Preparation for golang.org/s/go13linker work.
This CL does not build by itself. It depends on 35740044
and 35790044 and will be submitted at the same time.
R=iant
CC=golang-dev
https://golang.org/cl/34590045
This eliminates ~75% of the nil checks being emitted,
on all architectures. We can do better, but we need
a bit more general support from the compiler, and
I don't want to do that so close to Go 1.2.
What's here is simple but effective and safe.
A few small code generation cleanups were required
to make the analysis consistent on all systems about
which nil checks are omitted, at least in the test.
Fixes#6019.
R=ken2
CC=golang-dev
https://golang.org/cl/13334052
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
Now there's only one copy of the flow graph construction
and dominator computation, and different optimizations
can attach different annotations to the instructions.
R=ken2
CC=golang-dev
https://golang.org/cl/12797045
Code in gc/popt.c is compiled as part of 5g, 6g, and 8g,
meaning it can use arch-specific headers but there's
just one copy of the code.
This is the same arrangement we use for the portable
code generation logic in gc/pgen.c.
Move fixjmp and noreturn there to get the ball rolling.
R=ken2
CC=golang-dev
https://golang.org/cl/12789043
