On Mon, Sep 19, 2011 at 9:49 AM, Peter Maydell <peter.mayd...@linaro.org>wrote:
> On 19 September 2011 13:06, Xin Tong Utoronto <x.t...@utoronto.ca> wrote: > > There are 2 files on helpers in target-ppc and target-i386 ( op-helper.c > > helper.c), what are their differences ? also, what kind of functions are > > typically emulated using helpers ? > > The key difference is that op_helper.c is compiled with compiler > flags and includes header files that give it access to a global > variable 'CPUState *env' which is kept in a fixed CPU register > during execution of translated code. This is easier for the tcg to call ? > helper.c (and other foo_helper.c > files) are built as regular C files, and so if they need access to the > CPU state it has to be passed into the helper as an explicit parameter. > We're currently trying to cut back on the use of the implicit global, > so new helper functions should probably go in helper.c. > > Why do we want to cut back on the use of the implicit global ? what is the criteria for a function to be in the implicit global list ? > > also, what kind of functions are typically emulated using helpers ? > > Anything that seems too hard to do inline :-) tcg/README has a > paragraph at the end giving some rules of thumb. > > -- PMM > -- Kind Regards Xin Tong
