[Coroutines] Make sure that async coroutine context size is a multiple of the alignment requirement

This simplifies the code the allocator has to executed

Differential Revision: https://reviews.llvm.org/D91471

Author: aschwaighofer

llvm/lib/Transforms/Coroutines/CoroFrame.cpp

@@ -791,8 +791,11 @@ static StructType *buildFrameType(Function &F, coro::Shape &Shape,
   case coro::ABI::Async: {
     Shape.AsyncLowering.FrameOffset =
         alignTo(Shape.AsyncLowering.ContextHeaderSize, Shape.FrameAlign);
+    // Also make the final context size a multiple of the context alignment to
+    // make allocation easier for allocators.
     Shape.AsyncLowering.ContextSize =
-        Shape.AsyncLowering.FrameOffset + Shape.FrameSize;
+        alignTo(Shape.AsyncLowering.FrameOffset + Shape.FrameSize,
+                Shape.AsyncLowering.getContextAlignment());
     if (Shape.AsyncLowering.getContextAlignment() < Shape.FrameAlign) {
       report_fatal_error(
           "The alignment requirment of frame variables cannot be higher than "

llvm/test/Transforms/Coroutines/coro-async.ll

@@ -99,8 +99,8 @@ entry:
 }
 
 ; Make sure we update the async function pointer
-; CHECK: @my_async_function_fp = constant <{ i32, i32 }> <{ {{.*}}, i32 168 }
-; CHECK: @my_async_function2_fp = constant <{ i32, i32 }> <{ {{.*}}, i32 168 }
+; CHECK: @my_async_function_fp = constant <{ i32, i32 }> <{ {{.*}}, i32 176 }
+; CHECK: @my_async_function2_fp = constant <{ i32, i32 }> <{ {{.*}}, i32 176 }
 
 ; CHECK-LABEL: define swiftcc void @my_async_function(i8* %async.ctxt, %async.task* %task, %async.actor* %actor) {
 ; CHECK: entry: