Currently the only mention of go_asm.h is buried in a confusing
section about the runtime-specific go_tls.h header. We actually want
people to use go_asm.h, so this CL adds a section with a proper
discussion of this header. As part of this, we remove the discussion
of go_asm.h from the go_tls.h section and clean up what remains.
I stumbled on this when working on the internal ABI specification. I
wanted to refer to stable documentation on how to access struct fields
from assembly and found there was none.
Change-Id: I0d53741e7685e65794611939e76285f7c82e1d65
Reviewed-on: https://go-review.googlesource.com/c/go/+/286052
Trust: Austin Clements <austin@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Adding the usage of PCALIGN directive for arm64, and updating some
details on using some directives defined in the textflag.h file.
Change-Id: I43d363e3337939bab69b856831caf06803a292d2
Reviewed-on: https://go-review.googlesource.com/c/go/+/227801
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Update the section in asm.html related to PPC64. Remove the line
that says it is in an experimental state, add a link to the
new doc.go file that has all the detail for the Go assembler for
PPC64.
Change-Id: I45d9891669e01d94e2721be576d572e02cd9d2db
Reviewed-on: https://go-review.googlesource.com/c/go/+/183840
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The compiler output shown in the doc is now quite old
(most of the changes happened in Go 1.5).
Update it to be more like what users will actually see.
Also explain how to get literal machine code again.
Prompted by #30968.
Change-Id: I0ce139c3fe299ccc43e85b6aca81c6e0aac1a2df
Reviewed-on: https://go-review.googlesource.com/c/go/+/175757
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
In ARM64 ABI, R18 is the "platform register", the use of which is
OS specific. The OS could choose to reserve this register. In
practice, it seems fine to use R18 on Linux but not on darwin (iOS).
Rename R18 to R18_PLATFORM to prevent accidental use. There is no
R18 usage within the standard library (besides tests, which are
updated).
Fixes#26110
Change-Id: Icef7b9549e2049db1df307a0180a3c90a12d7a84
Reviewed-on: https://go-review.googlesource.com/c/147218
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
mips64 softfloat support is based on mips implementation and introduces
new enviroment variable GOMIPS64.
GOMIPS64 is a GOARCH=mips64{,le} specific option, for a choice between
hard-float and soft-float. Valid values are 'hardfloat' (default) and
'softfloat'. It is passed to the assembler as
'GOMIPS64_{hardfloat,softfloat}'.
Change-Id: I7f73078627f7cb37c588a38fb5c997fe09c56134
Reviewed-on: https://go-review.googlesource.com/108475
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The patch rewrites the content of doc.go file. The file describes some
general rules of the mapping between Go assembly syntax and GNU syntax.
And it gives some Go assembly examples and corresponding GNU assembly
examples.
The patch changes the doc.go to use standard doc comment format so that
the link https://golang.org/cmd/internal/obj/arm64/ can display it.
Assembly document framework is mainly contributed by Eric Fang <Eric.Fang@arm.com>
Documentation work is contributed by Eric Fang and Fannie Zhang <Fannie.Zhang@arm.com>
Change-Id: I8b3f6d6c6b91afdc2c44602e8f796beea905085e
Reviewed-on: https://go-review.googlesource.com/102055
Reviewed-by: Rob Pike <r@golang.org>
We were not being consistent.
Standardize on toolchain.
Change-Id: Id0e756b5214ce4a1341f733634ed95263f03a61c
Reviewed-on: https://go-review.googlesource.com/87017
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
GOMIPS is a GOARCH=mips{,le} specific option, for a choice between
hard-float and soft-float. Valid values are 'hardfloat' (default) and
'softfloat'. It is passed to the assembler as
'GOMIPS_{hardfloat,softfloat}'.
Note: GOMIPS will later also be used for a choice of MIPS instruction
set (mips32/mips32r2).
Updates #18162
Change-Id: I35417db8625695f09d6ccc3042431dd2eaa756a6
Reviewed-on: https://go-review.googlesource.com/37954
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
The plan9.bell-labs.com site has fallen into disrepair.
We'll instead use the site maintained by contributor David du Colombier.
Fixes#14233
Change-Id: I0c702e5d3b091cccd42b288ea32f34d507a4733d
Reviewed-on: https://go-review.googlesource.com/19240
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: David du Colombier <0intro@gmail.com>
Consider this code:
func f(*int)
func g() {
p := new(int)
f(p)
}
where f is an assembly function.
In general liveness analysis assumes that during the call to f, p is dead
in this frame. If f has retained p, p will be found alive in f's frame and keep
the new(int) from being garbage collected. This is all correct and works.
We use the Go func declaration for f to give the assembly function
liveness information (the arguments are assumed live for the entire call).
Now consider this code:
func h1() {
p := new(int)
syscall.Syscall(1, 2, 3, uintptr(unsafe.Pointer(p)))
}
Here syscall.Syscall is taking the place of f, but because its arguments
are uintptr, the liveness analysis and the garbage collector ignore them.
Since p is no longer live in h once the call starts, if the garbage collector
scans the stack while the system call is blocked, it will find no reference
to the new(int) and reclaim it. If the kernel is going to write to *p once
the call finishes, reclaiming the memory is a mistake.
We can't change the arguments or the liveness information for
syscall.Syscall itself, both for compatibility and because sometimes the
arguments really are integers, and the garbage collector will get quite upset
if it finds an integer where it expects a pointer. The problem is that
these arguments are fundamentally untyped.
