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Rework GlobalValue::removeDeadConstantUsers to always remove dead constant
exprs hanging off a global, even if the global is not otherwise dead. This requires some tricky iterator gymnastics. This implements Transforms/GlobalOpt/constantexpr-dangle.ll by deleting a constantexpr that made it appear that the address of the function was taken. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34608 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -128,10 +128,6 @@ public:
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/// off of this global value, remove them. This method is useful for clients
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/// off of this global value, remove them. This method is useful for clients
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/// that want to check to see if a global is unused, but don't want to deal
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/// that want to check to see if a global is unused, but don't want to deal
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/// with potentially dead constants hanging off of the globals.
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/// with potentially dead constants hanging off of the globals.
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///
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/// This method tries to make the global dead. If it detects a user that
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/// would prevent it from becoming completely dead, it gives up early,
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/// potentially leaving some dead constant users around.
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void removeDeadConstantUsers();
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void removeDeadConstantUsers();
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// Methods for support type inquiry through isa, cast, and dyn_cast:
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// Methods for support type inquiry through isa, cast, and dyn_cast:
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@ -22,20 +22,18 @@ using namespace llvm;
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// GlobalValue Class
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// GlobalValue Class
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//===----------------------------------------------------------------------===//
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//===----------------------------------------------------------------------===//
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/// This could be named "SafeToDestroyGlobalValue". It just makes sure that
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/// removeDeadUsersOfConstant - If the specified constantexpr is dead, remove
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/// there are no non-constant uses of this GlobalValue. If there aren't then
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/// it. This involves recursively eliminating any dead users of the
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/// this and the transitive closure of the constants can be deleted. See the
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/// constantexpr.
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/// destructor for details.
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static bool removeDeadUsersOfConstant(Constant *C) {
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static bool removeDeadConstantUsers(Constant* C) {
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if (isa<GlobalValue>(C)) return false; // Cannot remove this
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if (isa<GlobalValue>(C)) return false; // Cannot remove this
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while (!C->use_empty())
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while (!C->use_empty()) {
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if (Constant *User = dyn_cast<Constant>(C->use_back())) {
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Constant *User = dyn_cast<Constant>(C->use_back());
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if (!removeDeadConstantUsers(User))
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if (!User) return false; // Non-constant usage;
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return false; // Constant wasn't dead
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if (!removeDeadUsersOfConstant(User))
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} else {
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return false; // Constant wasn't dead
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return false; // Non-constant usage;
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}
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}
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C->destroyConstant();
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C->destroyConstant();
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return true;
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return true;
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@ -45,17 +43,27 @@ static bool removeDeadConstantUsers(Constant* C) {
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/// off of this global value, remove them. This method is useful for clients
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/// off of this global value, remove them. This method is useful for clients
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/// that want to check to see if a global is unused, but don't want to deal
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/// that want to check to see if a global is unused, but don't want to deal
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/// with potentially dead constants hanging off of the globals.
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/// with potentially dead constants hanging off of the globals.
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///
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/// This function returns true if the global value is now dead. If all
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/// users of this global are not dead, this method may return false and
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/// leave some of them around.
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void GlobalValue::removeDeadConstantUsers() {
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void GlobalValue::removeDeadConstantUsers() {
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while(!use_empty()) {
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if (Constant* User = dyn_cast<Constant>(use_back())) {
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Value::use_iterator I = use_begin(), E = use_end();
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if (!::removeDeadConstantUsers(User))
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Value::use_iterator LastNonDeadUser = E;
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return; // Constant wasn't dead
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for (; I != E; ++I) {
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if (Constant *User = dyn_cast<Constant>(*I)) {
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if (!removeDeadUsersOfConstant(User)) {
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// If the constant wasn't dead, remember that this was the last live use
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// and move on to the next constant.
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LastNonDeadUser = I;
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} else {
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// If the constant was dead, then the iterator is invalidated.
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if (LastNonDeadUser == E) {
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I = use_begin();
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if (I == E) break;
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} else {
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I = LastNonDeadUser;
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}
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}
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} else {
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} else {
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return; // Non-constant usage;
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LastNonDeadUser = I;
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}
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}
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}
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}
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}
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}
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