SIL: let TypeValueInst.value return an optional Int

and don't require the client to check if it's an integer type.
Also, implement `var value` natively and without bridging.

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyMisc.swift

@@ -15,7 +15,7 @@ import SIL
 extension TypeValueInst: OnoneSimplifiable, SILCombineSimplifiable {
   func simplify(_ context: SimplifyContext) {
     // If our parameter is not known statically, then bail.
-    guard paramType.isInteger else {
+    guard let value = value else {
       return
     }
 

SwiftCompilerSources/Sources/SIL/Instruction.swift

@@ -862,8 +862,12 @@ final public class TypeValueInst: SingleValueInstruction, UnaryInstruction {
     CanonicalType(bridged: bridged.TypeValueInst_getParamType())
   }
 
-  public var value: Int {
-    bridged.TypeValueInst_getValue()
+  /// Returns the value of the Integer type is known and fits into an `Int`.
+  public var value: Int? {
+    if paramType.isInteger {
+      return paramType.valueOfInteger
+    }
+    return nil
   }
 }
 

include/swift/SIL/SILBridging.h

@@ -857,7 +857,6 @@ struct BridgedInstruction {
   BRIDGED_INLINE SwiftInt FullApplySite_numIndirectResultArguments() const;
   BRIDGED_INLINE bool ConvertFunctionInst_withoutActuallyEscaping() const;
   SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedCanType TypeValueInst_getParamType() const;
-  BRIDGED_INLINE SwiftInt TypeValueInst_getValue() const;
 
   // =========================================================================//
   //                   VarDeclInst and DebugVariableInst

include/swift/SIL/SILBridgingImpl.h

@@ -1659,19 +1659,6 @@ BridgedCanType BridgedInstruction::TypeValueInst_getParamType() const {
   return getAs<swift::TypeValueInst>()->getParamType();
 }
 
-SwiftInt BridgedInstruction::TypeValueInst_getValue() const {
-  auto tvi = getAs<swift::TypeValueInst>();
-
-  // Assume we've already checked that the parameter type is an IntegerType.
-  auto integer = tvi->getParamType()->castTo<swift::IntegerType>();
-
-  if (integer->isNegative()) {
-    return integer->getValue().getSExtValue();
-  } else {
-    return integer->getValue().getZExtValue();
-  }
-}
-
 //===----------------------------------------------------------------------===//
 //                     VarDeclInst and DebugVariableInst
 //===----------------------------------------------------------------------===//