The solution we have taken in the syscall package's wrappers in past
releases is to insert a call to a dummy function named "use", to make
it look like the argument is live during the call to syscall.Syscall:
func h2() {
p := new(int)
syscall.Syscall(1, 2, 3, uintptr(unsafe.Pointer(p)))
use(unsafe.Pointer(p))
}
Keeping p alive during the call means that if the garbage collector
scans the stack during the system call now, it will find the reference to p.
Unfortunately, this approach is not available to users outside syscall,
because 'use' is unexported, and people also have to realize they need
to use it and do so. There is much existing code using syscall.Syscall
without a 'use'-like function. That code will fail very occasionally in
mysterious ways (see #13372).
This CL fixes all that existing code by making the compiler do the right
thing automatically, without any code modifications. That is, it takes h1
above, which is incorrect code today, and makes it correct code.
Specifically, if the compiler sees a foreign func definition (one
without a body) that has uintptr arguments, it marks those arguments
as "unsafe uintptrs". If it later sees the function being called
with uintptr(unsafe.Pointer(x)) as an argument, it arranges to mark x
as having escaped, and it makes sure to hold x in a live temporary
variable until the call returns, so that the garbage collector cannot
reclaim whatever heap memory x points to.
For now I am leaving the explicit calls to use in package syscall,
but they can be removed early in a future cycle (likely Go 1.7).
The rule has no effect on escape analysis, only on liveness analysis.
Fixes#13372.
Change-Id: I2addb83f70d08db08c64d394f9d06ff0a063c500
Reviewed-on: https://go-review.googlesource.com/18584
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Saying "Power 64" was wrong for reasons I don't remember.
(Those reasons are why we stopped using GOARCH=power64.)
Change-Id: Ifaac78d5733bfc780df01b1a66da766af0b17726
Reviewed-on: https://go-review.googlesource.com/13675
Reviewed-by: Rob Pike <r@golang.org>
Also make the spelling consistent in asm.html
Change-Id: Ifa751eee288fe0634cd317eb827f3e408b199620
Reviewed-on: https://go-review.googlesource.com/12501
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Still to do: ARM64 and PPC64. These architectures are woefully underdocumented.
Change-Id: Iedcf767a7e0e1c931812351940bc08f0c3821212
Reviewed-on: https://go-review.googlesource.com/12110
Reviewed-by: Russ Cox <rsc@golang.org>
The architecture-specific details will be updated and expanded in
a subsequent CL (or series thereof).
Update #10096
Change-Id: I59c6be1fcc123fe8626ce2130e6ffe71152c87af
Reviewed-on: https://go-review.googlesource.com/11954
Reviewed-by: Russ Cox <rsc@golang.org>
e.g. ·Name instead of package·Name for automatic stack map to
be applied from its Go prototype.
The underlying reason is that liblink look up name with suffix
".args_stackmap" for the stackmap coming from its Go prototype,
but all the Go functions are named "".Name as this stage. Thus
an assembly function named package·Name will never find its
stackmap, which is named "".package.Name.args_stackmap.
Perhaps cmd/vet should give a warning for this.
Change-Id: I10d154a73ec969d574d20af877f747424350fbd1
Reviewed-on: https://go-review.googlesource.com/2588
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The file is used by assembly code to define symbols like NOSPLIT.
Having it hidden inside the cmd directory makes it hard to access
outside the standard repository.
Solution: As with a couple of other files used by cgo, copy the
file into the pkg directory and add a -I argument to the assembler
to access it. Thus one can write just
#include "textflag.h"
in .s files.
The names in runtime are not updated because in the boot sequence the
file has not been copied yet when runtime is built. All other .s files
in the repository are updated.
Changes to doc/asm.html, src/cmd/dist/build.c, and src/cmd/go/build.go
are hand-made. The rest are just the renaming done by a global
substitution. (Yay sam).
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/128050043
The runtime has historically held two dedicated values g (current goroutine)
and m (current thread) in 'extern register' slots (TLS on x86, real registers
backed by TLS on ARM).
This CL removes the extern register m; code now uses g->m.
On ARM, this frees up the register that formerly held m (R9).
This is important for NaCl, because NaCl ARM code cannot use R9 at all.
The Go 1 macrobenchmarks (those with per-op times >= 10 µs) are unaffected:
BenchmarkBinaryTree17 5491374955 5471024381 -0.37%
BenchmarkFannkuch11 4357101311 4275174828 -1.88%
BenchmarkGobDecode 11029957 11364184 +3.03%
BenchmarkGobEncode 6852205 6784822 -0.98%
BenchmarkGzip 650795967 650152275 -0.10%
BenchmarkGunzip 140962363 141041670 +0.06%
BenchmarkHTTPClientServer 71581 73081 +2.10%
BenchmarkJSONEncode 31928079 31913356 -0.05%
BenchmarkJSONDecode 117470065 113689916 -3.22%
BenchmarkMandelbrot200 6008923 5998712 -0.17%
BenchmarkGoParse 6310917 6327487 +0.26%
BenchmarkRegexpMatchMedium_1K 114568 114763 +0.17%
BenchmarkRegexpMatchHard_1K 168977 169244 +0.16%
BenchmarkRevcomp 935294971 914060918 -2.27%
BenchmarkTemplate 145917123 148186096 +1.55%
Minux previous reported larger variations, but these were caused by
run-to-run noise, not repeatable slowdowns.
Actual code changes by Minux.
I only did the docs and the benchmarking.
LGTM=dvyukov, iant, minux
R=minux, josharian, iant, dave, bradfitz, dvyukov
CC=golang-codereviews
https://golang.org/cl/109050043
Also make it clear this is not a complete description of all features.
Fixes#7790.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/88300044
