[Pipeliner] Pipeliner should mark physical registers as used

The software pipeliner attempts to delete dead instructions after
generating the pipelined loop. The code looks for uses of each
instruction. Physical registers should be treated differently because
the use chains do not exist. The code that checks for dead
instructions should assume that definitions of physical registers
are used if the operand doesn't contain the dead flag.

Patch by Brendon Cahoon.

llvm-svn: 328509

diff --git a/llvm/lib/CodeGen/MachinePipeliner.cpp b/llvm/lib/CodeGen/MachinePipeliner.cpp
index 17c2564..527f1e4 100644 (file)
--- a/llvm/lib/CodeGen/MachinePipeliner.cpp
+++ b/llvm/lib/CodeGen/MachinePipeliner.cpp
@@ -2934,6 +2934,13 @@ void SwingSchedulerDAG::removeDeadInstructions(MachineBasicBlock *KernelBB,
         if (!MOI->isReg() || !MOI->isDef())
           continue;
         unsigned reg = MOI->getReg();
+        // Assume physical registers are used, unless they are marked dead.
+        if (TargetRegisterInfo::isPhysicalRegister(reg)) {
+          used = !MOI->isDead();
+          if (used)
+            break;
+          continue;
+        }
         unsigned realUses = 0;
         for (MachineRegisterInfo::use_iterator UI = MRI.use_begin(reg),
                                                EI = MRI.use_end();
@@ -3650,7 +3657,7 @@ static SUnit *multipleIterations(SUnit *SU, SwingSchedulerDAG *DAG) {
   for (auto &P : SU->Preds)
     if (DAG->isBackedge(SU, P) && P.getSUnit()->getInstr()->isPHI())
       for (auto &S : P.getSUnit()->Succs)
-        if (S.getKind() == SDep::Order && S.getSUnit()->getInstr()->isPHI())
+        if (S.getKind() == SDep::Data && S.getSUnit()->getInstr()->isPHI())
           return P.getSUnit();
   return nullptr;
 }