The compilers assume they can generate temporary variables
as needed to preserve the right semantics or simplify code
generation and the back end will still generate good code.
This turns out not to be true. The back ends will only
track the first 128 variables per function and give up
on the remainder. That needs to be fixed too, in a later CL.
This CL merges temporary variables with equal types and
non-overlapping lifetimes using the greedy algorithm in
Poletto and Sarkar, "Linear Scan Register Allocation",
ACM TOPLAS 1999.
The result can be striking in the right functions.
Top 20 frame size changes in a 6g godoc binary by bytes saved:
5464 1984 (-3480, -63.7%) go/build.(*Context).Import
4456 1824 (-2632, -59.1%) go/printer.(*printer).expr1
2560 80 (-2480, -96.9%) time.nextStdChunk
3496 1608 (-1888, -54.0%) go/printer.(*printer).stmt
1896 272 (-1624, -85.7%) net/http.init
2688 1400 (-1288, -47.9%) fmt.(*pp).printReflectValue
2800 1512 (-1288, -46.0%) main.main
3296 2016 (-1280, -38.8%) crypto/tls.(*Conn).clientHandshake
1664 488 (-1176, -70.7%) time.loadZoneZip
1760 608 (-1152, -65.5%) time.parse
4104 3072 (-1032, -25.1%) runtime/pprof.writeHeap
1680 712 ( -968, -57.6%) go/ast.Walk
2488 1560 ( -928, -37.3%) crypto/x509.parseCertificate
1128 392 ( -736, -65.2%) math/big.nat.divLarge
1528 864 ( -664, -43.5%) go/printer.(*printer).fieldList
1360 712 ( -648, -47.6%) regexp/syntax.(*parser).factor
2104 1528 ( -576, -27.4%) encoding/asn1.parseField
1064 504 ( -560, -52.6%) encoding/xml.(*Decoder).text
584 48 ( -536, -91.8%) html.init
1400 864 ( -536, -38.3%) go/doc.playExample
In the same godoc build, cuts the number of functions with
too many vars from 83 to 32.
R=ken2
CC=golang-dev
https://golang.org/cl/12829043
STRINGSZ (200) is fine for lines generated by things like
instruction dumps, but an error containing a couple file
names can easily exceed that, especially on Macs with
the ridiculous default $TMPDIR.
R=ken2
CC=golang-dev
https://golang.org/cl/11199043
That is, move the pc/ln table and the symbol table
into the read-only data segment. This eliminates
the need for a special load command to map the
symbol table into memory, which makes the
information available on systems that couldn't handle
the magic load to 0x99000000, like NaCl and ARM QEMU
and Linux without config_highmem=y. It also
eliminates an #ifdef and some clumsy code to
find the symbol table on Windows.
The bad news is that the binary appears to be bigger
than it used to be. This is not actually the case, though:
the same amount of data is being mapped into memory
as before, and the tables are still read-only, so they're
still shared across multiple instances of the binary as
they were before. The difference is just that the tables
aren't squirreled away in some section that "size" doesn't
know to look at.
This is a checkpoint.
It probably breaks Windows and breaks NaCl more
than it used to be broken, but those will be fixed.
The logic involving -s needs to be revisited too.
Fixes#871.
R=ken2
CC=golang-dev
https://golang.org/cl/2587041
The Plan 9 tools assume that long is 32 bits.
We converted all instances of long to int32 when
importing the code but missed the print formats.
Because int32 is always int on the compilers we use,
it is never correct to use %lux, %ld, etc. Convert to %ux, %d, etc.
(It matters because on 64-bit gcc, long is 64 bits,
so we were printing 32-bit quantities with 64-bit formats.)
R=ken2
CC=golang-dev
https://golang.org/cl/2491041
* Maintain Sym* list for text with individual
prog lists instead of using one huge list and
overloading p->pcond.
* Comment what each file is for.
* Move some output code from span.c to asm.c.
* Move profiling into prof.c, symbol table into symtab.c.
* Move mkfwd to ld/lib.c.
* Throw away dhog dynamic loading code.
* Throw away Alef become.
* Fix printing of WORD instructions in 5l -a.
Goal here is to be able to handle each piece of text or data
as a separate piece, both to make it easier to load the
occasional .o file and also to make it possible to split the
work across multiple threads.
R=ken2, r, ken3
CC=golang-dev
https://golang.org/cl/2335043
Russ Cox
Ken Thompson
Rob Pike