[llvm] r328509 - [Pipeliner] Pipeliner should mark physical registers as used

[Krzysztof Parzyszek via llvm-commits]

Author: kparzysz
Date: Mon Mar 26 08:53:23 2018
New Revision: 328509

URL: http://llvm.org/viewvc/llvm-project?rev=328509&view=rev
Log:
[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.


Modified:
    llvm/trunk/lib/CodeGen/MachinePipeliner.cpp

Modified: llvm/trunk/lib/CodeGen/MachinePipeliner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachinePipeliner.cpp?rev=328509&r1=328508&r2=328509&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachinePipeliner.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachinePipeliner.cpp Mon Mar 26 08:53:23 2018
@@ -2934,6 +2934,13 @@ void SwingSchedulerDAG::removeDeadInstru
         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 *
   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;
 }