[PATCH] D84689: [OpenMPOpt][OldPM!] Most SCC's are uninteresting, don't waste time on them

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri updated this revision to Diff 281006.
lebedev.ri added a comment.

Fix typo.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D84689/new/

https://reviews.llvm.org/D84689

Files:
  llvm/include/llvm/Transforms/IPO/OpenMPOpt.h
  llvm/lib/Transforms/IPO/OpenMPOpt.cpp


Index: llvm/lib/Transforms/IPO/OpenMPOpt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/OpenMPOpt.cpp
+++ llvm/lib/Transforms/IPO/OpenMPOpt.cpp
@@ -1342,6 +1342,10 @@
   for (LazyCallGraph::Node &N : C)
     SCC.push_back(&N.getFunction());
 
+  // FIXME: skip SCC's that don't contain calls to OpenMP functions.
+  // The problem is that those OpenMP functions are declarations,
+  // and LazyCallGraph currently does not track them.
+
   if (SCC.empty())
     return PreservedAnalyses::all();
 
@@ -1401,12 +1405,25 @@
       return false;
 
     SmallVector<Function *, 16> SCC;
-    for (CallGraphNode *CGN : CGSCC)
-      if (Function *Fn = CGN->getFunction())
-        if (!Fn->isDeclaration())
-          SCC.push_back(Fn);
+    bool InterestingSCC = !OMPInModule.getKernels().empty();
+    for (CallGraphNode *CGN : CGSCC) {
+      Function *Fn = CGN->getFunction();
+      if (!Fn || Fn->isDeclaration())
+        continue;
+      SCC.push_back(Fn);
 
-    if (SCC.empty())
+      // Do we already know that the SCC contains kernels,
+      // or that OpenMP functions are called from this SCC?
+      if (InterestingSCC)
+        continue;
+      // If not, let's check that.
+      InterestingSCC |= any_of(*CGN, [&](CallGraphNode::CallRecord Callee) {
+        return OMPInModule.isOMPReferencedFunction(
+            Callee.second->getFunction());
+      });
+    }
+
+    if (!InterestingSCC || SCC.empty())
       return false;
 
     CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
@@ -1472,9 +1489,9 @@
   // issues an error. Work around it..
   do {
 #define OMP_RTL(_Enum, _Name, ...)                                             \
-  if (M.getFunction(_Name)) {                                                  \
+  if (Function *F = M.getFunction(_Name)) {                                    \
+    OMPInModule.OMPFuncs.insert(F);                                            \
     OMPInModule = true;                                                        \
-    break;                                                                     \
   }
 #include "llvm/Frontend/OpenMP/OMPKinds.def"
   } while (false);
Index: llvm/include/llvm/Transforms/IPO/OpenMPOpt.h
===================================================================
--- llvm/include/llvm/Transforms/IPO/OpenMPOpt.h
+++ llvm/include/llvm/Transforms/IPO/OpenMPOpt.h
@@ -33,6 +33,12 @@
   bool isKnown() { return Value != OpenMP::UNKNOWN; }
   operator bool() { return Value != OpenMP::NOT_FOUND; }
 
+  /// Is this function \p F an OpenMP function that is known ot be called
+  /// in the module?
+  bool isOMPReferencedFunction(Function *F) const {
+    return OMPFuncs.contains(F);
+  }
+
   /// Return the known kernels (=GPU entry points) in the module.
   SmallPtrSetImpl<Kernel> &getKernels() { return Kernels; }
 
@@ -42,6 +48,11 @@
 private:
   enum class OpenMP { FOUND, NOT_FOUND, UNKNOWN } Value = OpenMP::UNKNOWN;
 
+  friend bool containsOpenMP(Module &M, OpenMPInModule &OMPInModule);
+
+  /// Which OpenMP functions are called in this module?
+  SmallPtrSet<Function *, 32> OMPFuncs;
+
   /// Collection of known kernels (=GPU entry points) in the module.
   SmallPtrSet<Kernel, 8> Kernels;
 };


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