mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-17 21:29:20 +00:00
Delete PHI nodes that are not dead but are locked in a cycle of single
useness. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19629 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
parent
b352fa5853
commit
a3fd1c569c
@ -4051,6 +4051,22 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
|
||||
PhiVal, ConstantOp);
|
||||
}
|
||||
|
||||
/// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
|
||||
/// that is dead.
|
||||
static bool DeadPHICycle(PHINode *PN, std::set<PHINode*> &PotentiallyDeadPHIs) {
|
||||
if (PN->use_empty()) return true;
|
||||
if (!PN->hasOneUse()) return false;
|
||||
|
||||
// Remember this node, and if we find the cycle, return.
|
||||
if (!PotentiallyDeadPHIs.insert(PN).second)
|
||||
return true;
|
||||
|
||||
if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
|
||||
return DeadPHICycle(PU, PotentiallyDeadPHIs);
|
||||
|
||||
return false;
|
||||
}
|
||||
|
||||
// PHINode simplification
|
||||
//
|
||||
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
|
||||
@ -4109,6 +4125,16 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
|
||||
if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
|
||||
return Result;
|
||||
|
||||
// If this is a trivial cycle in the PHI node graph, remove it. Basically, if
|
||||
// this PHI only has a single use (a PHI), and if that PHI only has one use (a
|
||||
// PHI)... break the cycle.
|
||||
if (PN.hasOneUse())
|
||||
if (PHINode *PU = dyn_cast<PHINode>(PN.use_back())) {
|
||||
std::set<PHINode*> PotentiallyDeadPHIs;
|
||||
PotentiallyDeadPHIs.insert(&PN);
|
||||
if (DeadPHICycle(PU, PotentiallyDeadPHIs))
|
||||
return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
Loading…
Reference in New Issue
Block a user