Refactor code from inlining and globalopt that checks whether a function definition is unused, and enhance it so it can tell that functions which are only used by a blockaddress are in fact dead. This probably doesn't happen much on most code, but the Linux kernel's _THIS_IP_ can trigger this issue with blockaddress. (GlobalDCE can also handle the given tescase, but we only run that at -O3.) Found while looking at PR11180.

llvm-svn: 142572

3 files changed, 4 insertions, 7 deletions

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 3552d03919b..c57e9fc0e8d 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1890,7 +1890,7 @@ bool GlobalOpt::OptimizeFunctions(Module &M) {
     if (!F->hasName() && !F->isDeclaration())
       F->setLinkage(GlobalValue::InternalLinkage);
     F->removeDeadConstantUsers();
-    if (F->use_empty() && (F->hasLocalLinkage() || F->hasLinkOnceLinkage())) {
+    if (F->isDefTriviallyDead()) {
       F->eraseFromParent();
       Changed = true;
       ++NumFnDeleted;
diff --git a/llvm/lib/Transforms/IPO/Inliner.cpp b/llvm/lib/Transforms/IPO/Inliner.cpp
index f00935b0888..bdc9fe45d34 100644
--- a/llvm/lib/Transforms/IPO/Inliner.cpp
+++ b/llvm/lib/Transforms/IPO/Inliner.cpp
@@ -533,10 +533,7 @@ bool Inliner::removeDeadFunctions(CallGraph &CG,
 
     if (DNR && DNR->count(F))
       continue;
-    if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage() &&
-        !F->hasAvailableExternallyLinkage())
-      continue;
-    if (!F->use_empty())
+    if (!F->isDefTriviallyDead())
       continue;
     
     // Remove any call graph edges from the function to its callees.
diff --git a/llvm/lib/Transforms/Utils/BasicInliner.cpp b/llvm/lib/Transforms/Utils/BasicInliner.cpp
index 23a30cc5850..50c91b6af87 100644
--- a/llvm/lib/Transforms/Utils/BasicInliner.cpp
+++ b/llvm/lib/Transforms/Utils/BasicInliner.cpp
@@ -131,8 +131,8 @@ void BasicInlinerImpl::inlineFunctions() {
         // Inline
         InlineFunctionInfo IFI(0, TD);
         if (InlineFunction(CS, IFI)) {
-          if (Callee->use_empty() && (Callee->hasLocalLinkage() ||
-                                      Callee->hasAvailableExternallyLinkage()))
+          Callee->removeDeadConstantUsers();
+          if (Callee->isDefTriviallyDead())
             DeadFunctions.insert(Callee);
           Changed = true;
           CallSites.erase(CallSites.begin() + index);