Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site umcp-cs.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!think!harvard!seismo!umcp-cs!chris
From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.bugs.4bsd
Subject: Re: /lib/c2 optimizes calls instructions
Message-ID: <1326@umcp-cs.UUCP>
Date: Thu, 22-Aug-85 01:58:56 EDT
Article-I.D.: umcp-cs.1326
Posted: Thu Aug 22 01:58:56 1985
Date-Received: Sat, 24-Aug-85 17:31:12 EDT
References: <2064@ukma.UUCP>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 127

>Index: /lib/c2, BRL-Unix release 3, likely appears in other 4.?BSD.

>Problem: Calls instructions have a format "calls <const-#-of-args>,<addr>".
>	The <const-#-of-args> argument will sometimes be "optimized" into
>	a register reference.  This isn't necessary, and breaks the
>	massager which helps create the code in the kernel.

It saves a little teensy bit of time.  Anyway, here's how to work
around it.  I added a new flag to /lib/c2 (-c) but it should be
obvious how to make it always do what -c does.

First, change /usr/src/lib/c2/c20.c to handle "-c".  (Beware, these
are to what amounts to the 4.3BSD c2; your code may vary slightly.)

RCS file: RCS/c20.c,v
retrieving revision 1.1
diff -c2 -r1.1 c20.c
*** /tmp/,RCSt1015521	Thu Aug 22 01:45:07 1985
--- c20.c	Thu Aug 22 01:44:13 1985
***************
*** 15,18
  caddr_t sbrk();
  int ioflag;
  int fflag;
  long	isn	= 2000000;

--- 15,19 -----
  caddr_t sbrk();
  int ioflag;
+ int cflag;
  int fflag;
  long	isn	= 2000000;
***************
*** 57,60
  			if ((*argv)[1]=='i') ioflag++;
  			else if ((*argv)[1]=='f') fflag++;
  			else nflag++;
  		} else if (infound==0) {

--- 58,62 -----
  			if ((*argv)[1]=='i') ioflag++;
  			else if ((*argv)[1]=='f') fflag++;
+ 			else if ((*argv)[1]=='c') cflag++;
  			else nflag++;
  		} else if (infound==0) {


Second, modify the optimizer code in /usr/src/lib/c2/c21.c to check
cflag before optimizing "calls" constants.  This also includes a
fix from Donn Seeley for a longstanding fencepost error:

RCS file: RCS/c21.c,v
retrieving revision 1.1
diff -c2 -r1.1 c21.c
*** /tmp/,RCSt1015526	Thu Aug 22 01:45:24 1985
--- c21.c	Thu Aug 22 01:44:49 1985
***************
*** 14,17
  #define NUSE 6
  int ioflag;
  int biti[NUSE] = {1,2,4,8,16,32};
  int bitsize[] = {	/* index by type codes */

--- 14,18 -----
  #define NUSE 6
  int ioflag;
+ int cflag;
  int biti[NUSE] = {1,2,4,8,16,32};
  int bitsize[] = {	/* index by type codes */
***************
*** 509,512
  		break;
  
  /* .rx,.rx,.rx */
  	case PROBER:

--- 510,521 -----
  		break;
  
+ /* .rx,.rx */
+ 	case CALLS:
+ 		if (cflag)	/* don't optimize constants in calls */
+ 			break;
+ 		/* fall through */
+ 	case MTPR:
+ 	case CMP:
+ 	case BIT:
  /* .rx,.rx,.rx */
  	case PROBER:
***************
*** 514,522
  	case CASE:
  	case MOVC3:
- /* .rx,.rx */
- 	case MTPR:
- 	case CALLS:
- 	case CMP:
- 	case BIT:
  		splitrand(p);
  		/* fool repladdr into doing right number of operands */

--- 523,526 -----
  	case CASE:
  	case MOVC3:
  		splitrand(p);
  		/* fool repladdr into doing right number of operands */
***************
*** 724,728
  			if (!equstr(regs[RT3],"-(sp)")) p->combop=T(MOVA,BYTE);
  			else {p->combop=T(PUSHA,BYTE); *cp2=0;}
! 			if (uses[r]==0) {uses[r]=p; regs[r][0]=OPX<<4;}
  			p->pop=0;
  		}

--- 728,735 -----
  			if (!equstr(regs[RT3],"-(sp)")) p->combop=T(MOVA,BYTE);
  			else {p->combop=T(PUSHA,BYTE); *cp2=0;}
! 			if (r < NUSE && uses[r] == 0) {
! 				uses[r]=p;
! 				regs[r][0]=OPX<<4;
! 			}
  			p->pop=0;
  		}
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@maryland