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This CL marks some darwin assembly functions as NOFRAME to avoid relying
on the implicit amd64 NOFRAME heuristic, where NOSPLIT functions
without stack were also marked as NOFRAME.
Change-Id: I797f3909bcf7f7aad304e4ede820c884231e54f6
Reviewed-on: https://go-review.googlesource.com/c/go/+/460235
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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This CL marks non-leaf nosplit assembly functions as NOFRAME to avoid
relying on the implicit amd64 NOFRAME heuristic, where NOSPLIT functions
without stack were also marked as NOFRAME.
Updates #57302
Updates #40044
Change-Id: Ia4d26f8420dcf2b54528969ffbf40a73f1315d61
Reviewed-on: https://go-review.googlesource.com/c/go/+/459395
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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This CL redesign how we get the TLS pointer on windows/i386.
It applies the same changes as done in CL 431775 for windows/amd64.
We were previously reading it from the [TEB] arbitrary data slot,
located at 0x14(FS), which can only hold 1 TLS pointer.
With this CL, we will read the TLS pointer from the TEB TLS slot array,
located at 0xE10(GS). The TLS slot array can hold multiple
TLS pointers, up to 64, so multiple Go runtimes running on the
same thread can coexists with different TLS.
Each new TLS slot has to be allocated via [TlsAlloc],
which returns the slot index. This index can then be used to get the
slot offset from GS with the following formula: 0xE10 + index*4.
The slot index is fixed per Go runtime, so we can store it
in runtime.tls_g and use it latter on to read/update the TLS pointer.
Loading the TLS pointer requires the following asm instructions:
MOVQ runtime.tls_g, AX
MOVQ AX(FS), AX
Notice that this approach will now be implemented in all the supported
windows arches.
[TEB]: https://en.wikipedia.org/wiki/Win32_Thread_Information_Block
[TlsAlloc]: https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-tlsalloc
Change-Id: If4550b0d44694ee6480d4093b851f4991a088b32
Reviewed-on: https://go-review.googlesource.com/c/go/+/454675
Reviewed-by: Michael Pratt <mpratt@google.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
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testenv.Command sets a default timeout based on the test's deadline
and sends SIGQUIT (where supported) in case of a hang.
Change-Id: Ica1a9985f9abb1935434367c9c8ba28fc50f331d
Reviewed-on: https://go-review.googlesource.com/c/go/+/450699
Auto-Submit: Bryan Mills <bcmills@google.com>
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Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
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This CL redesign how we get the TLS pointer on windows/amd64.
We were previously reading it from the [TEB] arbitrary data slot,
located at 0x28(GS), which can only hold 1 TLS pointer.
With this CL, we will read the TLS pointer from the TEB TLS slot array,
located at 0x1480(GS). The TLS slot array can hold multiple
TLS pointers, up to 64, so multiple Go runtimes running on the
same thread can coexists with different TLS.
Each new TLS slot has to be allocated via [TlsAlloc],
which returns the slot index. This index can then be used to get the
slot offset from GS with the following formula: 0x1480 + index*8
The slot index is fixed per Go runtime, so we can store it
in runtime.tls_g and use it latter on to read/update the TLS pointer.
Loading the TLS pointer requires the following asm instructions:
MOVQ runtime.tls_g, AX
MOVQ AX(GS), AX
Notice that this approach is also implemented on windows/arm64.
[TEB]: https://en.wikipedia.org/wiki/Win32_Thread_Information_Block
[TlsAlloc]: https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-tlsalloc
Updates #22192
Change-Id: Idea7119fd76a3cd083979a4d57ed64b552fa101b
Reviewed-on: https://go-review.googlesource.com/c/go/+/431775
Reviewed-by: Cherry Mui <cherryyz@google.com>
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Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
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Change-Id: Ia5a090953d324f0f8aa9c1808c88125ad5eb6f98
Reviewed-on: https://go-review.googlesource.com/c/go/+/448955
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
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Change-Id: I4b596b252c1785b13c4a166e9ef5f4ae812cd1bc
Reviewed-on: https://go-review.googlesource.com/c/go/+/436704
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
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Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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For #45557
Change-Id: I56824135d86452603dd4ed4bab0e24c201bb0683
Reviewed-on: https://go-review.googlesource.com/c/go/+/426257
Run-TryBot: Ian Lance Taylor <iant@google.com>
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Reviewed-by: Ian Lance Taylor <iant@google.com>
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Performance is kind of hard to exactly quantify.
