AMDGPU: Fix adding duplicate implicit exec uses

[arsenm]

Summary

I'm not sure if this should be considered a bug in
copyImplicitOps or not, but implicit operands that are part
of the static instruction definition should not be copied.

[arsenm]

ping

[nhaehnle]

LGTM

[arsenm]

r280594

lib/Target/AMDGPU/SIShrinkInstructions.cpp

for (MachineOperand &Use : MI.implicit_operands()) {
     }
   }
 }
 
 static bool isKImmOperand(const SIInstrInfo *TII, const MachineOperand &Src) {
   return isInt<16>(Src.getImm()) && !TII->isInlineConstant(Src, 4);
 }
 
+/// Copy implicit register operands from specified instruction to this
+/// instruction that are not part of the instruction definition.
+static void copyExtraImplicitOps(MachineInstr &NewMI, MachineFunction &MF,
+                                 const MachineInstr &MI) {
+  for (unsigned i = MI.getDesc().getNumOperands() +
+         MI.getDesc().getNumImplicitUses() +
+         MI.getDesc().getNumImplicitDefs(), e = MI.getNumOperands();
+       i != e; ++i) {
+    const MachineOperand &MO = MI.getOperand(i);
+    if ((MO.isReg() && MO.isImplicit()) || MO.isRegMask())
+      NewMI.addOperand(MF, MO);
+  }
+}
+
 bool SIShrinkInstructions::runOnMachineFunction(MachineFunction &MF) {
   if (skipFunction(*MF.getFunction()))
     return false;
 
   MachineRegisterInfo &MRI = MF.getRegInfo();
   const SISubtarget &ST = MF.getSubtarget<SISubtarget>();
   const SIInstrInfo *TII = ST.getInstrInfo();
   const SIRegisterInfo &TRI = TII->getRegisterInfo();
for (I = MBB.begin(); I != MBB.end(); I = Next) {
           // during the initial BuildMI, so find it to preserve the flags.
           copyFlagsToImplicitVCC(*Inst32, *Src2);
         }
       }
 
       ++NumInstructionsShrunk;
 
       // Copy extra operands not present in the instruction definition.
-      Inst32->copyImplicitOps(MF, MI);
+      copyExtraImplicitOps(*Inst32, MF, MI);
 
       MI.eraseFromParent();
       foldImmediates(*Inst32, TII, MRI);
 
       DEBUG(dbgs() << "e32 MI = " << *Inst32 << '\n');
 
 
     }
   }
   return false;
 }