[SIL] Function args may have lifetime annotations.

By default, whether a function argument's lifetime is determined by its
type.  To allow that behavior to be overridden on an
argument-by-argument basis, the argument may have its own lifetime.

Author: nate-chandler

include/swift/SIL/SILArgument.h

@@ -13,10 +13,12 @@
 #ifndef SWIFT_SIL_SILARGUMENT_H
 #define SWIFT_SIL_SILARGUMENT_H
 
+#include "swift/AST/LifetimeAnnotation.h"
 #include "swift/Basic/Compiler.h"
+#include "swift/SIL/Lifetime.h"
 #include "swift/SIL/SILArgumentConvention.h"
-#include "swift/SIL/SILValue.h"
 #include "swift/SIL/SILFunctionConventions.h"
+#include "swift/SIL/SILValue.h"
 
 namespace swift {
 
@@ -327,14 +329,17 @@ class SILFunctionArgument : public SILArgument {
   friend class SILBasicBlock;
 
   bool noImplicitCopy = false;
+  LifetimeAnnotation lifetimeAnnotation = LifetimeAnnotation::None;
 
-  SILFunctionArgument(SILBasicBlock *parentBlock, SILType type,
-                      ValueOwnershipKind ownershipKind,
-                      const ValueDecl *decl = nullptr,
-                      bool isNoImplicitCopy = false)
+  SILFunctionArgument(
+      SILBasicBlock *parentBlock, SILType type,
+      ValueOwnershipKind ownershipKind, const ValueDecl *decl = nullptr,
+      bool isNoImplicitCopy = false,
+      LifetimeAnnotation lifetimeAnnotation = LifetimeAnnotation::None)
       : SILArgument(ValueKind::SILFunctionArgument, parentBlock, type,
                     ownershipKind, decl),
-        noImplicitCopy(isNoImplicitCopy) {}
+        noImplicitCopy(isNoImplicitCopy),
+        lifetimeAnnotation(lifetimeAnnotation) {}
   // A special constructor, only intended for use in
   // SILBasicBlock::replaceFunctionArg.
   explicit SILFunctionArgument(SILType type, ValueOwnershipKind ownershipKind,
@@ -347,6 +352,20 @@ class SILFunctionArgument : public SILArgument {
 
   void setNoImplicitCopy(bool newValue) { noImplicitCopy = newValue; }
 
+  LifetimeAnnotation getLifetimeAnnotation() const {
+    return lifetimeAnnotation;
+  }
+
+  void setLifetimeAnnotation(LifetimeAnnotation newValue) {
+    lifetimeAnnotation = newValue;
+  }
+
+  Lifetime getLifetime() const {
+    return getType()
+        .getLifetime(*getFunction())
+        .getLifetimeForAnnotatedValue(getLifetimeAnnotation());
+  }
+
   bool isIndirectResult() const;
 
   SILArgumentConvention getArgumentConvention() const;