One big difference between jump tables and the old binary search
scheme is that there's only 1 branch statement instead of O(n) of
them. That can be both a blessing and a curse, and can make evaluating
jump tables very hard to do.
The single branch can become a choke point for the hardware branch
predictor. A branch table jump must fit all of its state in a single
branch predictor entry (technically, a branch target predictor entry).
With binary search that predictor state can be spread among lots of
entries. In cases where the case selection is repetitive and thus
predictable, binary search can perform better.
The big win for a jump table is that it doesn't consume so much of the
branch predictor's resources. But that benefit is essentially never
observed in microbenchmarks, because the branch predictor can easily
keep state for all the binary search branches in a microbenchmark. So
that benefit is really hard to measure.
So predictable switch microbenchmarks are ~useless - they will almost
always favor the binary search scheme. Fully unpredictable switch
microbenchmarks are better, as they aren't lying to us quite so
much. In a perfectly unpredictable situation, a jump table will expect
to incur 1-1/N branch mispredicts, where a binary search would incur
lg(N)/2 of them. That makes the crossover point at about N=4. But of
course switches in real programs are seldom fully unpredictable, so
we'll use a higher crossover point.
Beyond the branch predictor, jump tables tend to execute more
instructions per switch but have no additional instructions per case,
which also argues for a larger crossover.
As far as code size goes, with this CL cmd/go has a slightly smaller
code segment and a slightly larger overall size (from the jump tables
themselves which live in the data segment).
This is a case where some FDO (feedback-directed optimization) would
be really nice to have. #28262
Some large-program benchmarks might help make the case for this
CL. Especially if we can turn on branch mispredict counters so we can
see how much using jump tables can free up branch prediction resources
that can be gainfully used elsewhere in the program.
name old time/op new time/op delta
Switch8Predictable 1.89ns ± 2% 1.27ns ± 3% -32.58% (p=0.000 n=9+10)
Switch8Unpredictable 9.33ns ± 1% 7.50ns ± 1% -19.60% (p=0.000 n=10+9)
Switch32Predictable 2.20ns ± 2% 1.64ns ± 1% -25.39% (p=0.000 n=10+9)
Switch32Unpredictable 10.0ns ± 2% 7.6ns ± 2% -24.04% (p=0.000 n=10+10)
Fixes #5496
Update #34381
Change-Id: I3ff56011d02be53f605ca5fd3fb96b905517c34f
Reviewed-on: https://go-review.googlesource.com/c/go/+/357330
Run-TryBot: Keith Randall <khr@golang.org>
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Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@google.com>
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[This CL is part of a sequence implementing the proposal #51082.
The design doc is at https://go.dev/s/godocfmt-design.]
Run the updated gofmt, which reformats doc comments,
on the main repository. Vendored files are excluded.
For #51082.
Change-Id: I7332f099b60f716295fb34719c98c04eb1a85407
Reviewed-on: https://go-review.googlesource.com/c/go/+/384268
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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A future change to gofmt will rewrite
// Doc comment.
//
func f()
to
// Doc comment.
func f()
Apply that change preemptively to all doc comments.
For #51082.
Change-Id: I4023e16cfb0729b64a8590f071cd92f17343081d
Reviewed-on: https://go-review.googlesource.com/c/go/+/384259
Trust: Russ Cox <rsc@golang.org>
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Fixes: #49716
Change-Id: I7ed73f874c2ee1ee3f31c9c4428ed484167ca803
Reviewed-on: https://go-review.googlesource.com/c/go/+/366094
Reviewed-by: Cherry Mui <cherryyz@google.com>
Trust: Heschi Kreinick <heschi@google.com>
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This adds a debugging hook for optionally calling a "maymorestack"
function in the prologue of any function that might call morestack
(whether it does at run time or not). The maymorestack function will
let us improve lock checking and add debugging modes that stress
function preemption and stack growth.
