Teach PHIElimination to split critical edges when -split-phi-edges is enabled.
Critical edges leading to a PHI node are split when the PHI source variable is
live out from the predecessor block. This help the coalescer eliminate more
PHI joins.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86725 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index 96c655c..1580667 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -50,6 +50,14 @@
MachineFunctionPass::getAnalysisUsage(AU);
}
+MachineInstr *
+LiveVariables::VarInfo::findKill(const MachineBasicBlock *MBB) const {
+ for (unsigned i = 0, e = Kills.size(); i != e; ++i)
+ if (Kills[i]->getParent() == MBB)
+ return Kills[i];
+ return NULL;
+}
+
void LiveVariables::VarInfo::dump() const {
errs() << " Alive in blocks: ";
for (SparseBitVector<>::iterator I = AliveBlocks.begin(),
@@ -641,3 +649,35 @@
PHIVarInfo[BBI->getOperand(i + 1).getMBB()->getNumber()]
.push_back(BBI->getOperand(i).getReg());
}
+
+void LiveVariables::addNewBlock(MachineBasicBlock *A, MachineBasicBlock *B) {
+ unsigned NumA = A->getNumber();
+ unsigned NumB = B->getNumber();
+
+ // Update info for all live variables
+ for (unsigned i = 0, e = VirtRegInfo.size(); i != e; ++i) {
+ VarInfo &VI = VirtRegInfo[i];
+
+ // Anything live through B is also live through A.
+ if (VI.AliveBlocks.test(NumB)) {
+ VI.AliveBlocks.set(NumA);
+ continue;
+ }
+
+ // If we're not killed in B, we are not live in
+ if (!VI.findKill(B))
+ continue;
+
+ unsigned Reg = i+TargetRegisterInfo::FirstVirtualRegister;
+
+ // Find a def outside B
+ for (MachineRegisterInfo::def_iterator di = MRI->def_begin(Reg),
+ de=MRI->def_end(); di != de; ++di) {
+ if (di->getParent() != B) {
+ // Reg was defined outside B and killed in B - it must be live in.
+ VI.AliveBlocks.set(NumA);
+ break;
+ }
+ }
+ }
+}