---snip---
The ELF spec at http://www.sco.com/developers/gabi/ says, "In each
symbol table, all symbols with STB_LOCAL binding precede the weak and
global symbols," and that sh_info is the index of the first non-local
symbol.
I was mixing local and global symbols and setting sh_info to zero. I
also forgot to set the type of the .shstrtab section.
---snip---
assembler directives, ha16() and has16(), for the upper half; has16() applies
the sign adjustment. .powerpcfixup is now gone, as we generate the relocation
in ha*() instead. Add special logic to the linker for undoing and redoing the
sign adjustment when reading/writing fixups. Tests still pass.
Convert each ack.out symbol to ELF, preserving its name and value, and
some but not all other symbol info. The ELF symbol table comes with
ELF section headers. If the input file has no symbols (ack -Rled-s),
then the output file has no ELF section headers.
Append the symbol table and section headers to the ELF file. Linux
ignores this appended info when it execs the file. The info might
pollute the last page of the ELF segment, but Linux clears this
pollution. Tools like nm and gdb can read the ELF symbol table.
I include code to translate debugger symbols to an ELF .stab section.
I did not test this code, because I did not find a platform that can
put S_STB symbols in the ack.out file.
Put end of sentence at end of line. This is roff(7) syntax so the
formatter can make spacing between sentences.
Use the macro .PP to break paragraphs. Use bold for the command name
in SYNOPSIS, to match other ack manuals.
No change to linuxppc and qemuppc. They continue to run ego without
any descr file.
I copied m68020.descr to powerpc.descr and changed some numbers. My
numbers are guesses; I know little about PowerPC cycle counts, and
almost nothing about ego. This powerpc.descr causes most of the
example programs to shrink in size (without descr -> with descr):
65429 -> 57237 hilo_b.osxppc -8192
36516 -> 32420 hilo_c.osxppc -4096
55782 -> 51686 hilo_mod.osxppc -4096
20096 -> 20096 hilo_p.osxppc 0
8813 -> 8813 mandelbrot_c.osxppc 0
93355 -> 89259 paranoia_c.osxppc -4096
92751 -> 84559 startrek_c.osxppc -8192
(Each file has 2 Mach segments, then a symbol table. Each segment
takes a multiple of 4096 bytes. When the code shrinks, we lose a
multiple of 4096 bytes.)
I used "ack -mosxppc -O6 -c.so" to examine the assembly code for
hilo.mod and mandelbrot.c, both without and with descr. This reveals
optimizations made only with descr, from 2 ego phases: SP (stack
pollution) and RA (register allocation). In hilo.mod, SP deletes some
instructions that remove items from the stack. These items get
removed when the function returns. In both hilo.mod and mandelbrot.c,
RA moves some values into local variables, so ncg can make them into
register variables. This shrinks code size, probably because register
variables get preserved across function calls. More values stay in
registers, and ncg emits shorter code.
I believe that the ego descr file uses (time,space) tuples but the ncg
table uses (space,time) tuples. This is confusing. Perhaps I am
wrong, and some or all tuples are backwards. My time values are the
cycle counts in latency from the MPC7450 Reference Manual (but not
including complications like "store serialization").
In powerpc.descr, I give the cost for saving and restoring registers
as if I was using chains of stw and lwz instructions. Actually ncg
uses single stmw and lmw instructions with at least 2 instructions.
The (time,space) for stmw and lmw would be much less than the
(time,space) for chains of stw and lwz. But this ignores the pipeline
of the MPC7450. The chains of stw and lwz may run faster than stmw
and lmw in the pipeline, because the throughput may be better than the
latency. By using the wrong values for (time,space), I'm trying to
tell ego that stmw and lmw are not better than chains of stw and lwz.
This brings in David Given's PowerPC changes, including the addition
of the modern code generator (mcg) for PowerPC.
Resolve minor conflicts in top build.lua and util/led/main.c
This uses uint32_t for the base, file offset, and alignment of each
section, to be consistent with the usage of uint32_t in h/out.h
Also declare setbit() as static.
corresponding invocation in the ncg table so the same helpers can be used for
both mcg and ncg. Add a new IR opcode, FARJUMP, which jumps to a helper
function but saves volatile registers.
unlink("core") doesn't work with OpenBSD, where core dumps have names
like "ncg.core". Users who don't want core dumps can turn them off
with "ulimit -c 0" in sh(1). Then the system doesn't write a core
dump. That's better than writing core then unlinking it.
This commit changes how ack(1) parses backslashes in its descr files.
Before this commit, ack set the high bit of each character escaped by
a backslash, and later cleared all high bits in command arguments, but
this lost the high bits in non-ASCII filenames. After this commit,
ack keeps backslashes in strings while processing them. Functions
scanvars(), scanexpr(), doassign(), unravel(), addargs() now
understand backslashes. I remove from ack_basename() the warning
about non-ASCII characters.
This commit makes some incompatible changes for backslashes in descr
files. None of our descr files uses backslashes, except for those
backslashes that continue lines, and there are no changes for those
backslashes. The problem with non-ASCII filenames had its cause in a
feature that we weren't using.
