GlobalOpt only process non constant local GVs while optimizing global vars.
If non constant local GV named A is used by a constant local GV named B (e.g. llvm.dbg.variable) and B is not used by anyone else then eliminate A as well as B.
In other words, debug info should not interfere in removal of unused GV.
--This life, and those below, will be ignored--
M test/Transforms/GlobalOpt/2009-03-03-dbg.ll
M lib/Transforms/IPO/GlobalOpt.cpp
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66167 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index 0a35fa9..9284500 100644
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -137,17 +137,28 @@
}
/// ConstantIsDead - Return true if the specified constant is (transitively)
-/// dead. The constant may be used by other constants (e.g. constant arrays and
-/// constant exprs) as long as they are dead, but it cannot be used by anything
-/// else.
-static bool ConstantIsDead(Constant *C) {
+/// dead. The constant may be used by other constants (e.g. constant arrays,
+/// constant exprs, constant global variables) as long as they are dead,
+/// but it cannot be used by anything else. If DeadGVs is not null then
+/// record dead constant GV users.
+static bool ConstantIsDead(Constant *C,
+ SmallPtrSet<GlobalVariable *, 4> *DeadGVs = false) {
if (isa<GlobalValue>(C)) return false;
- for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
- if (Constant *CU = dyn_cast<Constant>(*UI)) {
- if (!ConstantIsDead(CU)) return false;
+ for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI) {
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(*UI)) {
+ if (!GV->isConstant() || !GV->hasLocalLinkage() || !GV->use_empty())
+ return false;
+ else {
+ if (DeadGVs)
+ DeadGVs->insert(GV);
+ }
+ }
+ else if (Constant *CU = dyn_cast<Constant>(*UI)) {
+ if (!ConstantIsDead(CU, DeadGVs)) return false;
} else
return false;
+ }
return true;
}
@@ -338,8 +349,19 @@
} else if (Constant *C = dyn_cast<Constant>(U)) {
// If we have a chain of dead constantexprs or other things dangling from
// us, and if they are all dead, nuke them without remorse.
- if (ConstantIsDead(C)) {
- C->destroyConstant();
+ SmallPtrSet<GlobalVariable *, 4> DeadGVs;
+ if (ConstantIsDead(C, &DeadGVs)) {
+ for (SmallPtrSet<GlobalVariable *, 4>::iterator TI = DeadGVs.begin(),
+ TE = DeadGVs.end(); TI != TE; ) {
+ GlobalVariable *TGV = *TI; ++TI;
+ if (TGV == C)
+ C = NULL;
+ TGV->eraseFromParent();
+ }
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
+ GV->eraseFromParent();
+ else if (C)
+ C->destroyConstant();
// This could have invalidated UI, start over from scratch.
CleanupConstantGlobalUsers(V, Init);
return true;