[sil] Change usages of SILArguments in SILArgument.h to use exhaustive switches over ArgumentKinds.

This will ensure we get uncovered switch warnings when we add new argument
kinds, easing adding of such arguments without introducing errors.

Author: gottesmm

include/swift/SIL/SILArgument.h

@@ -334,50 +334,73 @@ class SILFunctionArgument : public SILArgument {
 //===----------------------------------------------------------------------===//
 
 inline bool SILArgument::isPhiArgument() const {
-  if (auto *phiArg = dyn_cast<SILPhiArgument>(this))
-    return phiArg->isPhiArgument();
-
-  return false;
+  switch (getKind()) {
+  case SILArgumentKind::SILPhiArgument:
+    return cast<SILPhiArgument>(this)->isPhiArgument();
+  case SILArgumentKind::SILFunctionArgument:
+    return false;
+  }
+  llvm_unreachable("Covered switch is not covered?!");
 }
 
 inline SILValue
 SILArgument::getIncomingPhiValue(SILBasicBlock *predBlock) const {
-  if (isa<SILFunctionArgument>(this))
+  switch (getKind()) {
+  case SILArgumentKind::SILPhiArgument:
+    return cast<SILPhiArgument>(this)->getIncomingPhiValue(predBlock);
+  case SILArgumentKind::SILFunctionArgument:
     return SILValue();
-  return cast<SILPhiArgument>(this)->getIncomingPhiValue(predBlock);
+  }
+  llvm_unreachable("Covered switch is not covered?!");
 }
 
 inline bool SILArgument::getIncomingPhiValues(
     SmallVectorImpl<SILValue> &returnedPhiValues) const {
-  if (isa<SILFunctionArgument>(this))
+  switch (getKind()) {
+  case SILArgumentKind::SILPhiArgument:
+    return cast<SILPhiArgument>(this)->getIncomingPhiValues(returnedPhiValues);
+  case SILArgumentKind::SILFunctionArgument:
     return false;
-  return cast<SILPhiArgument>(this)->getIncomingPhiValues(returnedPhiValues);
+  }
+  llvm_unreachable("Covered switch is not covered?!");
 }
 
 inline bool SILArgument::getIncomingPhiValues(
     SmallVectorImpl<std::pair<SILBasicBlock *, SILValue>>
         &returnedPredAndPhiValuePairs) const {
-  if (isa<SILFunctionArgument>(this))
+  switch (getKind()) {
+  case SILArgumentKind::SILPhiArgument:
+    return cast<SILPhiArgument>(this)->getIncomingPhiValues(
+        returnedPredAndPhiValuePairs);
+  case SILArgumentKind::SILFunctionArgument:
     return false;
-  return cast<SILPhiArgument>(this)->getIncomingPhiValues(
-      returnedPredAndPhiValuePairs);
+  }
+  llvm_unreachable("Covered switch is not covered?!");
 }
 
 inline bool SILArgument::getSingleTerminatorOperands(
     SmallVectorImpl<SILValue> &returnedSingleTermOperands) const {
-  if (isa<SILFunctionArgument>(this))
+  switch (getKind()) {
+  case SILArgumentKind::SILPhiArgument:
+    return cast<SILPhiArgument>(this)->getSingleTerminatorOperands(
+        returnedSingleTermOperands);
+  case SILArgumentKind::SILFunctionArgument:
     return false;
-  return cast<SILPhiArgument>(this)->getSingleTerminatorOperands(
-      returnedSingleTermOperands);
+  }
+  llvm_unreachable("Covered switch is not covered?!");
 }
 
 inline bool SILArgument::getSingleTerminatorOperands(
     SmallVectorImpl<std::pair<SILBasicBlock *, SILValue>>
         &returnedSingleTermOperands) const {
-  if (isa<SILFunctionArgument>(this))
+  switch (getKind()) {
+  case SILArgumentKind::SILPhiArgument:
+    return cast<SILPhiArgument>(this)->getSingleTerminatorOperands(
+        returnedSingleTermOperands);
+  case SILArgumentKind::SILFunctionArgument:
     return false;
-  return cast<SILPhiArgument>(this)->getSingleTerminatorOperands(
-      returnedSingleTermOperands);
+  }
+  llvm_unreachable("Covered switch is not covered?!");
 }
 
 } // end swift namespace