[PATCH] D74691: [Attributor] add some pattern to containsCycle

[omar ahmed via Phabricator via llvm-commits]

omarahmed updated this revision to Diff 245166.
omarahmed added a comment.

- change containsCycle impl approach


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D74691/new/

https://reviews.llvm.org/D74691

Files:
  llvm/lib/Transforms/IPO/Attributor.cpp


Index: llvm/lib/Transforms/IPO/Attributor.cpp
===================================================================
--- llvm/lib/Transforms/IPO/Attributor.cpp
+++ llvm/lib/Transforms/IPO/Attributor.cpp
@@ -2368,14 +2368,22 @@
 
 // Helper function that checks whether a function has any cycle.
 // TODO: Replace with more efficent code
-static bool containsCycle(Function &F) {
-  SmallPtrSet<BasicBlock *, 32> Visited;
-
-  // Traverse BB by dfs and check whether successor is already visited.
-  for (BasicBlock *BB : depth_first(&F)) {
-    Visited.insert(BB);
-    for (auto *SuccBB : successors(BB)) {
-      if (Visited.count(SuccBB))
+static bool containsCycle(Function &F,Attributor &A) {
+  for (scc_iterator<Function *> I = scc_begin(&F), IE = scc_end(&F); I != IE;
+       ++I) {
+    const std::vector<BasicBlock *> &SCCBBs = *I;
+    ScalarEvolution *SE =
+        A.getInfoCache().getAnalysisResultForFunction<ScalarEvolutionAnalysis>(
+            F);
+    LoopInfo *LI =
+        A.getInfoCache().getAnalysisResultForFunction<LoopAnalysis>(F);
+    if (!LI || !SE) continue;
+    std::vector<BasicBlock *>::const_iterator BBI = SCCBBs.begin();
+    Loop *L = LI->getLoopFor(*BBI);
+    L = L->getParentLoop();
+    if (L) {
+      if (L->getNumBlocks() == SCCBBs.size() &&
+          !SE->getSmallConstantMaxTripCount(L))
         return true;
     }
   }
@@ -2386,8 +2394,8 @@
 // endless loop
 // FIXME: Any cycle is regarded as endless loop for now.
 //        We have to allow some patterns.
-static bool containsPossiblyEndlessLoop(Function *F) {
-  return !F || !F->hasExactDefinition() || containsCycle(*F);
+static bool containsPossiblyEndlessLoop(Function *F,Attributor &A) {  
+  return !F || !F->hasExactDefinition() || containsCycle(*F,A);
 }
 
 struct AAWillReturnImpl : public AAWillReturn {
@@ -2398,7 +2406,7 @@
     AAWillReturn::initialize(A);
 
     Function *F = getAssociatedFunction();
-    if (containsPossiblyEndlessLoop(F))
+    if (containsPossiblyEndlessLoop(F,A))
       indicatePessimisticFixpoint();
   }
 
@@ -7374,7 +7382,7 @@
     for (Instruction *I : OpcodeInstMap[Opcode]) {
       // Skip dead instructions.
       if (A && A->isAssumedDead(IRPosition::value(*I), QueryingAA, LivenessAA,
-                                CheckBBLivenessOnly))
+				 CheckBBLivenessOnly))
         continue;
 
       if (!Pred(*I))


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