From ff69509f94bcb060b56907e11b3cafcec3c66f05 Mon Sep 17 00:00:00 2001 From: Bruno Cardoso Lopes Date: Mon, 25 Aug 2014 17:51:14 +0000 Subject: [PATCH] Remove dangling initializers in GlobalDCE GlobalDCE deletes global vars and updates their initializers to nullptr while leaving underlying constants to be cleaned up later by its uses. The clean up may never happen, fix this by forcing it every time it's safe to destroy constants. Final patch by Rafael Espindola http://reviews.llvm.org/D4931 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216390 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/IPO/GlobalDCE.cpp | 8 +++++++- lib/Transforms/Utils/GlobalStatus.cpp | 3 +++ test/Transforms/GlobalDCE/deadblockaddr.ll | 16 ++++++++++++++++ 3 files changed, 26 insertions(+), 1 deletion(-) create mode 100644 test/Transforms/GlobalDCE/deadblockaddr.ll diff --git a/lib/Transforms/IPO/GlobalDCE.cpp b/lib/Transforms/IPO/GlobalDCE.cpp index 7e7a4c0ae83..e50cdb7358c 100644 --- a/lib/Transforms/IPO/GlobalDCE.cpp +++ b/lib/Transforms/IPO/GlobalDCE.cpp @@ -22,6 +22,7 @@ #include "llvm/IR/Instructions.h" #include "llvm/IR/Module.h" #include "llvm/Transforms/Utils/CtorUtils.h" +#include "llvm/Transforms/Utils/GlobalStatus.h" #include "llvm/Pass.h" using namespace llvm; @@ -141,7 +142,12 @@ bool GlobalDCE::runOnModule(Module &M) { I != E; ++I) if (!AliveGlobals.count(I)) { DeadGlobalVars.push_back(I); // Keep track of dead globals - I->setInitializer(nullptr); + if (I->hasInitializer()) { + Constant *Init = I->getInitializer(); + I->setInitializer(nullptr); + if (isSafeToDestroyConstant(Init)) + Init->destroyConstant(); + } } // The second pass drops the bodies of functions which are dead... diff --git a/lib/Transforms/Utils/GlobalStatus.cpp b/lib/Transforms/Utils/GlobalStatus.cpp index 33e34a9941e..97a0b4ee5ac 100644 --- a/lib/Transforms/Utils/GlobalStatus.cpp +++ b/lib/Transforms/Utils/GlobalStatus.cpp @@ -35,6 +35,9 @@ bool llvm::isSafeToDestroyConstant(const Constant *C) { if (isa(C)) return false; + if (isa(C) || isa(C)) + return false; + for (const User *U : C->users()) if (const Constant *CU = dyn_cast(U)) { if (!isSafeToDestroyConstant(CU)) diff --git a/test/Transforms/GlobalDCE/deadblockaddr.ll b/test/Transforms/GlobalDCE/deadblockaddr.ll new file mode 100644 index 00000000000..1ec5994d004 --- /dev/null +++ b/test/Transforms/GlobalDCE/deadblockaddr.ll @@ -0,0 +1,16 @@ +; RUN: opt -globaldce -simplifycfg -S < %s | FileCheck %s + +; Tests whether globaldce does the right cleanup while removing @bar +; so that a dead BlockAddress reference to foo won't prevent other passes +; to work properly, e.g. simplifycfg +@bar = internal unnamed_addr constant i8* blockaddress(@foo, %L1) + +; CHECK-LABEL: foo +; CHECK-NOT: br label %L1 +; CHECK: ret void +define void @foo() { +entry: + br label %L1 +L1: + ret void +} -- 2.34.1