[GISel] Add LookThroughInstrs for getIConstantVRegVal and getIConstantVRegSExtVal

The implementation of these methods uses getIConstantVRegValWithLookThrough
with LookThroughInstrs argument set to false. By adding the optional
argument to getIConstantVRegVal and getIConstantVRegSExtVal we can take
advantage of the already built look through functionality.

Author: michaelmaitland

llvm/lib/CodeGen/GlobalISel/Utils.cpp

@@ -290,9 +290,10 @@ void llvm::reportGISelFailure(MachineFunction &MF, const TargetPassConfig &TPC,
 }
 
 std::optional<APInt> llvm::getIConstantVRegVal(Register VReg,
-                                               const MachineRegisterInfo &MRI) {
-  std::optional<ValueAndVReg> ValAndVReg = getIConstantVRegValWithLookThrough(
-      VReg, MRI, /*LookThroughInstrs*/ false);
+                                               const MachineRegisterInfo &MRI,
+                                               bool LookThroughInstrs = false) {
+  std::optional<ValueAndVReg> ValAndVReg =
+      getIConstantVRegValWithLookThrough(VReg, MRI, LookThroughInstrs);
   assert((!ValAndVReg || ValAndVReg->VReg == VReg) &&
          "Value found while looking through instrs");
   if (!ValAndVReg)
@@ -301,7 +302,8 @@ std::optional<APInt> llvm::getIConstantVRegVal(Register VReg,
 }
 
 std::optional<int64_t>
-llvm::getIConstantVRegSExtVal(Register VReg, const MachineRegisterInfo &MRI) {
+llvm::getIConstantVRegSExtVal(Register VReg, const MachineRegisterInfo &MRI,
+                              bool LookThroughInstrs = false) {
   std::optional<APInt> Val = getIConstantVRegVal(VReg, MRI);
   if (Val && Val->getBitWidth() <= 64)
     return Val->getSExtValue();