The new feature "reglap" allows two sizes of floating-point register
variables (reg_float), if each register overlaps a single register of
the other size. PowerPC ncg uses reglap to define 4-byte instances
of f14 to f31 that overlap the 8-byte instances.
When ncgg sees the definition of fs14("f14")=f14, it removes the
8-byte f14 from its rvnumbers array, and adds the 4-byte fs14 in its
place. Later, when ncg puts a variable in fs14, if it is an 8-byte
variable, then ncg switches to the 8-byte f14. The code has
/* reglap */ comments in util/ncgg or #ifdef REGLAP in mach/proto/ncg
reglap became necessary because my commit a20b87c caused PowerPC ego
to allocate reg_float in both 4-byte and 8-byte sizes.
This feature has never been used since its introduction, more than 3
years ago, in David Given's commit c93cb69 of May 8, 2013. The commit
was for "PowerPC and M68K work". I am not undoing the entire commit.
I am only removing the stackadjust and stackoffset() feature.
This commit removes the feature from my branch kernigh-linuxppc. This
removal includes the mach/proto/ncg parts. The default branch already
removed most of the feature, but kept the mach/proto/ncg parts. That
removal happened in commit 81778b6 of May 13, 2013 (which was a merge;
git diff af0dede81778b6). The branch dtrg-experimental-powerpc
merged the default branch but without the removal. That merge was
commit 4703db0f of Sep 15, 2016 (git diff 8c94b134703db0). My branch
kernigh-linuxppc is off branch dtrg-experimental-powerpc, so I can no
longer get the removal by merging default.
David Given described the stackadjust feature in
https://sourceforge.net/p/tack/mailman/message/30814691/
The instruction stackadjust would add a value to the offset, and the
function stackoffset() would return this offset. One would use this
to track sp - fp, then omit the frame pointer by not keeping fp in a
register.
Upon enabling the check, mach/powerpc/ncg/table fails to build as ncgg
gives many errors of "Previous rule impossible on empty stack". David
Given reported this problem in 2013:
https://sourceforge.net/p/tack/mailman/message/30814694/
Commit c93cb69 commented out the error in util/ncgg/cgg.y to disable
the Hall check. This commit enables it again. In ncgg, the Hall
check is checking that a rule is possible with an empty fake stack.
It would be possible if ncg can coerce the values from the real stack
to the fake stack. The powerpc table defined coercions from STACK to
{FS, %a} and {FD, %a}, but the Hall check didn't understand the
coercions and rejected each rule "with FS" or "with FD".
This commit removes the FS and FD tokens and adds a new group of FSREG
registers for single-precision floats, while keeping FREG registers
for double precision. The registers overlap, with each FSREG
containing one FREG, because it is the same register in PowerPC
hardware. FS tokens become FSREG registers and FD tokens become FREG
registers. The Hall check understands the coercions from STACK to
FSREG and FREG. The idea to define separate but overlapping registers
comes from the PDP-11 table (mach/pdp/ncg/table).
This commit also removes F0 from the FREG group. This is my attempt
to keep F0 off the fake stack, because one of the stacking rules uses
F0 as a scratch register (FSCRATCH).
directories --- wrangling descr files was too hard. C programs can be built
for cpm, pc86, linux386, linux68k!
--HG--
branch : dtrg-buildsystem
rename : util/ack/build.mk => util/led/build.mk
rename : util/LLgen/build.mk => util/topgen/build.mk
These files "magically reappeared" after the conversion from CVS to
Mercurial. The old CVS repository deleted these files but did not
record *when* it deleted these files. The conversion resurrected these
files because they have no history of deletion. These files were
probably deleted before year 1995. The CVS repository begins to record
deletions around 1995.
These files may still appear in older revisions of this Mercurial
repository, when they should already be deleted. There is no way to fix
this, because the CVS repository provides no dates of deletion.
See http://sourceforge.net/mailarchive/message.php?msg_id=29823032
constant or not by comparing it with 'end', which presumably points at
the top of the BSS. In fact, on Linux it evaluates to NULL, and on OSX it
doesn't exist at all, so it appears to be unnecessary.
