[CoroutineAccessors] Add frame de/alloc functions.

To enable ABIs which store extra info in the frame, add two new slots to
the coroutine allocator function table.  For example, a frame could have
a header containing a context pointer at a negative offset from the
address returned from `swift_coro_alloc_frame`.  The frame deallocation
function would then know to deallocate more space correspondingly.

Author: nate-chandler

include/swift/ABI/Coro.h

@@ -61,11 +61,15 @@ struct CoroAllocator;
 using CoroAllocation = void *;
 using CoroAllocateFn = CoroAllocation (*)(CoroAllocator *, size_t);
 using CoroDealllocateFn = void (*)(CoroAllocator *, CoroAllocation);
+using CoroAllocateFrameFn = CoroAllocation (*)(CoroAllocator *, size_t);
+using CoroDealllocateFrameFn = void (*)(CoroAllocator *, CoroAllocation);
 
 struct CoroAllocator {
   CoroAllocatorFlags flags;
   CoroAllocateFn allocate;
   CoroDealllocateFn deallocate;
+  CoroAllocateFrameFn allocateFrame;
+  CoroDealllocateFrameFn deallocateFrame;
 
   /// Whether the allocator should deallocate memory on calls to
   /// swift_coro_dealloc.

include/swift/ABI/MetadataValues.h

@@ -1797,6 +1797,8 @@ namespace SpecialPointerAuthDiscriminators {
   /// Function pointers stored in the coro allocator struct.
   const uint16_t CoroAllocationFunction = 0x5f95;   // = 24469
   const uint16_t CoroDeallocationFunction = 0x9faf; // = 40879
+  const uint16_t CoroFrameAllocationFunction = 0xd251;   // = 53841
+  const uint16_t CoroFrameDeallocationFunction = 0x5ba8; // = 23464
 }
 
 /// The number of arguments that will be passed directly to a generic

include/swift/AST/IRGenOptions.h

@@ -257,6 +257,14 @@ struct PointerAuthOptions : clang::PointerAuthOptions {
 
   /// Stored in a coro allocator struct, the function used to deallocate memory.
   PointerAuthSchema CoroDeallocationFunction;
+
+  /// Stored in a coro allocator struct, the function used to allocate a callee
+  /// coroutine's fixed-size frame.
+  PointerAuthSchema CoroFrameAllocationFunction;
+
+  /// Stored in a coro allocator struct, the function used to deallocate a
+  /// callee coroutine's fixed-size frame.
+  PointerAuthSchema CoroFrameDeallocationFunction;
 };
 
 enum class JITDebugArtifact : unsigned {

lib/IRGen/GenCall.cpp

@@ -5178,10 +5178,12 @@ void irgen::emitYieldOnce2CoroutineEntry(IRGenFunction &IGF,
   IGF.setCoroutineAllocator(allocator);
   auto allocFn = IGF.IGM.getOpaquePtr(getCoroAllocFn(IGF.IGM));
   auto deallocFn = IGF.IGM.getOpaquePtr(getCoroDeallocFn(IGF.IGM));
+  auto allocFrameFn = IGF.IGM.getOpaquePtr(getCoroAllocFrameFn(IGF.IGM));
+  auto deallocFrameFn = IGF.IGM.getOpaquePtr(getCoroDeallocFrameFn(IGF.IGM));
   emitRetconCoroutineEntry(
       IGF, fnType, buffer, llvm::Intrinsic::coro_id_retcon_once_dynamic,
       Size(-1) /*dynamic-to-IRGen size*/, IGF.IGM.getCoroStaticFrameAlignment(),
-      {cfp, allocator}, allocFn, deallocFn, {});
+      {cfp, allocator}, allocFn, deallocFn, {allocFrameFn, deallocFrameFn});
 }
 void irgen::emitYieldOnce2CoroutineEntry(
     IRGenFunction &IGF, LinkEntity coroFunction, CanSILFunctionType fnType,
@@ -5267,17 +5269,19 @@ StackAddress irgen::emitAllocCoroStaticFrame(IRGenFunction &IGF,
   // TODO: Avoid swift_task_alloc (async) and malloc (yield_once) if the
   //       suspension doesn't span an apply of an async function or a yield
   //       respectively.
-  auto retval =
-      IGF.emitDynamicAlloca(IGF.IGM.Int8Ty, size, Alignment(MaximumAlignment),
-                            AllowsTaskAlloc, "caller-coro-frame");
+  auto retval = IGF.emitDynamicAlloca(
+      IGF.IGM.Int8Ty, size, Alignment(MaximumAlignment), AllowsTaskAlloc,
+      IsForCalleeCoroutineFrame_t(IGF.isCalleeAllocatedCoroutine()),
+      "callee-coro-frame");
   IGF.Builder.CreateLifetimeStart(retval.getAddress(),
                                   Size(-1) /*dynamic size*/);
   return retval;
 }
 void irgen::emitDeallocCoroStaticFrame(IRGenFunction &IGF, StackAddress frame) {
   IGF.Builder.CreateLifetimeEnd(frame.getAddress(), Size(-1) /*dynamic size*/);
   IGF.emitDeallocateDynamicAlloca(frame, /*allowTaskAlloc*/ true,
-                                  /*useTaskDeallocThrough*/ true);
+                                  /*useTaskDeallocThrough*/ true,
+                                  /*forCalleeCoroutineFrame*/ true);
 }
 
 llvm::Value *irgen::emitYield(IRGenFunction &IGF,