🚀 go-pugleaf

On the DecStation, immediate constants are limited to 16 bits where
the highest bit is sign extended.

gcc generates some immediate constants that are too large.
Unfortunately, a bug in the mips as doesn't generate an error, but
instead treats large positive constants as negative ones.

Enclosed is a test case, sample run, and resulting assembly.

main()
{
  char* s[0xfffff];
}

32 Huey.Stanford.EDU> gcc -v -S -O big.c
gcc version 1.36
 /usr/local/lib/gcc-cpp -v -undef -D__GNUC__ -Dmips -Dunix -Dultrix -D__mips__ -D__unix__ -D__ultrix__ -D__OPTIMIZE__ -DR3000 -DLANGUAGE_C -DMIPSEL -DSYSTYPE_BSD big.c /usr/tmp/cca00609.cpp
GNU CPP version 1.36
 /usr/local/lib/gcc-cc1 /usr/tmp/cca00609.cpp -O -fstrength-reduce -fomit-frame-pointer -quiet -dumpbase big.c -O -version -o big.s
GNU C version 1.36 (MIPS 1.10) <DECStation>
 compiled by GNU C version 1.36.
default target switches: -munix -mnofixed-ovfl -mG0 -mG1

 #	.verstamp	2 0
gcc_compiled.:
.text
	.align 2
	.globl main
	.ent	main
main:
	subu	$29,4194312	# saveregs=    8
	.frame	$30,0,$31
	.mask	0x40000000,-4194308
	sw	$30,4($29)
	addiu	$30,$29,4194312	# define fp
	addu	$8,$0,$30	# don't trust sp?
	lw	$30,-4194308($8)
	addu	$29,$0,$8	# sp not trusted  here 
	j	$31
 	.end	main
--
Peter Ham			PO Box 3430	(h)(415) 322-4390
MS Computer Science Student	Stanford, CA	ham@cs.stanford.edu
Stanford University 		94309		(o)(415) 723-2067