Passes toolstash-check -all (except on js/wasm, where toolstash
appears to be broken)
Fixes #48297.
Change-Id: I27197947482b329af75dafb9971fc0d3a52eaf31
Reviewed-on: https://go-review.googlesource.com/c/go/+/359795
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
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The compiler refuses to do spectre mitigation on 386, but the
assembler doesn't. Fix that.
Fixes #49006
Change-Id: I887b6f7ed7523a47f463706f06ca4c2c6e828b6b
Reviewed-on: https://go-review.googlesource.com/c/go/+/356190
Trust: Keith Randall <khr@golang.org>
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The double suffix doesn't seem to serve any purpose, and we can keep
the old spelling as a backwards compatible alias in cmd/asm.
Change-Id: I3f01fc7249fb093ac1b25bd75c1cb9f39b8f62a9
Reviewed-on: https://go-review.googlesource.com/c/go/+/354700
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Currently, deferreturn runs deferred functions by backing up its
return PC to the deferreturn call, and then effectively tail-calling
the deferred function (via jmpdefer). The effect of this is that the
deferred function appears to be called directly from the deferee, and
when it returns, the deferee calls deferreturn again so it can run the
next deferred function if necessary.
This unusual flow control leads to a large number of special cases and
complications all over the tool chain.
This used to be necessary because deferreturn copied the deferred
function's argument frame directly into its caller's frame and then
had to invoke that call as if it had been called from its caller's
frame so it could access it arguments. But now that we've simplified
defer processing so the runtime only deals with argument-less
closures, this approach is no longer necessary.
This CL simplifies all of this by making deferreturn simply call
deferred functions in a loop.
This eliminates the need for jmpdefer, so we can delete a bunch of
per-architecture assembly code.
This eliminates several special cases on Wasm, since it couldn't
support these calling shenanigans directly and thus had to simulate
the loop a different way. Now Wasm can largely work the way the other
platforms do.
This eliminates the per-architecture Ginsnopdefer operation. On PPC64,
this was necessary to reload the TOC pointer after the tail call
(since TOC pointers in general make tail calls impossible). The tail
call is gone, and in the case where we do force a jump to the
deferreturn call when recovering from an open-coded defer, we go
through gogo (via runtime.recovery), which handles the TOC. On other
platforms, we needed a NOP so traceback didn't get confused by seeing
the return to the CALL instruction, rather than the usual return to
the instruction following the CALL instruction. Now we don't inject a
return to the CALL instruction at all, so this NOP is also
unnecessary.
The one potential effect of this is that deferreturn could now appear
in stack traces from deferred functions. However, this could already
happen from open-coded defers, so we've long since marked deferreturn
as a "wrapper" so it gets elided not only from printed stack traces,
but from runtime.Callers*.
This is a retry of CL 337652 because we had to back out its parent.
There are no changes in this version.
Change-Id: I3f54b7fec1d7ccac71cc6cf6835c6a46b7e5fb6c
Reviewed-on: https://go-review.googlesource.com/c/go/+/339397
Trust: Austin Clements <austin@google.com>
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Reviewed-by: Cherry Mui <cherryyz@google.com>
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replace jmpdefer with a loop"
This reverts CL 227652.
I'm reverting CL 337651 and this builds on top of it.
Change-Id: I03ce363be44c2a3defff2e43e7b1aad83386820d
Reviewed-on: https://go-review.googlesource.com/c/go/+/338709
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
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Reviewed-by: Cherry Mui <cherryyz@google.com>
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Currently, deferreturn runs deferred functions by backing up its
return PC to the deferreturn call, and then effectively tail-calling
the deferred function (via jmpdefer). The effect of this is that the
deferred function appears to be called directly from the deferee, and
when it returns, the deferee calls deferreturn again so it can run the
next deferred function if necessary.
This unusual flow control leads to a large number of special cases and
complications all over the tool chain.
This used to be necessary because deferreturn copied the deferred
function's argument frame directly into its caller's frame and then
had to invoke that call as if it had been called from its caller's
frame so it could access it arguments. But now that we've simplified
defer processing so the runtime only deals with argument-less
closures, this approach is no longer necessary.
