LivePhysRegs: Automatically determine presence of pristine regs.

Remove the AddPristinesAndCSRs parameters from
addLiveIns()/addLiveOuts().

We need to respect pristine registers after prologue epilogue insertion,
Seeing that we got this wrong in at least two commits already, we should
rather pay the small price to query MachineFrameInfo for it.

There are three cases that did not set AddPristineAndCSRs to true even
after register allocation:
- ExecutionDepsFix: live-out registers are used as a hint that the
  register is used soon. This is not true for pristine registers so
  use the new addLiveOutsNoPristines() to maintain this behaviour.
- SystemZShortenInst: Not setting AddPristineAndCSRs to true looks like
  a bug, should do the right thing automatically now.
- StackMapLivenessAnalysis: Not adding pristine registers looks like a
  bug to me. Added a FIXME comment but maintain the current behaviour
  as a change may need to get coordinated with GC runtimes.

llvm-svn: 268336

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/ExecutionDepsFix.cpp b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
index 70945832942..12ea9e3844b 100644
--- a/llvm/lib/CodeGen/ExecutionDepsFix.cpp
+++ b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
@@ -558,7 +558,9 @@ void ExeDepsFix::processUndefReads(MachineBasicBlock *MBB) {
 
   // Collect this block's live out register units.
   LiveRegSet.init(TRI);
-  LiveRegSet.addLiveOuts(MBB);
+  // We do not need to care about pristine registers as they are just preserved
+  // but not actually used in the function.
+  LiveRegSet.addLiveOutsNoPristines(MBB);
 
   MachineInstr *UndefMI = UndefReads.back().first;
   unsigned OpIdx = UndefReads.back().second;