[GISel]: Avoid zero length array when building Instrs that don't have

uses.

Also splitting the buildSources part allows more overloads such as
adding MachineOperands directly in the arguments for buildInstr.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309163 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h b/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
index 85e6fef1f3c2623c1c30065c595e0cfac56286bd..9b598491c0b75154dac32e530eb680084e552b45 100644 (file)
--- a/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
+++ b/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
@@ -70,12 +70,20 @@ class MachineIRBuilder {
     return getMF().getRegInfo().createVirtualRegister(RC);
   }
 
-  unsigned getRegFromArg(unsigned Reg) { return Reg; }
+  void addUseFromArg(MachineInstrBuilder &MIB, unsigned Reg) {
+    MIB.addUse(Reg);
+  }
 
-  unsigned getRegFromArg(const MachineInstrBuilder &MIB) {
-    return MIB->getOperand(0).getReg();
+  void addUseFromArg(MachineInstrBuilder &MIB, const MachineInstrBuilder &UseMIB) {
+    MIB.addUse(UseMIB->getOperand(0).getReg());
   }
 
+  void addUsesFromArgs(MachineInstrBuilder &MIB) { }
+  template<typename UseArgTy, typename ... UseArgsTy>
+  void addUsesFromArgs(MachineInstrBuilder &MIB, UseArgTy &&Arg1, UseArgsTy &&... Args) {
+    addUseFromArg(MIB, Arg1);
+    addUsesFromArgs(std::forward<UseArgsTy>(Args)...);
+  }
 public:
   /// Getter for the function we currently build.
   MachineFunction &getMF() {
@@ -146,9 +154,7 @@ public:
   MachineInstrBuilder buildInstr(unsigned Opc, DstTy &&Ty,
                                  UseArgsTy &&... Args) {
     auto MIB = buildInstr(Opc).addDef(getDestFromArg(Ty));
-    unsigned It[] = {(getRegFromArg(Args))...};
-    for (const auto &i : It)
-      MIB.addUse(i);
+    addUsesFromArgs(MIB, std::forward<UseArgsTy>(Args)...);
     return MIB;
   }