This CL simplifies all of this by making deferreturn simply call
deferred functions in a loop.
This eliminates the need for jmpdefer, so we can delete a bunch of
per-architecture assembly code.
This eliminates several special cases on Wasm, since it couldn't
support these calling shenanigans directly and thus had to simulate
the loop a different way. Now Wasm can largely work the way the other
platforms do.
This eliminates the per-architecture Ginsnopdefer operation. On PPC64,
this was necessary to reload the TOC pointer after the tail call
(since TOC pointers in general make tail calls impossible). The tail
call is gone, and in the case where we do force a jump to the
deferreturn call when recovering from an open-coded defer, we go
through gogo (via runtime.recovery), which handles the TOC. On other
platforms, we needed a NOP so traceback didn't get confused by seeing
the return to the CALL instruction, rather than the usual return to
the instruction following the CALL instruction. Now we don't inject a
return to the CALL instruction at all, so this NOP is also
unnecessary.
The one potential effect of this is that deferreturn could now appear
in stack traces from deferred functions. However, this could already
happen from open-coded defers, so we've long since marked deferreturn
as a "wrapper" so it gets elided not only from printed stack traces,
but from runtime.Callers*.
Change-Id: Ie9f700cd3fb774f498c9edce363772a868407bf7
Reviewed-on: https://go-review.googlesource.com/c/go/+/337652
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
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Reviewed-by: Cherry Mui <cherryyz@google.com>
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Always enable regabig on AMD64, which enables the G register and
the X15 zero register. Remove the fallback path.
Also remove the regabig GOEXPERIMENT. On AMD64 it is always
enabled (this CL). Other architectures already have a G register,
except for 386, where there are too few registers and it is
unlikely that we will reserve one. (If we really do, we can just
add a new experiment).
Change-Id: I229cac0060f48fe58c9fdaabd38d6fa16b8a0855
Reviewed-on: https://go-review.googlesource.com/c/go/+/327272
Trust: Cherry Mui <cherryyz@google.com>
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Reviewed-by: David Chase <drchase@google.com>
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The go/build package needs access to this configuration,
so move it into a new package available to the standard library.
Change-Id: I868a94148b52350c76116451f4ad9191246adcff
Reviewed-on: https://go-review.googlesource.com/c/go/+/310731
Trust: Russ Cox <rsc@golang.org>
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Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
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There are several assembly functions that transition from the Windows
ABI to the Go ABI. These all need to save all registers that are
callee-save in the Windows ABI and caller-save in the Go ABI and
prepare the register state for Go. However, they all do this slightly
differently and most of them don't save the necessary XMM registers
for this transition (which could corrupt them in the C caller).
Furthermore, now that we have a carefully specified Go ABI, it's clear
that none of these actually get all of the details 100% right.
So, unify this code into two macros in a shared header in
runtime/cgo/abi_amd64.h that handle all necessary registers and setup
and use these macros everywhere on Windows that handles transitions
from C to Go.
Change-Id: I62f41345a507aad1ca383814ac8b7e2a9ffb821e
Reviewed-on: https://go-review.googlesource.com/c/go/+/309769
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
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Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
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Currently, there are Wrapper and ABIWrapper attributes. Wrapper
is set when compiler generates an wrapper function (e.g. method
wrapper). ABIWrapper is set when compiler generates an ABI
wrapper. It also sets Wrapper flag for ABI wrappers.
Currently, they have the following meanings:
- Wrapper flag hides the frame from (normal) traceback.
- Wrapper flag enables special panic+recover adjustment, so it
can correctly recover when a wrapper function is deferred.
- ABIWrapper flag disables the panic+recover adjustment, because
we never defer an ABI wrapper that can recover.
This CL changes them to:
- Both Wrapper and ABIWrapper flags hide the frame from (normal)
traceback. (Setting one is enough.)
- Wrapper flag enables special panic+recover adjustment.
ABIWrapper flag no longer has effect on this.
This makes it clearer if we do want an ABI wrapper that also does
the panic+recover adjustment. In the old mechanism we'd have to
unset ABIWrapper flag, even if the function is actually an ABI
wrapper. In the new mechanism we just need to set both ABIWrapper
and Wrapper flags.
