ARM scheduling fix: don't guess at implicit operand latency.

This is a minor drive-by fix with no robust way to unit test.
As an example see neon-div.ll:
SU(16):   %Q8<def> = VMOVLsv4i32 %D17, pred:14, pred:%noreg, %Q8<imp-use,kill>
 val SU(1): Latency=2 Reg=%Q8
...should be latency=1

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158960 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 5 deletions

diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index cceb05e461..e30f6d200c 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -2746,11 +2746,12 @@ ARMBaseInstrInfo::getOperandLatency(const InstrItineraryData *ItinData,
     unsigned NewUseIdx;
     const MachineInstr *NewUseMI = getBundledUseMI(&getRegisterInfo(), UseMI,
                                                    Reg, NewUseIdx, UseAdj);
-    if (NewUseMI) {
-      UseMI = NewUseMI;
-      UseIdx = NewUseIdx;
-      UseMCID = &UseMI->getDesc();
-    }
+    if (!NewUseMI)
+      return -1;
+
+    UseMI = NewUseMI;
+    UseIdx = NewUseIdx;
+    UseMCID = &UseMI->getDesc();
   }
 
   if (Reg == ARM::CPSR) {
@@ -2778,6 +2779,9 @@ ARMBaseInstrInfo::getOperandLatency(const InstrItineraryData *ItinData,
     return Latency;
   }
 
+  if (DefMO.isImplicit() || UseMI->getOperand(UseIdx).isImplicit())
+    return -1;
+
   unsigned DefAlign = DefMI->hasOneMemOperand()
     ? (*DefMI->memoperands_begin())->getAlignment() : 0;
   unsigned UseAlign = UseMI->hasOneMemOperand()