VAX/testsuite: Remove notsi comparison elimination regressions

VAX/testsuite: Remove notsi comparison elimination regressions

Remove fallout from commit 0bd675183d94 ("match.pd: Add ~(X - Y) -> ~X
+ Y simplification [PR96685]") and paper over the regression caused as
it is not the matter of the test cases affected.

Previously assembly like this:

	.text
	.align 1
.globl eq_notsi
	.type	eq_notsi, @function
eq_notsi:
	.word 0	# 35	[c=0]  procedure_entry_mask
	subl2 $4,%sp	# 46	[c=32]  *addsi3
	mcoml 4(%ap),%r0	# 32	[c=16]  *one_cmplsi2_ccz
	jeql .L1		# 34	[c=26]  *branch_ccz
	addl2 $2,%r0	# 31	[c=32]  *addsi3
.L1:
	ret		# 40	[c=0]  return
	.size	eq_notsi, .-eq_notsi

was produced.  Now this:

	.text
	.align 1
.globl eq_notsi
	.type	eq_notsi, @function
eq_notsi:
	.word 0	# 36	[c=0]  procedure_entry_mask
	subl2 $4,%sp	# 48	[c=32]  *addsi3
	movl 4(%ap),%r0	# 33	[c=16]  *movsi_2
	cmpl %r0,$-1	# 34	[c=8]  *cmpsi_ccz/1
	jeql .L3		# 35	[c=26]  *branch_ccz
	subl3 %r0,$1,%r0	# 32	[c=32]  *subsi3/1
	ret		# 27	[c=0]  return
.L3:
	clrl %r0		# 31	[c=2]  *movsi_2
	ret		# 41	[c=0]  return
	.size	eq_notsi, .-eq_notsi

is, which cannot work with post-reload comparison elimination, due to
the comparison against -1 rather than 0.

Use subtraction from a constant then rather than addition as the former
operation is not transformed, removing these regressions:

FAIL: gcc.target/vax/cmpelim-eq-notsi.c   -O1   scan-rtl-dump-times cmpelim "deleting insn with uid" 1
FAIL: gcc.target/vax/cmpelim-eq-notsi.c   -O1   scan-assembler-not \t(bit|cmpz?|tst).
FAIL: gcc.target/vax/cmpelim-eq-notsi.c   -O1   scan-assembler one_cmplsi[^ ]*_ccz(/[0-9]+)?\n
FAIL: gcc.target/vax/cmpelim-lt-notsi.c   -O1   scan-rtl-dump-times cmpelim "deleting insn with uid" 1
FAIL: gcc.target/vax/cmpelim-lt-notsi.c   -O1   scan-assembler-not \t(bit|cmpz?|tst).
FAIL: gcc.target/vax/cmpelim-lt-notsi.c   -O1   scan-assembler one_cmplsi[^ ]*_ccn(/[0-9]+)?\n

and likewise across some of the other the optimization levels verified.

The LE variant appears unaffected as the new transformation produces
slightly different although still suboptimal code:

	.text
	.align 1
.globl le_notsi
	.type	le_notsi, @function
le_notsi:
	.word 0	# 27	[c=0]  procedure_entry_mask
	subl2 $4,%sp	# 34	[c=32]  *addsi3
	movl 4(%ap),%r1	# 23	[c=16]  *movsi_2
	mcoml %r1,%r0	# 24	[c=8]  *one_cmplsi2_ccnz
	jleq .L1		# 26	[c=26]  *branch_ccnz
	subl3 %r1,$1,%r0	# 22	[c=32]  *subsi3/1
.L1:
	ret		# 32	[c=0]  return
	.size	le_notsi, .-le_notsi

but update the test case too, for consistency with the other two.

	gcc/testsuite/
	* gcc.target/vax/cmpelim-eq-notsi.c: Use subtraction from a
	constant then rather than addition.
	* gcc.target/vax/cmpelim-le-notsi.c: Likewise.
	* gcc.target/vax/cmpelim-lt-notsi.c: Likewise.