[attrs] Simplify the convergent removal to directly use the pre-built

node set rather than walking the SCC directly.

This directly exposes the functions and has already had null entries
filtered out. We also don't need need to handle optnone as it has
already been handled in the caller -- we never try to remove convergent
when there are optnone functions in the SCC.

With this change, the code for removing convergent should work with the
new pass manager and a different SCC analysis.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260668 91177308-0d34-0410-b5e6-96231b3b80d8

Author: chandlerc

lib/Transforms/IPO/FunctionAttrs.cpp

@@ -938,27 +938,18 @@ static bool addNonNullAttrs(const SCCNodeSet &SCCNodes,
 /// Removes convergent attributes where we can prove that none of the SCC's
 /// callees are themselves convergent.  Returns true if successful at removing
 /// the attribute.
-static bool removeConvergentAttrs(const CallGraphSCC &SCC,
-                                  const SCCNodeSet &SCCNodes) {
+static bool removeConvergentAttrs(const SCCNodeSet &SCCNodes) {
   // Determines whether a function can be made non-convergent, ignoring all
   // other functions in SCC.  (A function can *actually* be made non-convergent
   // only if all functions in its SCC can be made convergent.)
-  auto CanRemoveConvergent = [&](CallGraphNode *CGN) {
-    Function *F = CGN->getFunction();
-    if (!F)
-      return false;
-
+  auto CanRemoveConvergent = [&](Function *F) {
     if (!F->isConvergent())
       return true;
 
     // Can't remove convergent from declarations.
     if (F->isDeclaration())
       return false;
 
-    // Don't remove convergent from optnone functions.
-    if (F->hasFnAttribute(Attribute::OptimizeNone))
-      return false;
-
     for (Instruction &I : instructions(*F))
       if (auto CS = CallSite(&I)) {
         // Can't remove convergent if any of F's callees -- ignoring functions
@@ -979,19 +970,16 @@ static bool removeConvergentAttrs(const CallGraphSCC &SCC,
   // We can remove the convergent attr from functions in the SCC if they all
   // can be made non-convergent (because they call only non-convergent
   // functions, other than each other).
-  if (!llvm::all_of(SCC, CanRemoveConvergent))
+  if (!llvm::all_of(SCCNodes, CanRemoveConvergent))
     return false;
 
-  // If we got here, all of the SCC's callees are non-convergent, and none of
-  // the optnone functions in the SCC are marked as convergent.  Therefore all
+  // If we got here, all of the SCC's callees are non-convergent. Therefore all
   // of the SCC's functions can be marked as non-convergent.
-  for (CallGraphNode *CGN : SCC)
-    if (Function *F = CGN->getFunction()) {
-      if (F->isConvergent())
-        DEBUG(dbgs() << "Removing convergent attr from " << F->getName()
-                     << "\n");
-      F->setNotConvergent();
-    }
+  for (Function *F : SCCNodes) {
+    if (F->isConvergent())
+      DEBUG(dbgs() << "Removing convergent attr from " << F->getName() << "\n");
+    F->setNotConvergent();
+  }
   return true;
 }
 
@@ -1071,7 +1059,7 @@ bool PostOrderFunctionAttrs::runOnSCC(CallGraphSCC &SCC) {
   if (!ExternalNode) {
     Changed |= addNoAliasAttrs(SCCNodes);
     Changed |= addNonNullAttrs(SCCNodes, *TLI);
-    Changed |= removeConvergentAttrs(SCC, SCCNodes);
+    Changed |= removeConvergentAttrs(SCCNodes);
   }
 
   Changed |= addNoRecurseAttrs(SCC);