Delete dead code after rematerializing.
LiveRangeEdit::eliminateDeadDefs() will eventually be used by coalescing,
splitting, and spilling for dead code elimination. It can delete chains of dead
instructions as long as there are no dependency loops.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127287 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp
index c4ae8c4..99d05fa 100644
--- a/lib/CodeGen/SplitKit.cpp
+++ b/lib/CodeGen/SplitKit.cpp
@@ -797,6 +797,40 @@
}
}
+void SplitEditor::deleteRematVictims() {
+ SmallVector<MachineInstr*, 8> Dead;
+ for (LiveInterval::const_vni_iterator I = Edit->getParent().vni_begin(),
+ E = Edit->getParent().vni_end(); I != E; ++I) {
+ const VNInfo *VNI = *I;
+ // Was VNI rematted anywhere?
+ if (VNI->isUnused() || VNI->isPHIDef() || !Edit->didRematerialize(VNI))
+ continue;
+ unsigned RegIdx = RegAssign.lookup(VNI->def);
+ LiveInterval *LI = Edit->get(RegIdx);
+ LiveInterval::const_iterator LII = LI->FindLiveRangeContaining(VNI->def);
+ assert(LII != LI->end() && "Missing live range for rematted def");
+
+ // Is this a dead def?
+ if (LII->end != VNI->def.getNextSlot())
+ continue;
+
+ MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
+ assert(MI && "Missing instruction for dead def");
+ MI->addRegisterDead(LI->reg, &TRI);
+
+ if (!MI->allDefsAreDead())
+ continue;
+
+ DEBUG(dbgs() << "All defs dead: " << *MI);
+ Dead.push_back(MI);
+ }
+
+ if (Dead.empty())
+ return;
+
+ Edit->eliminateDeadDefs(Dead, LIS, TII);
+}
+
void SplitEditor::finish() {
assert(OpenIdx == 0 && "Previous LI not closed before rewrite");
++NumFinished;
@@ -835,7 +869,9 @@
// Rewrite virtual registers, possibly extending ranges.
rewriteAssigned(Complex);
- // FIXME: Delete defs that were rematted everywhere.
+ // Delete defs that were rematted everywhere.
+ if (Complex)
+ deleteRematVictims();
// Get rid of unused values and set phi-kill flags.
for (LiveRangeEdit::iterator I = Edit->begin(), E = Edit->end(); I != E; ++I)