Revert "CodeGen: Disable isCopyInstrImpl if there are implicit operands"

This reverts commit bc7d88f.

This is broken with 414ff81 reverted.

Author: arsenm

llvm/include/llvm/CodeGen/TargetInstrInfo.h

@@ -1036,29 +1036,10 @@ class TargetInstrInfo : public MCInstrInfo {
   /// For COPY-instruction the method naturally returns destination and source
   /// registers as machine operands, for all other instructions the method calls
   /// target-dependent implementation.
-  std::optional<DestSourcePair>
-  isCopyInstr(const MachineInstr &MI,
-              bool ForbidImplicitOperands = true) const {
+  std::optional<DestSourcePair> isCopyInstr(const MachineInstr &MI) const {
     if (MI.isCopy()) {
-      // TODO: Should validate implicit operands here?
       return DestSourcePair{MI.getOperand(0), MI.getOperand(1)};
     }
-
-    // TODO: This is a conservative hack to ensure correctness when extra
-    // operands are added for special liveness tracking, while also not changing
-    // debug info. In particular SUBREG_TO_REG may introduce an implicit-def of
-    // a super register after coalescing. This may manifest as a copy-like
-    // instruction with an undef subregister def, and a full register
-    // implicit-def appended to the operand list.
-
-    // Really, implementations of this should be considering extra implicit
-    // operands. A more sophisticated implementation would recognize an
-    // implicit-def of the full register, and report that as the
-    // destination. This should be removed when all targets are validated for
-    // correct SUBREG_TO_REG liveness handling.
-    if (ForbidImplicitOperands && MI.getNumImplicitOperands() != 0)
-      return std::nullopt;
-
     return isCopyInstrImpl(MI);
   }
 

llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp

@@ -2116,7 +2116,7 @@ bool InstrRefBasedLDV::transferSpillOrRestoreInst(MachineInstr &MI) {
 }
 
 bool InstrRefBasedLDV::transferRegisterCopy(MachineInstr &MI) {
-  auto DestSrc = TII->isCopyInstr(MI, false);
+  auto DestSrc = TII->isCopyInstr(MI);
   if (!DestSrc)
     return false;
 

llvm/lib/CodeGen/LiveDebugValues/VarLocBasedImpl.cpp

@@ -1364,7 +1364,7 @@ void VarLocBasedLDV::removeEntryValue(const MachineInstr &MI,
     // TODO: Try to keep tracking of an entry value if we encounter a propagated
     // DBG_VALUE describing the copy of the entry value. (Propagated entry value
     // does not indicate the parameter modification.)
-    auto DestSrc = TII->isCopyInstr(*TransferInst, false);
+    auto DestSrc = TII->isCopyInstr(*TransferInst);
     if (DestSrc) {
       const MachineOperand *SrcRegOp, *DestRegOp;
       SrcRegOp = DestSrc->Source;
@@ -1840,7 +1840,7 @@ void VarLocBasedLDV::transferRegisterCopy(MachineInstr &MI,
                                            OpenRangesSet &OpenRanges,
                                            VarLocMap &VarLocIDs,
                                            TransferMap &Transfers) {
-  auto DestSrc = TII->isCopyInstr(MI, false);
+  auto DestSrc = TII->isCopyInstr(MI);
   if (!DestSrc)
     return;
 

llvm/lib/Target/AArch64/AArch64InstrInfo.cpp

@@ -9176,7 +9176,7 @@ static std::optional<ParamLoadedValue>
 describeORRLoadedValue(const MachineInstr &MI, Register DescribedReg,
                        const TargetInstrInfo *TII,
                        const TargetRegisterInfo *TRI) {
-  auto DestSrc = TII->isCopyInstr(MI, false);
+  auto DestSrc = TII->isCopyInstr(MI);
   if (!DestSrc)
     return std::nullopt;