[NFC][CodeGen] Cleanup lifetime in StackColoring instead of DeadMachineInstructionElim

Author: Ralender

llvm/lib/CodeGen/MachineInstr.cpp

@@ -1417,10 +1417,6 @@ bool MachineInstr::isDead(const MachineRegisterInfo &MRI,
   if (isInlineAsm())
     return false;
 
-  // FIXME: See issue #105950 for why LIFETIME markers are considered dead here.
-  if (isLifetimeMarker())
-    return true;
-
   // If there are no defs with uses, then we call the instruction dead so long
   // as we do not suspect it may have sideeffects.
   return wouldBeTriviallyDead();

llvm/lib/CodeGen/StackColoring.cpp

@@ -656,8 +656,10 @@ unsigned StackColoring::collectMarkers(unsigned NumSlot) {
       if (MI.getOpcode() == TargetOpcode::LIFETIME_START ||
           MI.getOpcode() == TargetOpcode::LIFETIME_END) {
         int Slot = getStartOrEndSlot(MI);
-        if (Slot < 0)
+        if (Slot < 0) {
+          Markers.push_back(&MI);
           continue;
+        }
         InterestingSlots.set(Slot);
         if (MI.getOpcode() == TargetOpcode::LIFETIME_START) {
           BetweenStartEnd.set(Slot);
@@ -896,6 +898,18 @@ bool StackColoring::removeAllMarkers() {
   }
   Markers.clear();
 
+  for (MachineBasicBlock &MBB : *MF) {
+    if (BlockLiveness.contains(&MBB))
+      continue;
+    for (MachineInstr &MI : make_early_inc_range(MBB)) {
+      if (MI.getOpcode() == TargetOpcode::LIFETIME_START ||
+          MI.getOpcode() == TargetOpcode::LIFETIME_END) {
+        Count++;
+        MI.eraseFromParent();
+      }
+    }
+  }
+
   LLVM_DEBUG(dbgs() << "Removed " << Count << " markers.\n");
   return Count;
 }
@@ -1216,8 +1230,8 @@ bool StackColoring::run(MachineFunction &Func) {
   unsigned NumSlots = MFI->getObjectIndexEnd();
 
   // If there are no stack slots then there are no markers to remove.
-  if (!NumSlots)
-    return false;
+  if (!NumSlots || DisableColoring)
+    return removeAllMarkers();
 
   SmallVector<int, 8> SortedSlots;
   SortedSlots.reserve(NumSlots);
@@ -1241,7 +1255,7 @@ bool StackColoring::run(MachineFunction &Func) {
 
   // Don't continue because there are not enough lifetime markers, or the
   // stack is too small, or we are told not to optimize the slots.
-  if (NumMarkers < 2 || TotalSize < 16 || DisableColoring) {
+  if (NumMarkers < 2 || TotalSize < 16) {
     LLVM_DEBUG(dbgs() << "Will not try to merge slots.\n");
     return removeAllMarkers();
   }

llvm/test/CodeGen/X86/StackColoring.ll

@@ -581,6 +581,41 @@ onerr:
 
 %Data = type { [32 x i64] }
 
+declare void @throw()
+
+declare i32 @__CxxFrameHandler3(...)
+
+declare void @llvm.trap()
+
+;CHECK-LABEL: removed_all_lifetime:
+;YESCOLOR-NOT: LIFETIME_END
+;NOFIRSTUSE-NOT: LIFETIME_END
+;NOCOLOR-NOT: LIFETIME_END
+define void @removed_all_lifetime() personality ptr @__CxxFrameHandler3 {
+entry:
+  %alloca2 = alloca ptr, align 4
+  %alloca1 = alloca ptr, align 4
+  store volatile ptr null, ptr %alloca1
+  invoke void @throw()
+          to label %unreachable unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %entry
+  %cs = catchswitch within none [label %catch.pad] unwind to caller
+
+catch.pad:                                        ; preds = %catch.dispatch
+  %cp = catchpad within %cs [ptr null, i32 0, ptr %alloca1]
+  %v = load volatile ptr, ptr %alloca1
+  store volatile ptr null, ptr %alloca1
+  call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %alloca1)
+  call void @llvm.lifetime.start.p0(i64 4, ptr %alloca2)
+  store volatile ptr null, ptr %alloca1
+  call void @llvm.trap()
+  unreachable
+
+unreachable:                                      ; preds = %entry
+  unreachable
+}
+
 declare void @destructor()
 
 declare void @inita(ptr)