Updates #40724.
Change-Id: I7fbc83f85d23676dc94db51dfda63dcacdf1fc19
Reviewed-on: https://go-review.googlesource.com/c/go/+/307235
Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Austin Clements <austin@google.com>
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For stack frames larger than StackBig, the stack split prologue needs
to guard against potential wraparound. Currently, it carefully
arranges to avoid underflow, but this is complicated and requires a
special check for StackPreempt. StackPreempt is no longer the only
stack poison value, so this check will incorrectly succeed if the
stack bound is poisoned with any other value.
This CL simplifies the logic of the check, reduces its length, and
accounts for any possible poison value by directly checking for
underflow.
Change-Id: I917a313102d6a21895ef7c4b0f304fb84b292c81
Reviewed-on: https://go-review.googlesource.com/c/go/+/307010
Trust: Austin Clements <austin@google.com>
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Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
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There are a few remaining places in obj6 where we hard-code
safe-on-entry registers. Fix those to use the consts.
For #40724.
Change-Id: Ie640521aa67d6c99bc057553dc122160049c6edc
Reviewed-on: https://go-review.googlesource.com/c/go/+/307009
Trust: Austin Clements <austin@google.com>
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Currently the prologue generated for WRAPPER assembly functions uses BX
and DI, but these are argument registers in the register-based calling
convention. Thus, these end up being clobbered when we want to have an
ABIInternal assembly function.
Define REGENTRYTMP0 and REGENTRYTMP1, aliases for the dedicated function
entry scratch registers R12 and R13, and use those instead.
For #40724.
Change-Id: Ica78c4ccc67a757359900a66b56ef28c83d88b3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/303314
Trust: Michael Knyszek <mknyszek@google.com>
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This separates GOEXPERIMENT=regabi into five sub-experiments:
regabiwrappers, regabig, regabireflect, regabidefer, and regabiargs.
Setting GOEXPERIMENT=regabi now implies the working subset of these
(currently, regabiwrappers, regabig, and regabireflect).
This simplifies testing, helps derisk the register ABI project,
and will also help with performance comparisons.
This replaces the -abiwrap flag to the compiler and linker with
the regabiwrappers experiment.
As part of this, regabiargs now enables registers for all calls
in the compiler. Previously, this was statically disabled in
regabiEnabledForAllCompilation, but now that we can control it
independently, this isn't necessary.
For #40724.
Change-Id: I5171e60cda6789031f2ef034cc2e7c5d62459122
Reviewed-on: https://go-review.googlesource.com/c/go/+/302070
Trust: Austin Clements <austin@google.com>
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Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>
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The assember uses R15 as scratch space when assembling global variable
references in dynamically linked code. If the assembly code uses the
clobbered value of R15, report an error. The user is probably expecting
some other value in that register.
Getting rid of the R15 use isn't very practical (we could save a
register to a field in the G maybe, but that gets cumbersome).
Fixes #43661
Change-Id: I43f848a3d8b8a28931ec733386b85e6e9a42d8ff
Reviewed-on: https://go-review.googlesource.com/c/go/+/283474
Trust: Keith Randall <khr@golang.org>
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ABI info producer and consumer had different ideas for register
order for parameters.
Includes a test, includes improvements to debugging output.
Updates #44816.
Change-Id: I4812976f7a6c08d6fc02aac1ec0544b1f141cca6
Reviewed-on: https://go-review.googlesource.com/c/go/+/299570
Trust: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
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Morestack works for non-pointer register parameters
Within a function body, pointer-typed parameters are correctly
tracked.
Results still not hooked up.
For #40724.
Change-Id: Icaee0b51d0da54af983662d945d939b756088746
Reviewed-on: https://go-review.googlesource.com/c/go/+/294410
Trust: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
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Change-Id: Ib689e5793d9cb372e759c4f34af71f004010c822
GitHub-Last-Rev: d63798388e5dcccb984689b0ae39b87453b97393
GitHub-Pull-Request: golang/go#44259
Reviewed-on: https://go-review.googlesource.com/c/go/+/291949
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Robert Griesemer <gri@golang.org>
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The runtime traceback code has its own definition of which functions
mark the top frame of a stack, separate from the TOPFRAME bits that
exist in the assembly and are passed along in DWARF information.
