[CallGraph] Teach the CallGraph about non-leaf intrinsics.

Summary:
Currently intrinsics don't affect the creation of the call graph.
This is not accurate with respect to statepoint and patchpoint
intrinsics -- these do call (or invoke) LLVM level functions.

This change fixes this inconsistency by adding a call to the external
node for call sites that call these non-leaf intrinsics.  This coupled
with the fact that these intrinsics also escape the function pointer
they call gives us a conservatively correct call graph.

Reviewers: reames, chandlerc, atrick, pgavlin

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10526

llvm-svn: 240039

llvm/include/llvm/Analysis/CallGraph.h

@@ -56,6 +56,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Pass.h"
 #include <map>
@@ -229,7 +230,8 @@ class CallGraphNode {
   /// \brief Adds a function to the list of functions called by this one.
   void addCalledFunction(CallSite CS, CallGraphNode *M) {
     assert(!CS.getInstruction() || !CS.getCalledFunction() ||
-           !CS.getCalledFunction()->isIntrinsic());
+           !CS.getCalledFunction()->isIntrinsic() ||
+           !Intrinsic::isLeaf(CS.getCalledFunction()->getIntrinsicID()));
     CalledFunctions.emplace_back(CS.getInstruction(), M);
     M->AddRef();
   }

llvm/include/llvm/IR/Intrinsics.h

@@ -52,6 +52,11 @@ namespace Intrinsic {
   /// Returns true if the intrinsic can be overloaded.
   bool isOverloaded(ID id);
 
+  /// Returns true if the intrinsic is a leaf, i.e. it does not make any calls
+  /// itself.  Most intrinsics are leafs, the exceptions being the patchpoint
+  /// and statepoint intrinsics. These call (or invoke) their "target" argument.
+  bool isLeaf(ID id);
+
   /// Return the attributes for an intrinsic.
   AttributeSet getAttributes(LLVMContext &C, ID id);
 

llvm/lib/Analysis/IPA/CallGraph.cpp

@@ -79,8 +79,10 @@ void CallGraph::addToCallGraph(Function *F) {
       CallSite CS(cast<Value>(II));
       if (CS) {
         const Function *Callee = CS.getCalledFunction();
-        if (!Callee)
+        if (!Callee || !Intrinsic::isLeaf(Callee->getIntrinsicID()))
           // Indirect calls of intrinsics are not allowed so no need to check.
+          // We can be more precise here by using TargetArg returned by
+          // Intrinsic::isLeaf.
           Node->addCalledFunction(CS, CallsExternalNode);
         else if (!Callee->isIntrinsic())
           Node->addCalledFunction(CS, getOrInsertFunction(Callee));

llvm/lib/Analysis/IPA/CallGraphSCCPass.cpp

@@ -217,8 +217,10 @@ bool CGPassManager::RefreshCallGraph(CallGraphSCC &CurSCC,
           // another value. This can happen when constant folding happens
           // of well known functions etc.
           !CallSite(I->first) ||
-           (CallSite(I->first).getCalledFunction() &&
-            CallSite(I->first).getCalledFunction()->isIntrinsic())) {
+          (CallSite(I->first).getCalledFunction() &&
+           CallSite(I->first).getCalledFunction()->isIntrinsic() &&
+           Intrinsic::isLeaf(
+               CallSite(I->first).getCalledFunction()->getIntrinsicID()))) {
         assert(!CheckingMode &&
                "CallGraphSCCPass did not update the CallGraph correctly!");
 

llvm/lib/IR/Function.cpp

@@ -846,6 +846,18 @@ bool Intrinsic::isOverloaded(ID id) {
 #undef GET_INTRINSIC_OVERLOAD_TABLE
 }
 
+bool Intrinsic::isLeaf(ID id) {
+  switch (id) {
+  default:
+    return true;
+
+  case Intrinsic::experimental_gc_statepoint:
+  case Intrinsic::experimental_patchpoint_void:
+  case Intrinsic::experimental_patchpoint_i64:
+    return false;
+  }
+}
+
 /// This defines the "Intrinsic::getAttributes(ID id)" method.
 #define GET_INTRINSIC_ATTRIBUTES
 #include "llvm/IR/Intrinsics.gen"

llvm/test/Analysis/CallGraph/non-leaf-intrinsics.ll

@@ -0,0 +1,32 @@
+; RUN: opt -S -print-callgraph -disable-output < %s 2>&1 | FileCheck %s
+
+declare void @llvm.experimental.patchpoint.void(i64, i32, i8*, i32, ...)
+declare i32 @llvm.experimental.gc.statepoint.p0f_isVoidf(i64, i32, void ()*, i32, i32, ...)
+
+define private void @f() {
+  ret void
+}
+
+define void @calls_statepoint(i8 addrspace(1)* %arg) gc "statepoint-example" {
+entry:
+  %cast = bitcast i8 addrspace(1)* %arg to i64 addrspace(1)*
+  %safepoint_token = call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @f, i32 0, i32 0, i32 0, i32 5, i32 0, i32 0, i32 0, i32 10, i32 0, i8 addrspace(1)* %arg, i64 addrspace(1)* %cast, i8 addrspace(1)* %arg, i8 addrspace(1)* %arg)
+  ret void
+}
+
+define void @calls_patchpoint() {
+entry:
+  %c = bitcast void()* @f to i8*
+  tail call void (i64, i32, i8*, i32, ...) @llvm.experimental.patchpoint.void(i64 1, i32 15, i8* %c, i32 0, i16 65535, i16 -1, i32 65536, i32 2000000000, i32 2147483647, i32 -1, i32 4294967295, i32 4294967296, i64 2147483648, i64 4294967295, i64 4294967296, i64 -1)
+  ret void
+}
+
+
+; CHECK: Call graph node <<null function>>
+; CHECK:  CS<0x0> calls function 'f'
+
+; CHECK: Call graph node for function: 'calls_statepoint'
+; CHECK-NEXT:  CS<[[addr_0:[^>]+]]> calls external node
+
+; CHECK: Call graph node for function: 'calls_patchpoint'
+; CHECK-NEXT:  CS<[[addr_1:[^>]+]]> calls external node