[Target] Prevent copying in loop variables (NFC)

/data/llvm-project/llvm/lib/Target/Lanai/LanaiISelLowering.cpp:715:19: error: loop variable '[Reg, N]' creates a copy from type 'std::pair<unsigned int, llvm::SDValue> const' [-Werror,-Wrange-loop-construct]
  for (const auto [Reg, N] : RegsToPass) {
                  ^
/data/llvm-project/llvm/lib/Target/Lanai/LanaiISelLowering.cpp:715:8: note: use reference type 'std::pair<unsigned int, llvm::SDValue> const &' to prevent copying
  for (const auto [Reg, N] : RegsToPass) {
       ^~~~~~~~~~~~~~~~~~~~~
                  &
/data/llvm-project/llvm/lib/Target/Lanai/LanaiISelLowering.cpp:747:19: error: loop variable '[Reg, N]' creates a copy from type 'std::pair<unsigned int, llvm::SDValue> const' [-Werror,-Wrange-loop-construct]
  for (const auto [Reg, N] : RegsToPass)
                  ^
/data/llvm-project/llvm/lib/Target/Lanai/LanaiISelLowering.cpp:747:8: note: use reference type 'std::pair<unsigned int, llvm::SDValue> const &' to prevent copying
  for (const auto [Reg, N] : RegsToPass)
       ^~~~~~~~~~~~~~~~~~~~~
                  &
2 errors generated.

Author: DamonFool

llvm/lib/Target/Lanai/LanaiISelLowering.cpp

@@ -712,7 +712,7 @@ SDValue LanaiTargetLowering::LowerCCCCallTo(
   // Build a sequence of copy-to-reg nodes chained together with token chain and
   // flag operands which copy the outgoing args into registers.  The InGlue in
   // necessary since all emitted instructions must be stuck together.
-  for (const auto [Reg, N] : RegsToPass) {
+  for (const auto &[Reg, N] : RegsToPass) {
     Chain = DAG.getCopyToReg(Chain, DL, Reg, N, InGlue);
     InGlue = Chain.getValue(1);
   }
@@ -744,7 +744,7 @@ SDValue LanaiTargetLowering::LowerCCCCallTo(
 
   // Add argument registers to the end of the list so that they are
   // known live into the call.
-  for (const auto [Reg, N] : RegsToPass)
+  for (const auto &[Reg, N] : RegsToPass)
     Ops.push_back(DAG.getRegister(Reg, N.getValueType()));
 
   if (InGlue.getNode())

llvm/lib/Target/MSP430/MSP430ISelLowering.cpp

@@ -768,7 +768,7 @@ SDValue MSP430TargetLowering::LowerCCCCallTo(
   // flag operands which copy the outgoing args into registers.  The InGlue in
   // necessary since all emitted instructions must be stuck together.
   SDValue InGlue;
-  for (const auto [Reg, N] : RegsToPass) {
+  for (const auto &[Reg, N] : RegsToPass) {
     Chain = DAG.getCopyToReg(Chain, dl, Reg, N, InGlue);
     InGlue = Chain.getValue(1);
   }
@@ -789,7 +789,7 @@ SDValue MSP430TargetLowering::LowerCCCCallTo(
 
   // Add argument registers to the end of the list so that they are
   // known live into the call.
-  for (const auto [Reg, N] : RegsToPass)
+  for (const auto &[Reg, N] : RegsToPass)
     Ops.push_back(DAG.getRegister(Reg, N.getValueType()));
 
   if (InGlue.getNode())

llvm/lib/Target/VE/VEISelLowering.cpp

@@ -738,15 +738,15 @@ SDValue VETargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   // necessary since all emitted instructions must be stuck together in order
   // to pass the live physical registers.
   SDValue InGlue;
-  for (const auto [Reg, N] : RegsToPass) {
+  for (const auto &[Reg, N] : RegsToPass) {
     Chain = DAG.getCopyToReg(Chain, DL, Reg, N, InGlue);
     InGlue = Chain.getValue(1);
   }
 
   // Build the operands for the call instruction itself.
   SmallVector<SDValue, 8> Ops;
   Ops.push_back(Chain);
-  for (const auto [Reg, N] : RegsToPass)
+  for (const auto &[Reg, N] : RegsToPass)
     Ops.push_back(DAG.getRegister(Reg, N.getValueType()));
 
   // Add a register mask operand representing the call-preserved registers.

llvm/lib/Target/XCore/XCoreISelLowering.cpp

@@ -1064,7 +1064,7 @@ SDValue XCoreTargetLowering::LowerCCCCallTo(
   // The InGlue in necessary since all emitted instructions must be
   // stuck together.
   SDValue InGlue;
-  for (const auto [Reg, N] : RegsToPass) {
+  for (const auto &[Reg, N] : RegsToPass) {
     Chain = DAG.getCopyToReg(Chain, dl, Reg, N, InGlue);
     InGlue = Chain.getValue(1);
   }
@@ -1088,7 +1088,7 @@ SDValue XCoreTargetLowering::LowerCCCCallTo(
 
   // Add argument registers to the end of the list so that they are
   // known live into the call.
-  for (const auto [Reg, N] : RegsToPass)
+  for (const auto &[Reg, N] : RegsToPass)
     Ops.push_back(DAG.getRegister(Reg, N.getValueType()));
 
   if (InGlue.getNode())