[clang] [CIR] Upstream support for setjmp & longjmp builtins (PR #178989)

[Andy Kaylor via cfe-commits]

================
@@ -1352,8 +1352,44 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
   case Builtin::BI__builtin_eh_return:
   case Builtin::BI__builtin_unwind_init:
   case Builtin::BI__builtin_extend_pointer:
-  case Builtin::BI__builtin_setjmp:
-  case Builtin::BI__builtin_longjmp:
+    return errorBuiltinNYI(*this, e, builtinID);
+  case Builtin::BI__builtin_setjmp: {
+    Address buf = emitPointerWithAlignment(e->getArg(0));
+    mlir::Location loc = getLoc(e->getExprLoc());
+
+    cir::PointerType ppTy = builder.getPointerTo(builder.getVoidPtrTy());
+    mlir::Value castBuf = builder.createBitcast(buf.getPointer(), ppTy);
----------------
andykaylor wrote:

```suggestion
    cir::PointerType voidPtrTy = builder.getVoidPtrTy();
    cir::PointerType ppTy = builder.getPointerTo(voidPtrTy);
    Adddress castBuf = buf.withElementType(voidPtrTy);
```
This will preserve the alignment that `buf` already has.

https://github.com/llvm/llvm-project/pull/178989