It's error-prone and redundant to have two different sources of truth.
This CL provides the actual TOPFRAME bits to the runtime, so that
the runtime can use those bits instead of reinventing its own category.
This CL also adds a new bit, SPWRITE, which marks functions that
write directly to SP (anything but adding and subtracting constants).
Such functions must stop a traceback, because the traceback has no
way to rederive the SP on entry. Again, the runtime has its own definition
which is mostly correct, but also missing some functions. During ordinary
goroutine context switches, such functions do not appear on the stack,
so the incompleteness in the runtime usually doesn't matter.
But profiling signals can arrive at any moment, and the runtime may
crash during traceback if it attempts to unwind an SP-writing frame
and gets out-of-sync with the actual stack. The runtime contains code
to try to detect likely candidates but again it is incomplete.
Deriving the SPWRITE bit automatically from the actual assembly code
provides the complete truth, and passing it to the runtime lets the
runtime use it.
This CL is part of a stack adding windows/arm64
support (#36439), intended to land in the Go 1.17 cycle.
This CL is, however, not windows/arm64-specific.
It is cleanup meant to make the port (and future ports) easier.
Change-Id: I227f53b23ac5b3dabfcc5e8ee3f00df4e113cf58
Reviewed-on: https://go-review.googlesource.com/c/go/+/288800
Trust: Russ Cox <rsc@golang.org>
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
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In ABIInternal context, we can directly use the g register for
stack bounds check.
Change-Id: I8b1073a3343984a6cd76cf5734ddc4a8cd5dc73f
Reviewed-on: https://go-review.googlesource.com/c/go/+/289711
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
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Define g register as R14 on AMD64. It is not used now, but will
be in later CLs.
The name "R14" is still recognized.
Change-Id: I9a066b15bf1051113db8c6640605e350cea397b9
Reviewed-on: https://go-review.googlesource.com/c/go/+/289195
Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
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morestack calls
This is a selected copy from the register ABI experiment CL, focused
on the files and data structures that handle spilling around morestack.
Unnecessary code from the experiment was removed, other code was adapted.
Would it make sense to leave comments in the experiment as pieces are
brought over?
Experiment CL (for comparison purposes)
https://go-review.googlesource.com/c/go/+/28832
Change-Id: I92136f070351d4fcca1407b52ecf9b80898fed95
Reviewed-on: https://go-review.googlesource.com/c/go/+/279520
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
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Add compiler support for emitting ABI wrappers by creating real IR as
opposed to introducing ABI aliases. At the moment these are "no-op"
wrappers in the sense that they make a simple call (using the existing
ABI) to their target. The assumption here is that once late call
expansion can handle both ABI0 and the "new" ABIInternal (register
version), it can expand the call to do the right thing.
Note that the runtime contains functions that do not strictly follow
the rules of the current Go ABI0; this has been handled in most cases
by treating these as ABIInternal instead (these changes have been made
in previous patches).
Generation of ABI wrappers (as opposed to ABI aliases) is currently
gated by GOEXPERIMENT=regabi -- wrapper generation is on by default if
GOEXPERIMENT=regabi is set and off otherwise (but can be turned on
using "-gcflags=all=-abiwrap -ldflags=-abiwrap"). Wrapper generation
currently only workd on AMD64; explicitly enabling wrapper for other
architectures (via the command line) is not supported.
Also in this patch are a few other command line options for debugging
(tracing and/or limiting wrapper creation). These will presumably go
away at some point.
Updates #27539, #40724.
Change-Id: I1ee3226fc15a3c32ca2087b8ef8e41dbe6df4a75
Reviewed-on: https://go-review.googlesource.com/c/go/+/270863
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Trust: Than McIntosh <thanm@google.com>
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Always do aligned jumps now.
Change-Id: If68a16fe93c9173c83323a9063465c9bd166eeb8
Reviewed-on: https://go-review.googlesource.com/c/go/+/266857
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
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[This is a roll-forward of CL 262319, with a fix for some Darwin test
failures].
