Option to ignore assume like intrinsic uses in hasAddressTaken()

[arsenm]

llvm/include/llvm/IR/Function.h

880

true may be a better default?

[rampitec]

llvm/include/llvm/IR/Function.h

880

It probably is. I want to preserve current behavior and then we can switch the default.

[rampitec]

Fixed bug if cast is unused.

[rampitec]

llvm/include/llvm/IR/Function.h

880

D96179

[rampitec]

Ping.

[madhur13490]

llvm/lib/IR/Function.cpp

1582

Please update this comment with a clear description of the new bool.

[rampitec]

Updated comment.

[rampitec]

Ping

[rampitec]

ping

llvm/include/llvm/IR/Function.h

/// @}
   void dropAllReferences();
 
   /// hasAddressTaken - returns true if there are any uses of this function
   /// other than direct calls or invokes to it, or blockaddress expressions.
   /// Optionally passes back an offending user for diagnostic purposes and
   /// ignores callback uses.
   ///
   bool hasAddressTaken(const User ** = nullptr,
-                       bool IgnoreCallbackUses = false) const;
+                       bool IgnoreCallbackUses = false,
+                       bool IgnoreAssumeLikeCalls = false) const;
 
   /// isDefTriviallyDead - Return true if it is trivially safe to remove
   /// this function definition from the module (because it isn't externally
   /// visible, does not have its address taken, and has no callers).  To make
   /// this more accurate, call removeDeadConstantUsers first.
   bool isDefTriviallyDead() const;
 
   /// callsFunctionThatReturnsTwice - Return true if the function has a call to

llvm/lib/Analysis/CallGraph.cpp

 }
 
 void CallGraph::addToCallGraph(Function *F) {
   CallGraphNode *Node = getOrInsertFunction(F);
 
   // If this function has external linkage or has its address taken and
   // it is not a callback, then anything could call it.
   if (!F->hasLocalLinkage() ||
-      F->hasAddressTaken(nullptr, /*IgnoreCallbackUses=*/true))
+      F->hasAddressTaken(nullptr, /*IgnoreCallbackUses=*/true,
+                         /* IgnoreAssumeLikeCalls */ true))
     ExternalCallingNode->addCalledFunction(nullptr, Node);
 
   populateCallGraphNode(Node);
 }
 
 void CallGraph::populateCallGraphNode(CallGraphNode *Node) {
   Function *F = Node->getFunction();
 

llvm/lib/IR/Function.cpp

 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/IntrinsicsAArch64.h"
 #include "llvm/IR/IntrinsicsAMDGPU.h"
 #include "llvm/IR/IntrinsicsARM.h"
 #include "llvm/IR/IntrinsicsBPF.h"
 #include "llvm/IR/IntrinsicsHexagon.h"
 #include "llvm/IR/IntrinsicsMips.h"
 #include "llvm/IR/IntrinsicsNVPTX.h"
Optional<Function *> Intrinsic::remangleIntrinsicFunction(Function *F) {
   NewDecl->setCallingConv(F->getCallingConv());
   assert(NewDecl->getFunctionType() == F->getFunctionType() &&
          "Shouldn't change the signature");
   return NewDecl;
 }
 
 /// hasAddressTaken - returns true if there are any uses of this function
 /// other than direct calls or invokes to it. Optionally ignores callback
 /// uses.
 bool Function::hasAddressTaken(const User **PutOffender,
-                               bool IgnoreCallbackUses) const {
+                               bool IgnoreCallbackUses,
+                               bool IgnoreAssumeLikeCalls) const {
   for (const Use &U : uses()) {
     const User *FU = U.getUser();
     if (isa<BlockAddress>(FU))
       continue;
 
     if (IgnoreCallbackUses) {
       AbstractCallSite ACS(&U);
       if (ACS && ACS.isCallbackCall())
         continue;
     }
 
     const auto *Call = dyn_cast<CallBase>(FU);
     if (!Call) {
+      if (IgnoreAssumeLikeCalls) {
+        if (const auto *FI = dyn_cast<Instruction>(FU)) {
+          if (FI->isCast() &&
+              llvm::all_of(FU->users(), [](const User *U) {
+                if (const auto *I = dyn_cast<IntrinsicInst>(U))
+                  return I->isAssumeLikeIntrinsic();
+                return false;
+              }))
+            continue;
+        }
+      }
       if (PutOffender)
         *PutOffender = FU;
       return true;
     }
     if (!Call->isCallee(&U)) {
       if (PutOffender)
         *PutOffender = FU;
       return true;

llvm/test/Analysis/CallGraph/ignore-assumelike-calls.ll

+; RUN: opt < %s -print-callgraph -disable-output 2>&1 | FileCheck %s
+; CHECK: Call graph node <<null function>><<{{.*}}>>  #uses=0
+; CHECK-NEXT:   CS<None> calls function 'llvm.lifetime.start.p0i8'
+; CHECK-EMPTY:
+; CHECK-NEXT:   Call graph node for function: 'f'<<{{.*}}>>  #uses=0
+; CHECK-EMPTY:
+; CHECK-NEXT:   Call graph node for function: 'llvm.lifetime.start.p0i8'<<{{.*}}>>  #uses=1
+; CHECK-EMPTY:
+
+define internal void @f() {
+entry:
+  %c = bitcast void()* @f to i8*
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* %c)
+  ret void
+}
+
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)