Teach if-converter to be more careful with predicating instructions that would

take multiple cycles to decode.
For the current if-converter clients (actually only ARM), the instructions that
are predicated on false are not nops. They would still take machine cycles to
decode. Micro-coded instructions such as LDM / STM can potentially take multiple
cycles to decode. If-converter should take treat them as non-micro-coded
simple instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113570 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 15 deletions

diff --git a/lib/CodeGen/ScheduleDAGInstrs.cpp b/lib/CodeGen/ScheduleDAGInstrs.cpp
index ea93dd5c66..da0b0562e1 100644
--- a/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -32,9 +32,9 @@ using namespace llvm;
 ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
                                      const MachineLoopInfo &mli,
                                      const MachineDominatorTree &mdt)
-  : ScheduleDAG(mf), MLI(mli), MDT(mdt), Defs(TRI->getNumRegs()),
-    Uses(TRI->getNumRegs()), LoopRegs(MLI, MDT) {
-  MFI = mf.getFrameInfo();
+  : ScheduleDAG(mf), MLI(mli), MDT(mdt), MFI(mf.getFrameInfo()),
+    InstrItins(mf.getTarget().getInstrItineraryData()),
+    Defs(TRI->getNumRegs()), Uses(TRI->getNumRegs()), LoopRegs(MLI, MDT) {
   DbgValueVec.clear();
 }
 
@@ -498,23 +498,22 @@ void ScheduleDAGInstrs::FinishBlock() {
 }
 
 void ScheduleDAGInstrs::ComputeLatency(SUnit *SU) {
-  const InstrItineraryData &InstrItins = TM.getInstrItineraryData();
-
   // Compute the latency for the node.
-  SU->Latency =
-    InstrItins.getStageLatency(SU->getInstr()->getDesc().getSchedClass());
+  if (!InstrItins || InstrItins->isEmpty()) {
+    SU->Latency = 1;
 
-  // Simplistic target-independent heuristic: assume that loads take
-  // extra time.
-  if (InstrItins.isEmpty())
+    // Simplistic target-independent heuristic: assume that loads take
+    // extra time.
     if (SU->getInstr()->getDesc().mayLoad())
       SU->Latency += 2;
+  } else
+    SU->Latency =
+      InstrItins->getStageLatency(SU->getInstr()->getDesc().getSchedClass());
 }
 
 void ScheduleDAGInstrs::ComputeOperandLatency(SUnit *Def, SUnit *Use, 
                                               SDep& dep) const {
-  const InstrItineraryData &InstrItins = TM.getInstrItineraryData();
-  if (InstrItins.isEmpty())
+  if (!InstrItins || InstrItins->isEmpty())
     return;
   
   // For a data dependency with a known register...
@@ -528,8 +527,8 @@ void ScheduleDAGInstrs::ComputeOperandLatency(SUnit *Def, SUnit *Use,
   MachineInstr *DefMI = Def->getInstr();
   int DefIdx = DefMI->findRegisterDefOperandIdx(Reg);
   if (DefIdx != -1) {
-    int DefCycle = InstrItins.getOperandCycle(DefMI->getDesc().getSchedClass(),
-                                              DefIdx);
+    int DefCycle = InstrItins->getOperandCycle(DefMI->getDesc().getSchedClass(),
+                                               DefIdx);
     if (DefCycle >= 0) {
       MachineInstr *UseMI = Use->getInstr();
       const unsigned UseClass = UseMI->getDesc().getSchedClass();
@@ -544,7 +543,7 @@ void ScheduleDAGInstrs::ComputeOperandLatency(SUnit *Def, SUnit *Use,
         if (MOReg != Reg)
           continue;
 
-        int UseCycle = InstrItins.getOperandCycle(UseClass, i);
+        int UseCycle = InstrItins->getOperandCycle(UseClass, i);
         if (UseCycle >= 0)
           Latency = std::max(Latency, DefCycle - UseCycle + 1);
       }