[AutoDiff] NFC: garden differentiation transform. (swiftlang#32770)

Rename "emitters" to "cloners", for consistency:
- `JVPEmitter` -> `JVPCloner`
- `VJPEmitter` -> `VJPCloner`
- `PullbackEmitter` -> `PullbackCloner`

Improve `PullbackCloner` documentation.
- Document previously undocumented methods.
- Update outdated documentation.
  - For adjoint value accumulation helpers: rename "buffer access" occurrences to
    "address". Pullback generation no logner uses buffer accesses (`begin_apply`).

Author: dan-zheng

include/swift/SILOptimizer/Differentiation/JVPEmitter.h renamed to include/swift/SILOptimizer/Differentiation/JVPCloner.h

@@ -1,4 +1,4 @@
-//===--- JVPEmitter.h - JVP Generation in Differentiation -----*- C++ -*---===//
+//===--- JVPCloner.h - JVP function generation ----------------*- C++ -*---===//
 //
 // This source file is part of the Swift.org open source project
 //
@@ -15,8 +15,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_JVPEMITTER_H
-#define SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_JVPEMITTER_H
+#ifndef SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_JVPCLONER_H
+#define SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_JVPCLONER_H
 
 #include "swift/SILOptimizer/Differentiation/AdjointValue.h"
 #include "swift/SILOptimizer/Differentiation/DifferentiationInvoker.h"
@@ -40,8 +40,8 @@ namespace autodiff {
 
 class ADContext;
 
-class JVPEmitter final
-    : public TypeSubstCloner<JVPEmitter, SILOptFunctionBuilder> {
+class JVPCloner final
+    : public TypeSubstCloner<JVPCloner, SILOptFunctionBuilder> {
 private:
   /// The global context.
   ADContext &context;
@@ -368,9 +368,9 @@ class JVPEmitter final
   void prepareForDifferentialGeneration();
 
 public:
-  explicit JVPEmitter(ADContext &context, SILFunction *original,
-                      SILDifferentiabilityWitness *witness, SILFunction *jvp,
-                      DifferentiationInvoker invoker);
+  explicit JVPCloner(ADContext &context, SILFunction *original,
+                     SILDifferentiabilityWitness *witness, SILFunction *jvp,
+                     DifferentiationInvoker invoker);
 
   static SILFunction *
   createEmptyDifferential(ADContext &context,
@@ -411,4 +411,4 @@ class JVPEmitter final
 } // end namespace autodiff
 } // end namespace swift
 
-#endif // SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_VJPEMITTER_H
+#endif // SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_JVPCLONER_H

include/swift/SILOptimizer/Differentiation/PullbackEmitter.h renamed to include/swift/SILOptimizer/Differentiation/PullbackCloner.h

@@ -1,4 +1,4 @@
-//===--- VJPEmitter.h - VJP Generation in differentiation -----*- C++ -*---===//
+//===--- VJPCloner.h - VJP function generation ----------------*- C++ -*---===//
 //
 // This source file is part of the Swift.org open source project
 //
@@ -15,8 +15,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_VJPEMITTER_H
-#define SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_VJPEMITTER_H
+#ifndef SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_VJPCLONER_H
+#define SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_VJPCLONER_H
 
 #include "swift/SILOptimizer/Analysis/DifferentiableActivityAnalysis.h"
 #include "swift/SILOptimizer/Differentiation/DifferentiationInvoker.h"
@@ -35,11 +35,11 @@ class SILInstruction;
 namespace autodiff {
 
 class ADContext;
-class PullbackEmitter;
+class PullbackCloner;
 
-class VJPEmitter final
-    : public TypeSubstCloner<VJPEmitter, SILOptFunctionBuilder> {
-  friend class PullbackEmitter;
+class VJPCloner final
+    : public TypeSubstCloner<VJPCloner, SILOptFunctionBuilder> {
+  friend class PullbackCloner;
 
 private:
   /// The global context.
@@ -90,9 +90,9 @@ class VJPEmitter final
                   SILAutoDiffIndices indices, SILFunction *vjp);
 
 public:
-  explicit VJPEmitter(ADContext &context, SILFunction *original,
-                      SILDifferentiabilityWitness *witness, SILFunction *vjp,
-                      DifferentiationInvoker invoker);
+  explicit VJPCloner(ADContext &context, SILFunction *original,
+                     SILDifferentiabilityWitness *witness, SILFunction *vjp,
+                     DifferentiationInvoker invoker);
 
   SILFunction *createEmptyPullback();
 
@@ -170,4 +170,4 @@ class VJPEmitter final
 } // end namespace autodiff
 } // end namespace swift
 
-#endif // SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_VJPEMITTER_H
+#endif // SWIFT_SILOPTIMIZER_UTILS_DIFFERENTIATION_VJPCLONER_H

include/swift/SILOptimizer/Differentiation/VJPEmitter.h renamed to include/swift/SILOptimizer/Differentiation/VJPCloner.h

@@ -2,8 +2,8 @@ target_sources(swiftSILOptimizer PRIVATE
   ADContext.cpp
   Common.cpp
   DifferentiationInvoker.cpp
-  JVPEmitter.cpp
+  JVPCloner.cpp
   LinearMapInfo.cpp
-  PullbackEmitter.cpp
+  PullbackCloner.cpp
   Thunk.cpp
-  VJPEmitter.cpp)
+  VJPCloner.cpp)