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  are out of date anyway.
- The assert in the RegisterScavenger is superseded by the new one in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, 0 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/RegisterScavenging.cpp b/llvm/lib/CodeGen/RegisterScavenging.cpp
index de1c35caa1a..fdf741fd58f 100644
--- a/llvm/lib/CodeGen/RegisterScavenging.cpp
+++ b/llvm/lib/CodeGen/RegisterScavenging.cpp
@@ -48,11 +48,6 @@ void RegScavenger::init(MachineBasicBlock &MBB) {
   assert((NumRegUnits == 0 || NumRegUnits == TRI->getNumRegUnits()) &&
          "Target changed?");
 
-  // It is not possible to use the register scavenger after late optimization
-  // passes that don't preserve accurate liveness information.
-  assert(MRI->tracksLiveness() &&
-         "Cannot use register scavenger with inaccurate liveness");
-
   // Self-initialize.
   if (!this->MBB) {
     NumRegUnits = TRI->getNumRegUnits();