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From: chip@ateng.UUCP (Chip Salzenberg)
Newsgroups: comp.lang.c
Subject: Re: asm statements & the stack
Message-ID: <33@ateng.UUCP>
Date: Fri, 9-Oct-87 13:07:33 EDT
Article-I.D.: ateng.33
Posted: Fri Oct  9 13:07:33 1987
Date-Received: Mon, 12-Oct-87 06:08:45 EDT
References: <110@teletron.UUCP>
Reply-To: chip@ateng.UUCP (Chip Salzenberg)
Organization: A.T. Engineering, Tampa, FL
Lines: 29

In article <110@teletron.UUCP> andrew@teletron.UUCP (Andrew Scott) writes:
>
>	#define disable	asm("mov.w %sr,-(%sp)"); asm("mov.w &0x2700,%sr")
>	/* push current status register on stack, mask out interrupts */
>
>	#define restore	asm("mov.w (%sp)+,%sr")
>	/* restore status register from stack save location */
>
>The compiler I use (stock AT&T /bin/cc) does a wierd thing upon the call to foo.
>It allocates one more longword than necessary when creating foo's stack frame.

This is a feature!  Your C code runs faster as a result.

Try the following:

#define disable { asm("mov.w %sr,(%sp)"); \
		  asm("subq.l &4,%sp"); \
		  asm("mov.w &0x2700,%sr"); }

#define enable  { asm("addq.l &4,%sp"); \
		  asm("mov.w (%sp),%sr"); }

>	Andrew

-- 
Chip Salzenberg         "chip@ateng.UUCP"  or  "{uunet,usfvax2}!ateng!chip"
A.T. Engineering        My employer's opinions are not mine, but these are.
   "Gentlemen, your work today has been outstanding.  I intend to recommend
   you all for promotion -- in whatever fleet we end up serving."   - JTK