On Sat, Dec 14, 2013 at 09:14:34PM +0100, Tom de Vries wrote: > I wonder if OUTGOING_REG_PARM_STACK_SPACE makes a difference here. > > If OUTGOING_REG_PARM_STACK_SPACE == 0, it is the responsibility of > the callee to allocate the area reserved for arguments passed in > registers. AFAIU, both functions a and b would do that in their own > stack frame, and there's no need to test for reg_parm_stack_space != > REG_PARM_STACK_SPACE (current_function_decl). > > If OUTGOING_REG_PARM_STACK_SPACE != 0, it is the responsibility of > the caller to allocate the area reserved for arguments passed in > registers. Which means that function a and b share the space > allocated by the caller of function a. > AFAIU, what is required is reg_parm_stack_space <= > REG_PARM_STACK_SPACE (current_function_decl).
Hi Tom, I happened to be looking at this code a few weeks ago as part of the PowerPC64 ELFv2 ABI work. I missed seeing the fndecl / current_function_decl bug, but came to the same conclusion as you do above regarding reg_parm_stack_space. In fact, I think you can go a little further. Not all changes in OUTGOING_REG_PARM_STACK_SPACE are bad. If the current function has OUTGOING_REG_PARM_STACK_SPACE non-zero then a sibcall to a function with OUTGOING_REG_PARM_STACK_SPACE zero ought to be OK. So.. #ifdef REG_PARM_STACK_SPACE - /* If outgoing reg parm stack space changes, we can not do sibcall. */ - || (OUTGOING_REG_PARM_STACK_SPACE (funtype) - != OUTGOING_REG_PARM_STACK_SPACE (TREE_TYPE (current_function_decl))) - || (reg_parm_stack_space != REG_PARM_STACK_SPACE (fndecl)) + || (OUTGOING_REG_PARM_STACK_SPACE (funtype) + && (!OUTGOING_REG_PARM_STACK_SPACE (TREE_TYPE (current_function_decl)) + || (reg_parm_stack_space + > REG_PARM_STACK_SPACE (current_function_decl)))) #endif -- Alan Modra Australia Development Lab, IBM
