[CallGraphUpdater] Removed references to calles when deleting function

[sdmitriev]

Summary

Otherwise we can get unaccounted references to call graph nodes.

[jdoerfert]

LGTM. Thanks!

(I think the other actions on the old CG have to be cached as well, I have some patches locally I have to clean up).

llvm/lib/Transforms/Utils/CallGraphUpdater.cpp

void CallGraphUpdater::removeFunction(Function &DeadFn) {
   DeadFn.deleteBody();
   DeadFn.setLinkage(GlobalValue::ExternalLinkage);
   if (DeadFn.hasComdat())
     DeadFunctionsInComdats.push_back(&DeadFn);
   else
     DeadFunctions.push_back(&DeadFn);
 
   // For the old call graph we remove the function from the SCC right away.
-  if (CG && !ReplacedFunctions.count(&DeadFn))
-    CGSCC->DeleteNode((*CG)[&DeadFn]);
+  if (CG && !ReplacedFunctions.count(&DeadFn)) {
+    CallGraphNode *DeadCGN = (*CG)[&DeadFn];
+    DeadCGN->removeAllCalledFunctions();
+    CGSCC->DeleteNode(DeadCGN);
+  }
 }
 
 void CallGraphUpdater::replaceFunctionWith(Function &OldFn, Function &NewFn) {
   OldFn.removeDeadConstantUsers();
   ReplacedFunctions.insert(&OldFn);
   if (CG) {
     // Update the call graph for the newly promoted function.
     CallGraphNode *OldCGN = (*CG)[&OldFn];

llvm/test/Transforms/Util/cg-updater-dead-function-callees.ll

+; RUN: opt -inline -attributor-cgscc -tailcallelim -S %s | FileCheck %s
+;
+; CHECK: define void @foo()
+; CHECK: declare i32 @baz()
+; CHECK-NOT: void @goo()
+; CHECK-NOT: void @bar()
+
+define void @foo() {
+  call fastcc void @bar()
+  ret void
+}
+
+define internal fastcc void @goo() {
+  call fastcc void @bar()
+  ret void
+}
+
+define internal fastcc void @bar() {
+  %call = call i32 @baz()
+  %cond = icmp eq i32 %call, 0
+  br i1 %cond, label %if.then, label %if.end
+
+if.then:
+  call fastcc void @goo()
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+declare i32 @baz()

llvm/unittests/IR/LegacyPassManagerTest.cpp

TEST(PassManager, CallGraphUpdater0) {
       Function *SF = splitSimpleFunction(*F);
       CallInst::Create(F, "", &SF->getEntryBlock());
       ASSERT_EQ(M->getFunctionList().size(), 5U);
       CGModifierPass *P = new CGModifierPass();
       legacy::PassManager Passes;
       Passes.add(P);
       Passes.run(*M);
       ASSERT_EQ(P->SetupWorked, 1U);
-      ASSERT_EQ(P->NumSCCs, 5U);
-      ASSERT_EQ(P->NumFns, 8U);
-      ASSERT_EQ(P->NumFnDecls, 3U);
+      ASSERT_EQ(P->NumSCCs, 4U);
+      ASSERT_EQ(P->NumFns, 6U);
+      ASSERT_EQ(P->NumFnDecls, 1U);
       ASSERT_EQ(M->getFunctionList().size(), 3U);
       ASSERT_EQ(P->NumExtCalledBefore, /* test1, 2a, 2b, 3, 4 */ 5U);
       ASSERT_EQ(P->NumExtCalledAfter, /* test1, 3repl, 4 */ 3U);
     }
   }
 }
 
 INITIALIZE_PASS(ModuleNDM, "mndm", "mndm", false, false)
 INITIALIZE_PASS_BEGIN(CGPass, "cgp","cgp", false, false)
 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
 INITIALIZE_PASS_END(CGPass, "cgp","cgp", false, false)
 INITIALIZE_PASS(FPass, "fp","fp", false, false)
 INITIALIZE_PASS_BEGIN(LPass, "lp","lp", false, false)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 INITIALIZE_PASS_END(LPass, "lp","lp", false, false)