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GlobalOpt: Don't drop unused memberes of a Comdat

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A linkonce_odr member of a COMDAT shouldn't be dropped if we need to
keep the entire COMDAT group.

This fixes PR21191.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219283 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-10-08 07:23:31 +00:00
parent f8b5847bc4
commit b07b0970b1
2 changed files with 39 additions and 8 deletions
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28
lib/Transforms/IPO/GlobalOpt.cpp
View File

@ -88,6 +88,7 @@ namespace {
const DataLayout *DL;
TargetLibraryInfo *TLI;
SmallSet<const Comdat *, 8> NotDiscardableComdats;
};
}
@ -1908,8 +1909,11 @@ bool GlobalOpt::OptimizeFunctions(Module &M) {
// Functions without names cannot be referenced outside this module.
if (!F->hasName() && !F->isDeclaration() && !F->hasLocalLinkage())
F->setLinkage(GlobalValue::InternalLinkage);
const Comdat *C = F->getComdat();
bool inComdat = C && NotDiscardableComdats.count(C);
F->removeDeadConstantUsers();
if (F->isDefTriviallyDead()) {
if ((!inComdat || F->hasLocalLinkage()) && F->isDefTriviallyDead()) {
F->eraseFromParent();
Changed = true;
++NumFnDeleted;
@ -1941,12 +1945,6 @@ bool GlobalOpt::OptimizeFunctions(Module &M) {
bool GlobalOpt::OptimizeGlobalVars(Module &M) {
bool Changed = false;
SmallSet<const Comdat *, 8> NotDiscardableComdats;
for (const GlobalVariable &GV : M.globals())
if (const Comdat *C = GV.getComdat())
if (!GV.isDiscardableIfUnused())
NotDiscardableComdats.insert(C);
for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
GVI != E; ) {
GlobalVariable *GV = GVI++;
@ -1963,7 +1961,7 @@ bool GlobalOpt::OptimizeGlobalVars(Module &M) {
if (GV->isDiscardableIfUnused()) {
if (const Comdat *C = GV->getComdat())
if (NotDiscardableComdats.count(C))
if (NotDiscardableComdats.count(C) && !GV->hasLocalLinkage())
continue;
Changed |= ProcessGlobal(GV, GVI);
}
@ -3047,6 +3045,20 @@ bool GlobalOpt::runOnModule(Module &M) {
while (LocalChange) {
LocalChange = false;
NotDiscardableComdats.clear();
for (const GlobalVariable &GV : M.globals())
if (const Comdat *C = GV.getComdat())
if (!GV.isDiscardableIfUnused() || !GV.use_empty())
NotDiscardableComdats.insert(C);
for (Function &F : M)
if (const Comdat *C = F.getComdat())
if (!F.isDefTriviallyDead())
NotDiscardableComdats.insert(C);
for (GlobalAlias &GA : M.aliases())
if (const Comdat *C = GA.getComdat())
if (!GA.isDiscardableIfUnused() || !GA.use_empty())
NotDiscardableComdats.insert(C);
// Delete functions that are trivially dead, ccc -> fastcc
LocalChange |= OptimizeFunctions(M);

19
test/Transforms/GlobalOpt/pr21191.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: opt < %s -globalopt -S | FileCheck %s
$c = comdat any
; CHECK: $c = comdat any
define linkonce_odr void @foo() comdat $c {
ret void
}
; CHECK: define linkonce_odr void @foo() comdat $c
define linkonce_odr void @bar() comdat $c {
ret void
}
; CHECK: define linkonce_odr void @bar() comdat $c
define void @zed() {
call void @foo()
ret void
}