[Coroutines] Remove assert about a promise being present (#156007)

This commit removes an assert in the generation of debug info for a
coroutine frame. This assert checked if a promise alloca is present,
even though it's not used. While this might always be the case when the
coroutine was produced by clang++, this doesn't hold in the general
case.

Note: We generate coroutine intrinsics from downstream passes. In our
case, there is no guarantee that a coroutine has any promise, but they
can originate from some non-coro C++ code.

Author: Dinistro

llvm/lib/Transforms/Coroutines/CoroFrame.cpp

@@ -700,9 +700,6 @@ static void buildFrameDebugInfo(Function &F, coro::Shape &Shape,
 
   DIBuilder DBuilder(*F.getParent(), /*AllowUnresolved*/ false);
 
-  assert(Shape.getPromiseAlloca() &&
-         "Coroutine with switch ABI should own Promise alloca");
-
   DIFile *DFile = DIS->getFile();
   unsigned LineNum = DIS->getLine();
 

llvm/test/Transforms/Coroutines/coro-split-dbg.ll

@@ -77,7 +77,7 @@ attributes #9 = { noduplicate }
 !llvm.module.flags = !{!3, !4}
 !llvm.ident = !{!5}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 4.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
 !1 = !DIFile(filename: "coro.c", directory: "/home/gor/build/bin")
 !2 = !{}
 !3 = !{i32 2, !"Dwarf Version", i32 4}