[PATCH] D66155: [Attributor] Liveness for internal functions.

[Stefan Stipanovic via Phabricator via llvm-commits]

sstefan1 created this revision.
sstefan1 added reviewers: jdoerfert, uenoku.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

For an internal function, if all its call sites are dead, the body of the function is considered dead. This patch also updates checkForAllCallSites with llvm::function_ref.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D66155

Files:
  llvm/include/llvm/Transforms/IPO/Attributor.h
  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
@@ -1043,7 +1043,7 @@
   unsigned ArgNo = getArgNo();
 
   // Callback function
-  std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
+  auto CallSiteCheck = [&](CallSite CS) {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
     auto *NonNullAA =
@@ -1245,6 +1245,11 @@
   void initialize(Attributor &A) override {
     const Function &F = getAnchorScope();
 
+    if (F.hasInternalLinkage()) {
+      LLVM_DEBUG(dbgs() << "[INIT] skipped internal function\n");
+      return;
+    }
+
     ToBeExploredPaths.insert(&(F.getEntryBlock().front()));
     AssumedLiveBlocks.insert(&(F.getEntryBlock()));
     for (size_t i = 0; i < ToBeExploredPaths.size(); ++i)
@@ -1467,10 +1472,32 @@
 }
 
 ChangeStatus AAIsDeadImpl::updateImpl(Attributor &A) {
+  Function &F = getAnchorScope();
+  ChangeStatus Status = ChangeStatus::UNCHANGED;
+
+  if (F.hasInternalLinkage()) {
+    auto CallSiteCheck = [&](CallSite) { return false; };
+
+    // All callsites of F are dead.
+    if (A.checkForAllCallSites(F, CallSiteCheck, *this, true)){
+      LLVM_DEBUG(dbgs() << "[UPDATEIMPL] All call sites are dead\n");
+      return ChangeStatus::UNCHANGED;
+    }
+
+    // There exists at least one live call site, so we explore the function.
+
+    Status = ChangeStatus::CHANGED;
+    ToBeExploredPaths.insert(&(F.getEntryBlock().front()));
+    AssumedLiveBlocks.insert(&(F.getEntryBlock()));
+    for (size_t i = 0; i < ToBeExploredPaths.size(); ++i)
+      if (const Instruction *NextNoReturnI =
+              findNextNoReturn(A, ToBeExploredPaths[i]))
+        NoReturnCalls.insert(NextNoReturnI);
+  }
+
   // Temporary collection to iterate over existing noreturn instructions. This
   // will alow easier modification of NoReturnCalls collection
   SmallVector<const Instruction *, 8> NoReturnChanged;
-  ChangeStatus Status = ChangeStatus::UNCHANGED;
 
   for (const Instruction *I : NoReturnCalls)
     NoReturnChanged.push_back(I);
@@ -1774,7 +1801,7 @@
   bool IsGlobal = isAssumedGlobal();
 
   // Callback function
-  std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) -> bool {
+  auto CallSiteCheck = [&](CallSite CS) {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
     // Check that DereferenceableAA is AADereferenceableCallSiteArgument.
@@ -1950,7 +1977,7 @@
   auto BeforeState = getAssumed();
 
   // Callback function
-  std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
+  auto CallSiteCheck = [&](CallSite CS) {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
     auto *AlignAA = A.getAAFor<AAAlign>(*this, *CS.getInstruction(), ArgNo);
@@ -2056,7 +2083,7 @@
 /// ----------------------------------------------------------------------------
 
 bool Attributor::checkForAllCallSites(Function &F,
-                                      std::function<bool(CallSite)> &Pred,
+                                      const function_ref<bool(CallSite)> &Pred,
                                       const AbstractAttribute &QueryingAA,
                                       bool RequireAllCallSites) {
   // We can try to determine information from
Index: llvm/include/llvm/Transforms/IPO/Attributor.h
===================================================================
--- llvm/include/llvm/Transforms/IPO/Attributor.h
+++ llvm/include/llvm/Transforms/IPO/Attributor.h
@@ -321,7 +321,8 @@
   /// This method will evaluate \p Pred on call sites and return
   /// true if \p Pred holds in every call sites. However, this is only possible
   /// all call sites are known, hence the function has internal linkage.
-  bool checkForAllCallSites(Function &F, std::function<bool(CallSite)> &Pred,
+  bool checkForAllCallSites(Function &F,
+                            const function_ref<bool(CallSite)> &Pred,
                             const AbstractAttribute &QueryingAA,
                             bool RequireAllCallSites);
 


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