=354313&r2=354314&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp Tue Feb 19 03:14:05 2019
@@ -596,6 +596,10 @@ public:
 
     return true;
   }
+
+  bool foldingBreaksCurrentLoop() const {
+    return DeleteCurrentLoop;
+  }
 };
 } // namespace
 
@@ -603,7 +607,8 @@ public:
 /// 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 @@ static bool constantFoldTerminators(Loop
     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 mergeBlocksIntoPredecessors(
 }
 
 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 @@ static bool simplifyLoopCFG(Loop &L, Dom
 
 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 @@ public:
     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 @@ public:
       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 {