Change the definitions of selected runtime assembly routines
from ABI0 (the default) to ABIInternal. The ABIInternal def is
intended to indicate that these functions don't follow the existing Go
runtime ABI. In addition, convert the assembly reference to
runtime.main (from runtime.mainPC) to ABIInternal. Finally, for
functions such as "runtime.duffzero" that are called directly from
generated code, make sure that the compiler looks up the correct
ABI version.
This is intended to support the register abi work, however these
changes should not have any issues even when GOEXPERIMENT=regabi is
not in effect.
Updates #27539, #40724.
Change-Id: Idf507f1c06176073563845239e1a54dad51a9ea9
Reviewed-on: https://go-review.googlesource.com/c/go/+/266638
Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
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This patch adds support for CASx and CASPx atomic instructions.
go syntax gnu syntax
CASD Rs, (Rn|RSP), Rt => cas Xs, Xt, (Xn|SP)
CASALW Rs, (Rn|RSP), Rt => casal Ws, Wt, (Xn|SP)
CASPD (Rs, Rs+1), (Rn|RSP), (Rt, Rt+1) => casp Xs, Xs+1, Xt, Xt+1, (Xn|SP)
CASPW (Rs, Rs+1), (Rn|RSP), (Rt, Rt+1) => casp Ws, Ws+1, Wt, Wt+1, (Xn|SP)
This patch changes the type of prog.RestArgs from "[]Addr" to
"[]struct{Addr, Pos}", Pos is a enum, indicating the position of
the operand.
This patch also adds test cases.
Change-Id: Ib971cfda7890b7aa895d17bab22dea326c7fcaa4
Reviewed-on: https://go-review.googlesource.com/c/go/+/233277
Trust: fannie zhang <Fannie.Zhang@arm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
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This creates space for a different kind of extension field
in LSym without making the struct any larger.
(There are many LSym, so we care about keeping the struct small.)
Change-Id: Ib16edb9e15f54c2a7351c8b875e19684058711e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/243943
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
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The linker prunes methods that are not directly reachable if the
receiver type is never converted to interface. Currently, this
"never" is too strong: it is invalidated even if the interface
conversion is in an unreachable function. This CL improves it by
only considering interface conversions in reachable code. To do
that, we introduce a marker relocation R_USEIFACE, which marks
the target symbol as UsedInIface if the source symbol is reached.
binary size before after
cmd/compile 18897528 18887400
cmd/go 13607372 13470652
Change-Id: I66c6b69eeff9ae02d84d2e6f2bc7f1b29dd53910
Reviewed-on: https://go-review.googlesource.com/c/go/+/256797
Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
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We currently use two fields to store the targets of branches.
Some phases use p.To.Val, some use p.Pcond. Rewrite so that
every branch instruction uses p.To.Val.
p.From.Val is also used in rare instances.
Introduce a Pool link for use by arm/arm64, instead of
repurposing Pcond.
This is a cleanup CL in preparation for some stack frame CLs.
Change-Id: If8239177e4b1ea2bccd0608eb39553d23210d405
Reviewed-on: https://go-review.googlesource.com/c/go/+/251437
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
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This reverts CL 243318.
Reason for revert: Seems to be crashing some builders.
Change-Id: I2ffc59bc5535be60b884b281c8d0eff4647dc756
Reviewed-on: https://go-review.googlesource.com/c/go/+/251169
Reviewed-by: Bryan C. Mills <bcmills@google.com>
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We currently use two fields to store the targets of branches.
Some phases use p.To.Val, some use p.Pcond. Rewrite so that
every branch instruction uses p.To.Val.
p.From.Val is also used in rare instances.
Introduce a Pool link for use by arm/arm64, instead of
repurposing Pcond.
This is a cleanup CL in preparation for some stack frame CLs.
Change-Id: I9055bf0a1d986aff421e47951a1dedc301c846f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/243318
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
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I think they are no longer experimental status. Might as well promote
them to permanent.
