chris@umcp-cs.UUCP (Chris Torek) (11/24/84)
Index: ucb/pascal/src/pccaseop.c 4.2BSD Fix
Description:
The Pascal compiler generates case instructions "by hand"
when given the -J option. However, in doing so, it emits
"blssu" instructions for out-of-range entries; sometimes
the destination label of this branch is too far away for
the Vax (the branch must be a byte displacement from the
current PC). Normally, the compiler uses "jxxx" instructions,
which the assembler expands as necessary; but here, someone
goofed.
Repeat-By:
Compile an enourmous Pascal program using -J. In particular,
try compiling TeX after installing the "others" case clause.
Fix:
Emit "jlssu" instead of "blssu". Another alternative would
be to rearrange things so that the "case range error" code
lies right after the "jmp" instruction used to branch to
one of the in-range statements; however, this would require
much more work, so guess which one I did?
Here's a context diff, even though there's only ONE "blssu"
in the entire ucb/pascal/src directory...
RCS file: RCS/pccaseop.c,v
retrieving revision 1.2
diff -b -c -r1.2 pccaseop.c
*** /tmp/,RCSt1002891 Fri Nov 23 23:38:42 1984
--- pccaseop.c Fri Nov 23 23:37:44 1984
***************
*** 286,292
putprintf(" subl2 $%d,%s", 0, ctab[1].cconst, FORCENAME);
putprintf(" cmpl $%d,%s", 0,
ctab[count].cconst - ctab[1].cconst, FORCENAME);
! putprintf(" blssu %s%d", 0, LABELPREFIX, ctab[0].clabel);
putprintf(" ashl $2,%s,%s", 0, FORCENAME, FORCENAME);
putprintf(" jmp *%s%d(%s)", 0,
LABELPREFIX, fromlabel, FORCENAME);
--- 286,292 -----
putprintf(" subl2 $%d,%s", 0, ctab[1].cconst, FORCENAME);
putprintf(" cmpl $%d,%s", 0,
ctab[count].cconst - ctab[1].cconst, FORCENAME);
! putprintf(" jlssu %s%d", 0, LABELPREFIX, ctab[0].clabel);
putprintf(" ashl $2,%s,%s", 0, FORCENAME, FORCENAME);
putprintf(" jmp *%s%d(%s)", 0,
LABELPREFIX, fromlabel, FORCENAME);
--
(This line accidently left nonblank.)
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (301) 454-7690
UUCP: {seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet: chris@umcp-cs ARPA: chris@maryland