CALLER_SAVE/RESTORE in CCalls

[Sven Panne]

Currently the C code generated for consecutive CCalls is something like that
(taken from HOpenGL examples, what else? :-):

        ...
	{
	StgFloat _ccall_arg1=(StgFloat)0.75;
	StgFloat _ccall_arg2=(StgFloat)0.25;
	StgFloat _ccall_arg3=(StgFloat)0.0;
	CALLER_SAVE_SYSTEM
	(glVertex3f((_ccall_arg1),(_ccall_arg2),(_ccall_arg3)));
	CALLER_RESTORE_SYSTEM
	}
	{
	StgFloat _ccall_arg1=(StgFloat)0.75;
	StgFloat _ccall_arg2=(StgFloat)0.75;
	StgFloat _ccall_arg3=(StgFloat)0.0;
	CALLER_SAVE_SYSTEM
	(glVertex3f((_ccall_arg1),(_ccall_arg2),(_ccall_arg3)));
	CALLER_RESTORE_SYSTEM
	}
        ...

This is a bit unfortunate, because this way gcc is unable to nuke no-op
CALLER_RESTORE_SYSTEM/CALLER_SAVE_SYSTEM pairs. I 'm quite sure that
the code in the good old times for this was something like:

        ...
	CALLER_SAVE_SYSTEM
	{
	StgFloat _ccall_arg1=(StgFloat)0.75;
	StgFloat _ccall_arg2=(StgFloat)0.25;
	StgFloat _ccall_arg3=(StgFloat)0.0;
	(glVertex3f((_ccall_arg1),(_ccall_arg2),(_ccall_arg3)));
	}
	CALLER_RESTORE_SYSTEM   // !!!
	CALLER_SAVE_SYSTEM      // !!!
	{
	StgFloat _ccall_arg1=(StgFloat)0.75;
	StgFloat _ccall_arg2=(StgFloat)0.75;
	StgFloat _ccall_arg3=(StgFloat)0.0;
	(glVertex3f((_ccall_arg1),(_ccall_arg2),(_ccall_arg3)));
	}
	CALLER_RESTORE_SYSTEM
        ...

gcc is/was clever enough to omit the code for the marked lines. Changing
this in PprAbsC looks easy, or do I miss something here?

And a related question: What's the reason for the local vars in the above
calls? The following looks a bit simpler:
        ...
	CALLER_SAVE_SYSTEM
	glVertex3f(((StgFloat)0.75, (StgFloat)0.25, (StgFloat)0.0);
	CALLER_RESTORE_SYSTEM   // !!!
	CALLER_SAVE_SYSTEM      // !!!
	glVertex3f(((StgFloat)0.75, (StgFloat)0.75, (StgFloat)0.0);
	CALLER_RESTORE_SYSTEM
        ...

Apart from that, the generated code looks quite cool.

Cheers,
   Sven "back-at-the-bleeding-edge" P.