Change-Id: Id1259601b3dd2061dd60df86ee48080bfb575d2f
Reviewed-on: https://go-review.googlesource.com/c/go/+/249857
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
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Generated using:
perl -i -npe 's#inferno-os/src/default#inferno-os/src/master#' $(git grep -l "inferno-os/src/default" | grep -v vendor)
Change-Id: I4b6443bd09a8ea4c8aaeb40a1c73520d1f7ca648
Reviewed-on: https://go-review.googlesource.com/c/go/+/235821
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>
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On some architectures, for async preemption the injected call
needs to clobber a register (usually REGTMP) in order to return
to the preempted function. As a consequence, the PC ranges where
REGTMP is live are not preemptible.
The uses of REGTMP are usually generated by the assembler, where
it needs to load or materialize a large constant or offset that
doesn't fit into the instruction. In those cases, REGTMP is not
live at the start of the instruction sequence. Instead of giving
up preemption in those cases, we could preempt it and restart the
sequence when resuming the execution. Basically, this is like
reissuing an interrupted instruction, except that here the
"instruction" is a Prog that consists of multiple machine
instructions. For this to work, we need to generate PC data to
mark the start of the Prog.
Currently this is only done for ARM64.
TODO: the split-stack function prologue is currently not async
preemptible. We could use this mechanism, preempt it and restart
at the function entry.
Change-Id: I37cb282f8e606e7ab6f67b3edfdc6063097b4bd1
Reviewed-on: https://go-review.googlesource.com/c/go/+/208126
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
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This commit adds a new option to the x86 assembler. If the
GOAMD64 environment variable is set to alignedjumps (the
default) and we're doing a 64 bit build, the assembler will
make sure that neither stand alone nor macro-fused jumps will
end on or cross 32 byte boundaries. To achieve this, functions
are aligned on 32 byte boundaries, rather than 16 bytes, and
jump instructions are padded to ensure that they do not
cross or end on 32 byte boundaries. Jumps are padded
by adding a NOP instruction of the appropriate length before
the jump.
The commit is likely to result in larger binary sizes when
GOAMD64=alignedjumps. On the binaries tested so far, an
increase of between 1.4% and 1.5% has been observed.
Updates #35881
Co-authored-by: David Chase <drchase@google.com>
Change-Id: Ief0722300bc3f987098e4fd92b22b14ad6281d91
Reviewed-on: https://go-review.googlesource.com/c/go/+/219357
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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This commit extends the -spectre flag to cmd/asm and adds
a new Spectre mitigation mode "ret", which enables the use
of retpolines.
Retpolines prevent speculation about the target of an indirect
jump or call and are described in more detail here:
https://support.google.com/faqs/answer/7625886
Change-Id: I4f2cb982fa94e44d91e49bd98974fd125619c93a
Reviewed-on: https://go-review.googlesource.com/c/go/+/222661
Reviewed-by: Keith Randall <khr@golang.org>
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When there are both a synchronous preemption request (by
clobbering the stack guard) and an asynchronous one (by signal),
the running goroutine may observe the synchronous request first
in stack bounds check, and go to the path of calling morestack.
If the preemption signal arrives at this point before the call to
morestack, the goroutine will be asynchronously preempted,
entering the scheduler. When it is resumed, the scheduler clears
the preemption request, unclobbers the stack guard. But the
resumed goroutine will still call morestack, as it is already on
its way. morestack will, as there is no preemption request,
double the stack unnecessarily. If this happens multiple times,
the stack may grow too big, although only a small amount is
actually used.
To fix this, we mark the stack bounds check and the call to
morestack async-nonpreemptible, starting after the memory
instruction (mostly a load, on x86 CMP with memory).
Not done for Wasm as it does not support async preemption.
Fixes #35470.
Change-Id: Ibd7f3d935a3649b80f47539116ec9b9556680cf2
Reviewed-on: https://go-review.googlesource.com/c/go/+/207350
Reviewed-by: David Chase <drchase@google.com>
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The 2-instruction TLS access sequence
MOVQ TLS, BX
MOVQ 0(BX)(TLS*1), BX
is not async preemptible, as if it is preempted and resumed on a
different thread, the TLS address may become invalid.
May fix #35349. (This is a rare failure and I haven't been able
to reproduce it.)
Change-Id: Ie1a366fd0d7d73627dc62ee2de01c0aa09365f2b
Reviewed-on: https://go-review.googlesource.com/c/go/+/206903
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>
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