[llvm-commits] [llvm] r149144 - /llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp

[Benjamin Kramer]

On 27.01.2012, at 20:58, Lang Hames wrote:

> Author: lhames
> Date: Fri Jan 27 13:58:14 2012
> New Revision: 149144
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=149144&view=rev
> Log:
> Move some duplicate loops in the coalescer into their own function.
> 
> Modified:
>    llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
> 
> Modified: llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp?rev=149144&r1=149143&r2=149144&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp (original)
> +++ llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp Fri Jan 27 13:58:14 2012
> @@ -1421,6 +1421,42 @@
>   return true;
> }
> 
> +// Loop over the value numbers of the Dst interval and record the values that
> +// are defined by a copy from the Src interval.
> +static void FindValuesCopiedFrom(
> +                              LiveIntervals& lis,
> +                              const TargetRegisterInfo& tri,
> +                              CoalescerPair& CP, 
> +                              LiveInterval &Dst, LiveInterval &Src,
> +                              DenseMap<VNInfo*, VNInfo*>& DstValsDefinedFromSrc,
> +                              SmallVector<MachineInstr*, 8>& DupCopies) {
> +
> +  for (LiveInterval::vni_iterator i = Dst.vni_begin(), e = Dst.vni_end();
> +       i != e; ++i) {
> +    VNInfo *VNI = *i;
> +    if (VNI->isUnused() || !VNI->isDefByCopy())  // Src not defined by a copy?
> +      continue;
> +
> +    // Never join with a register that has EarlyClobber redefs.
> +    if (VNI->hasRedefByEC())
> +      return false;

GCC complains (correctly) about returning a value from a void function.

Also you copied this early exit from the other function, effectively changing behavior
because the caller doesn't return anymore when this condition is met.

- Ben

> +
> +    // Figure out the value # from the Src.
> +    LiveRange *lr = Src.getLiveRangeContaining(VNI->def.getPrevSlot());
> +    // The copy could be to an aliased physreg.
> +    if (!lr) continue;
> +
> +    // DstReg is known to be a register in the Dst interval.  If the src is
> +    // from the Src interval, we can use its value #.
> +    MachineInstr *MI = VNI->getCopy();
> +    if (!CP.isCoalescable(MI) &&
> +        !RegistersDefinedFromSameValue(lis, tri, CP, VNI, lr, DupCopies))
> +      continue;
> +
> +    DstValsDefinedFromSrc[VNI] = lr->valno;
> +  }
> +}                            
> +
> /// JoinIntervals - Attempt to join these two intervals.  On failure, this
> /// returns false.
> bool RegisterCoalescer::JoinIntervals(CoalescerPair &CP) {
> @@ -1506,59 +1542,9 @@
>   LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg());
>   DEBUG({ dbgs() << "\t\tLHS = "; LHS.print(dbgs(), TRI); dbgs() << "\n"; });
> 
> -  // Loop over the value numbers of the LHS, seeing if any are defined from
> -  // the RHS.
> -  for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
> -       i != e; ++i) {
> -    VNInfo *VNI = *i;
> -    if (VNI->isUnused() || !VNI->isDefByCopy())  // Src not defined by a copy?
> -      continue;
> -
> -    // Never join with a register that has EarlyClobber redefs.
> -    if (VNI->hasRedefByEC())
> -      return false;
> -
> -    // Figure out the value # from the RHS.
> -    LiveRange *lr = RHS.getLiveRangeContaining(VNI->def.getPrevSlot());
> -    // The copy could be to an aliased physreg.
> -    if (!lr) continue;
> -
> -    // DstReg is known to be a register in the LHS interval.  If the src is
> -    // from the RHS interval, we can use its value #.
> -    MachineInstr *MI = VNI->getCopy();
> -    if (!CP.isCoalescable(MI) &&
> -        !RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
> -      continue;
> -
> -    LHSValsDefinedFromRHS[VNI] = lr->valno;
> -  }
> -
> -  // Loop over the value numbers of the RHS, seeing if any are defined from
> -  // the LHS.
> -  for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
> -       i != e; ++i) {
> -    VNInfo *VNI = *i;
> -    if (VNI->isUnused() || !VNI->isDefByCopy())  // Src not defined by a copy?
> -      continue;
> -
> -    // Never join with a register that has EarlyClobber redefs.
> -    if (VNI->hasRedefByEC())
> -      return false;
> -
> -    // Figure out the value # from the LHS.
> -    LiveRange *lr = LHS.getLiveRangeContaining(VNI->def.getPrevSlot());
> -    // The copy could be to an aliased physreg.
> -    if (!lr) continue;
> -
> -    // DstReg is known to be a register in the RHS interval.  If the src is
> -    // from the LHS interval, we can use its value #.
> -    MachineInstr *MI = VNI->getCopy();
> -    if (!CP.isCoalescable(MI) &&
> -        !RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
> -        continue;
> -
> -    RHSValsDefinedFromLHS[VNI] = lr->valno;
> -  }
> +  // Build a map of LHS values defined by copies from RHS and vice-versa.
> +  FindValuesCopiedFrom(*LIS, *TRI, CP, LHS, RHS, LHSValsDefinedFromRHS, DupCopies);
> +  FindValuesCopiedFrom(*LIS, *TRI, CP, RHS, LHS, RHSValsDefinedFromLHS, DupCopies);
> 
>   LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
>   RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
> 
> 
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