With this commit, ack now understands backslashes after the = sign in
both "var NAME=value" and "mapflag -flag NAME=value". Before, ack
never scanned backslashes in "var" lines, so "var A=\{B}" failed to
prevent expansion of B. Now it does. Before, ack did scan for
backslashes in the "-flag NAME=" part of "mapflag" lines. Now it
doesn't, so it is no longer possible to map a flag that contains a
literal space, tab, or star "*".
I removed the expansion of "{{" to "{". One can use "\{" for a
literal "{", and "\{" now works in "var" lines. Before and now, ack
never expanded "{" in flags for "mapflag", so the correct way to map a
literal flag "-{" remains "mapflag -{ ...", not "mapflag -{{ ...".
(The other way "mapflag -\{ ..." stops working with this commit.)
Backslashes in strange places, like "{NA\ME}", probably have different
behavior now.
Backslashes in "program" lines now work. Before, ack scanned for
backslashes there but forgot to clear the high bits later.
Escaping < or > as \< or \> now works, and prevents substitution of
the input or output file paths. Before, ack only expanded the first <
or > in each argument. Now, it expands every unescaped < or > in an
argument, but this is an accident of how I rewrote the code. I don't
suggest to put more than one each of < or > in a command. The code no
longer optimizes away its recursive calls when the argument is "<".
The code continues to set or clear the high bit NO_SCAN on the first
characters of flags. This doesn't seem to be a problem, because flags
usually begin with an ASCII hyphen '-'.
If fork() fails, then report a fatal error. Don't spin the cpu
retrying fork() until it succeeds. It can fail when we reach a limit
on the number of processes. Spinning on the cpu would slow down other
processes when we want them to exit. This would get bad if we had a
parallel build with multiple ack processes spinning.
new= newvar(name) takes ownership of the string and might free its
memory. Don't print name. Do print new->v_name.
Also #include <string.h> for strcmp().
Declare most functions before using them. I declare some functions in
ack.h and some in trans.h (because trans.h declares type trf). I
leave declarations of scanb() and scanvars() in .c files because they
need type growstring. (I can't #include "grows.h" in another header
file as long as grows.h doesn't guard against multiple inclusion.)
Functions used within one file become static. I remove a few tiny
functions. I move a few functions or declarations to more convenient
places. Some functions now return void instead of a garbage int.
I feel that keyword "register" is obsolete, so I removed it from where
I was editing. This commit doesn't touch mktables.c
register 'type'; now use int/float/long/double throughout to identify
registers. Lots of register allocator tweaks and table bugfixes --- we now get
through the dreading Mathlib.mod!
and epilogues. mcgg now exports some useful data as headers. Start factoring
out some of the architecture-specific bits into an architecture-specific file.
attributes when allocating. Unfortunately, backward edges don't work (because
the limited def-use chain stuff doesn't work across basic blocks). Needs more
thought.
turned into generic ones (as they'll be useful everywhere). Node arguments for
predicates require the '%' prefix for consistency. Hex numbers are permitted.
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.
mcg can track individual hop inputs and outputs (needed for live range
analysis!); the register allocator now puts the basic blocks into the right
order in preparation for live range analysis.
to make special nodes like NOP work properly). Realise that the way I'm dealing
with the instruction selector is all wrong; I need to physically copy chunks of
tree to give to burg (so I can terminate them correctly).
inasmuch as it looks better before register allocation. Basic blocks now know
their own successors and predecessors (after a certain point in the IR
processing).
functions. Not convinced that semantic types are actually working --- there are
still problems with earlier statements leaving things in the wrong registers.
instructions can be turned on and off based on their parameters. New lexer
using a lexer. Now quite a lot of the way towards being a real instruction
selector.
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).
calculated incorrectly because of overflow errors.
Replace it with an extended RELOPPC relocation which understands addis/ori
pairs; add an la pseudoop to the assembler which generates these and the
appropriate relocation. Make good.
--HG--
branch : dtrg-experimental-powerpc-branch
cf/cf_loop.c and share/put.c tried to read the next pointer in an
element of a linked list after freeing the element. ud/ud_copy.c
tried to read beyond the end of the _defs_ array: it only has
_nrexpldefs_ elements, not _nrdefs_ elements.
These bugs caused core dumps on OpenBSD. Its malloc() put _defs_ near
the end of a page, so reading beyond the end crossed into an unmapped
page. Its free() wrote junk bytes and changed the next pointer to
0xdfdfdfdfdfdfdfdf.
and generate invalid calls to the optimisers.
Previously ego would generate a temporary file template that looked like
/tmp/ego.A.BB.XXXXXX, call mktemp() on it to randomise the XXXXXX, and then
replace A and BB with data.
However, it used strrchr to find the A and B. Which would fine, except when
mktemp produced an A or a B in the randomised part...
This code was written on 4 March 1991. I was 16.
This needed lots of refactoring to ego --- not all platforms have ego descr
files, and ego will just crash if you invoke it without one. I think originally
it was never intended that these platforms would be used at -O2 or above.
Plats now only specify the ego descr file if they have one.
