vendor/llvm/llvm-trunk-r366426

1 files changed, 27 insertions, 43 deletions

diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index 11efe95b10d4..3a08069dcd4a 100644
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -1,9 +1,8 @@
 //===- MergeFunctions.cpp - Merge identical functions ---------------------===//
 //
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
@@ -190,8 +189,6 @@ public:
   void replaceBy(Function *G) const {
     F = G;
   }
-
-  void release() { F = nullptr; }
 };
 
 /// MergeFunctions finds functions which will generate identical machine code,
@@ -281,8 +278,8 @@ private:
   // Replace G with an alias to F (deleting function G)
   void writeAlias(Function *F, Function *G);
 
-  // Replace G with an alias to F if possible, or a thunk to F if
-  // profitable. Returns false if neither is the case.
+  // Replace G with an alias to F if possible, or a thunk to F if possible.
+  // Returns false if neither is the case.
   bool writeThunkOrAlias(Function *F, Function *G);
 
   /// Replace function F with function G in the function tree.
@@ -383,6 +380,11 @@ bool MergeFunctions::doSanityCheck(std::vector<WeakTrackingVH> &Worklist) {
 }
 #endif
 
+/// Check whether \p F is eligible for function merging.
+static bool isEligibleForMerging(Function &F) {
+  return !F.isDeclaration() && !F.hasAvailableExternallyLinkage();
+}
+
 bool MergeFunctions::runOnModule(Module &M) {
   if (skipModule(M))
     return false;
@@ -394,17 +396,12 @@ bool MergeFunctions::runOnModule(Module &M) {
   std::vector<std::pair<FunctionComparator::FunctionHash, Function *>>
     HashedFuncs;
   for (Function &Func : M) {
-    if (!Func.isDeclaration() && !Func.hasAvailableExternallyLinkage()) {
+    if (isEligibleForMerging(Func)) {
       HashedFuncs.push_back({FunctionComparator::functionHash(Func), &Func});
     }
   }
 
-  std::stable_sort(
-      HashedFuncs.begin(), HashedFuncs.end(),
-      [](const std::pair<FunctionComparator::FunctionHash, Function *> &a,
-         const std::pair<FunctionComparator::FunctionHash, Function *> &b) {
-        return a.first < b.first;
-      });
+  llvm::stable_sort(HashedFuncs, less_first());
 
   auto S = HashedFuncs.begin();
   for (auto I = HashedFuncs.begin(), IE = HashedFuncs.end(); I != IE; ++I) {
@@ -654,12 +651,16 @@ void MergeFunctions::filterInstsUnrelatedToPDI(
   LLVM_DEBUG(dbgs() << " }\n");
 }
 
-// Don't merge tiny functions using a thunk, since it can just end up
-// making the function larger.
-static bool isThunkProfitable(Function * F) {
+/// Whether this function may be replaced by a forwarding thunk.
+static bool canCreateThunkFor(Function *F) {
+  if (F->isVarArg())
+    return false;
+
+  // Don't merge tiny functions using a thunk, since it can just end up
+  // making the function larger.
   if (F->size() == 1) {
     if (F->front().size() <= 2) {
-      LLVM_DEBUG(dbgs() << "isThunkProfitable: " << F->getName()
+      LLVM_DEBUG(dbgs() << "canCreateThunkFor: " << F->getName()
                         << " is too small to bother creating a thunk for\n");
       return false;
     }
@@ -695,6 +696,7 @@ void MergeFunctions::writeThunk(Function *F, Function *G) {
   } else {
     NewG = Function::Create(G->getFunctionType(), G->getLinkage(),
                             G->getAddressSpace(), "", G->getParent());
+    NewG->setComdat(G->getComdat());
     BB = BasicBlock::Create(F->getContext(), "", NewG);
   }
 
@@ -787,7 +789,7 @@ bool MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
     writeAlias(F, G);
     return true;
   }
-  if (isThunkProfitable(F)) {
+  if (canCreateThunkFor(F)) {
     writeThunk(F, G);
     return true;
   }
@@ -802,9 +804,9 @@ void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
     // Both writeThunkOrAlias() calls below must succeed, either because we can
     // create aliases for G and NewF, or because a thunk for F is profitable.
     // F here has the same signature as NewF below, so that's what we check.
-    if (!isThunkProfitable(F) && (!canCreateAliasFor(F) || !canCreateAliasFor(G))) {
+    if (!canCreateThunkFor(F) &&
+        (!canCreateAliasFor(F) || !canCreateAliasFor(G)))
       return;
-    }
 
     // Make them both thunks to the same internal function.
     Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
@@ -944,25 +946,7 @@ void MergeFunctions::remove(Function *F) {
 // For each instruction used by the value, remove() the function that contains
 // the instruction. This should happen right before a call to RAUW.
 void MergeFunctions::removeUsers(Value *V) {
-  std::vector<Value *> Worklist;
-  Worklist.push_back(V);
-  SmallPtrSet<Value*, 8> Visited;
-  Visited.insert(V);
-  while (!Worklist.empty()) {
-    Value *V = Worklist.back();
-    Worklist.pop_back();
-
-    for (User *U : V->users()) {
-      if (Instruction *I = dyn_cast<Instruction>(U)) {
-        remove(I->getFunction());
-      } else if (isa<GlobalValue>(U)) {
-        // do nothing
-      } else if (Constant *C = dyn_cast<Constant>(U)) {
-        for (User *UU : C->users()) {
-          if (!Visited.insert(UU).second)
-            Worklist.push_back(UU);
-        }
-      }
-    }
-  }
+  for (User *U : V->users())
+    if (auto *I = dyn_cast<Instruction>(U))
+      remove(I->getFunction());
 }