CodeGen: Assert that liveness is up to date when reading block live-ins.

Add an assert that checks whether liveins are up to date before they are
used.

- Do not print liveins into .mir files anymore in situations where they
  are out of date anyway.
- The assert in the RegisterScavenger is superseded by the new one in
  livein_begin().
- Skip parts of the liveness updating logic in IfConversion.cpp when
  liveness isn't tracked anymore (just enough to avoid hitting the new
  assert()).

Differential Revision: https://reviews.llvm.org/D27562

llvm-svn: 291169

1 files changed, 8 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 549424d257f..3869f976854 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -286,7 +286,7 @@ void MachineBasicBlock::print(raw_ostream &OS, ModuleSlotTracker &MST,
   if (!livein_empty()) {
     if (Indexes) OS << '\t';
     OS << "    Live Ins:";
-    for (const auto &LI : make_range(livein_begin(), livein_end())) {
+    for (const auto &LI : LiveIns) {
       OS << ' ' << PrintReg(LI.PhysReg, TRI);
       if (!LI.LaneMask.all())
         OS << ':' << PrintLaneMask(LI.LaneMask);
@@ -1292,3 +1292,10 @@ MachineBasicBlock::getEndClobberMask(const TargetRegisterInfo *TRI) const {
 void MachineBasicBlock::clearLiveIns() {
   LiveIns.clear();
 }
+
+MachineBasicBlock::livein_iterator MachineBasicBlock::livein_begin() const {
+  assert(getParent()->getProperties().hasProperty(
+      MachineFunctionProperties::Property::TracksLiveness) &&
+      "Liveness information is accurate");
+  return LiveIns.begin();
+}