[This is a partial roll-forward of CL 553055, the main change here
is that the stack slot overlap operation is flagged off by default
(can be enabled by hand with -gcflags=-d=mergelocals=1) ]
Preliminary compiler support for merging/overlapping stack slots of
local variables whose access patterns are disjoint.
This patch includes changes in AllocFrame to do the actual
merging/overlapping based on information returned from a new
liveness.MergeLocals helper. The MergeLocals helper identifies
candidates by looking for sets of AUTO variables that either A) have
the same size and GC shape (if types contain pointers), or B) have the
same size (but potentially different types as long as those types have
no pointers). Variables must be greater than (3*types.PtrSize) in size
to be considered for merging.
After forming candidates, MergeLocals collects variables into "can be
overlapped" equivalence classes or partitions; this process is driven
by an additional liveness analysis pass. Ideally it would be nice to
move the existing stackmap liveness pass up before AllocFrame
and "widen" it to include merge candidates so that we can do just a
single liveness as opposed to two passes, however this may be difficult
given that the merge-locals liveness has to take into account
writes corresponding to dead stores.
This patch also required a change to the way ssa.OpVarDef pseudo-ops
are generated; prior to this point they would only be created for
variables whose type included pointers; if stack slot merging is
enabled then the ssagen code creates OpVarDef ops for all auto vars
that are merge candidates.
Note that some temporaries created late in the compilation process
(e.g. during ssa backend) are difficult to reason about, especially in
cases where we take the address of a temp and pass it to the runtime.
For the time being we mark most of the vars created post-ssagen as
"not a merge candidate".
Stack slot merging for locals/autos is enabled by default if "-N" is
not in effect, and can be disabled via "-gcflags=-d=mergelocals=0".
Fixmes/todos/restrictions:
- try lowering size restrictions
- re-evaluate the various skips that happen in SSA-created autotmps
Updates #62737.
Updates #65532.
Updates #65495.
Change-Id: Ifda26bc48cde5667de245c8a9671b3f0a30bb45d
Reviewed-on: https://go-review.googlesource.com/c/go/+/575415
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This reverts CL 553055.
Reason for revert: causes crypto/ecdsa failures on linux ppc64/s390x builders
Change-Id: I9266b030693a5b6b1e667a009de89d613755b048
Reviewed-on: https://go-review.googlesource.com/c/go/+/575236
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Preliminary compiler support for merging/overlapping stack
slots of local variables whose access patterns are disjoint.
This patch includes changes in AllocFrame to do the actual
merging/overlapping based on information returned from a new
liveness.MergeLocals helper. The MergeLocals helper identifies
candidates by looking for sets of AUTO variables that either A) have
the same size and GC shape (if types contain pointers), or B) have the
same size (but potentially different types as long as those types have
no pointers). Variables must be greater than (3*types.PtrSize) in size
to be considered for merging.
After forming candidates, MergeLocals collects variables into "can be
overlapped" equivalence classes or partitions; this process is driven
by an additional liveness analysis pass. Ideally it would be nice to
move the existing stackmap liveness pass up before AllocFrame
and "widen" it to include merge candidates so that we can do just a
single liveness as opposed to two passes, however this may be difficult
given that the merge-locals liveness has to take into account
writes corresponding to dead stores.
This patch also required a change to the way ssa.OpVarDef pseudo-ops
are generated; prior to this point they would only be created for
variables whose type included pointers; if stack slot merging is
enabled then the ssagen code creates OpVarDef ops for all auto vars
that are merge candidates.
Note that some temporaries created late in the compilation process
(e.g. during ssa backend) are difficult to reason about, especially in
cases where we take the address of a temp and pass it to the runtime.
For the time being we mark most of the vars created post-ssagen as
"not a merge candidate".
Stack slot merging for locals/autos is enabled by default if "-N" is
not in effect, and can be disabled via "-gcflags=-d=mergelocals=0".
Fixmes/todos/restrictions:
- try lowering size restrictions
- re-evaluate the various skips that happen in SSA-created autotmps
Fixes#62737.
Updates #65532.
Updates #65495.
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
Change-Id: Ibc22e8a76c87e47bc9fafe4959804d9ea923623d
Reviewed-on: https://go-review.googlesource.com/c/go/+/553055
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Change-Id: I38ba7cb0179ec9226a68629c53ea2d81fa19c059
GitHub-Last-Rev: a3d4fe2ac2
GitHub-Pull-Request: golang/go#66024
Reviewed-on: https://go-review.googlesource.com/c/go/+/568115
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>
Reviewed-by: qiulaidongfeng <2645477756@qq.com>
Auto-Submit: Robert Griesemer <gri@google.com>
This commit is aimed at improving the readability and consistency
of the code base. Extraneous newline characters were present after
some return statements, creating unnecessary separation in the code.
Fixes#64610
Change-Id: Ic1b05bf11761c4dff22691c2f1c3755f66d341f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/548316
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
When a PGO build fails or produces incorrect program, it is often
unclear what the problem is. Add pgo hash so we can bisect to
individual optimization decisions, which often helps debugging.
Related to #58153.
Change-Id: I651ffd9c53bad60f2f28c8ec2a90a3f532982712
Reviewed-on: https://go-review.googlesource.com/c/go/+/528400
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
If a hash match is "disabled" (!enabled) indicate that in the
output with DISABLED. This is helpful in ensuring that multiple
package-directed command-line flags have the intended behavior,
e.g.
```
go build -a \
-gcflags=all=-d=gossahash=vn \
-gcflags=runtime=-d=gossahash=vy \
std
```
Output looks like
[DISABLED] [bisect-match 0x11d0ee166d9d61b4]
or (w/ "v"-prefixed hashcode )
sort/slice.go:23:29 note [DISABLED] [bisect-match 0xa5252e1c1b85f2ec]
gossahash triggered sort/slice.go:23:29 note [DISABLED] 100001011111001011101100
Change-Id: I797e02b3132f9781d97bacd0dcd2e80af0035cd8
Reviewed-on: https://go-review.googlesource.com/c/go/+/497216
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
The FS form was only necessary for reliable hashes in tests,
and for that we can use -trimpath.
Another potential concern would be temporary work directory
names leaking into the names of files generated by cgo and the
like, but we already make sure to avoid those to ensure
reproducible builds: the compiler never sees those paths.
So the FS form is not necessary for that either.
Change-Id: Idae2c6acb22ab64dfb33bb053244d23fbe153830
Reviewed-on: https://go-review.googlesource.com/c/go/+/493737
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Using more of internal/bisect gives us more that will be deleted
from base/hashdebug.go when we have updated the tools that
need the old protocol. It is also cheaper: there is no allocation to
make a decision about whether to enable, and no locking unless
printing is needed.
Change-Id: I43ec398461205a1a9e988512a134ed6b3a3b1587
Reviewed-on: https://go-review.googlesource.com/c/go/+/493736
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
The call sites that cared all reversed inner-to-outer to outer-to-inner already.
The ones that didn't care left it alone. No one explicitly wanted inner-to-outer.
Also change to a callback-based interface, so that call sites aren't required
to accumulate the results in a slice (the main reason for that before was to
reverse the slice!).
There were three places where these lists were printed:
1. -d=ssa/genssa/dump, explicitly reversing to outer-to-inner
2. node dumps like -W, leaving the default inner-to-outer
3. file positions for HashDebugs, explicitly reversing to outer-to-inner
It makes no sense that (1) and (2) would differ. The reason they do is that
the code for (2) was too lazy to bother to fix it to be the right way.
Consider this program:
package p
func f() {
g()
}
func g() {
println()
}
Both before and after this change, the ssa dump for f looks like:
# x.go:3
00000 (3) TEXT <unlinkable>.f(SB), ABIInternal
00001 (3) FUNCDATA $0, gclocals·g2BeySu+wFnoycgXfElmcg==(SB)
00002 (3) FUNCDATA $1, gclocals·g2BeySu+wFnoycgXfElmcg==(SB)
v4 00003 (-4) XCHGL AX, AX
# x.go:4
# x.go:8
v5 00004 (+8) PCDATA $1, $0
v5 00005 (+8) CALL runtime.printlock(SB)
v7 00006 (-8) CALL runtime.printnl(SB)
v9 00007 (-8) CALL runtime.printunlock(SB)
# x.go:5
b2 00008 (5) RET
00009 (?) END
Note # x.go:4 (f) then # x.go:8 (g, called from f) between v4 and v5.
The -W node dumps used the opposite order:
before walk f
. AS2 Def tc(1) # x.go:4:3
. INLMARK # +x.go:4:3
. PRINTN tc(1) # x.go:8:9,x.go:4:3
. LABEL p..i0 # x.go:4:3
Now they match the ssa dump order, and they use spaces as separators,
to avoid potential problems with commas in some editors.
before walk f
. AS2 Def tc(1) # x.go:4:3
. INLMARK # +x.go:4:3
. PRINTN tc(1) # x.go:4:3 x.go:8:9
. LABEL p..i0 # x.go:4:3
I'm unaware of any argument for the old order other than it was easier
to compute without allocation. The new code uses recursion to reverse
the order without allocation.
Now that the callers get the results outer-to-inner, most don't need
any slices at all.
This change is particularly important for HashDebug, which had been
using a locked temporary slice to walk the inline stack without allocation.
Now the temporary slice is gone.
Change-Id: I5cb6d76b2f950db67b248acc928e47a0460569f9
Reviewed-on: https://go-review.googlesource.com/c/go/+/493735
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
CL 491875 introduces a new bisect command, which we plan to
document for use by end users to debug semantic changes in
the compiler and in GODEBUGs.
This CL adds bisect support to GODEBUGs, at least the ones
used via internal/godebug. Support for runtime-internal
GODEBUGs like panicnil will take a bit more work in followup CLs.
The new API in internal/bisect to support stack-based bisecting
should be easily reusable in non-GODEBUG settings as well,
once we finalize and export the API.
Change-Id: I6cf779c775329aceb3f3b2b2b2f221ce8a67deee
Reviewed-on: https://go-review.googlesource.com/c/go/+/491975
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
CL 491875 introduces a new bisect command, which we plan to
document for use by end users to debug semantic changes in
the compiler and in GODEBUGs.
This CL adapts the existing GOSSAHASH support, which bisect
is a revision of, to support the specific syntax and output used
by bisect as well.
A followup CL will remove the old GOSSAHASH syntax and output
once existing consumers of that interface have been updated.
Change-Id: I99c4af54bb82c91c74bd8b8282ded968e6316f56
Reviewed-on: https://go-review.googlesource.com/c/go/+/491895
Auto-Submit: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: David Chase <drchase@google.com>
HashDebugPos function/method included a parameter that was always
the same, and a variable in the same package as the hashdebug code.
So remove it.
(I wrote that code, there was no reason for it to be that way).
Also corrects a stale comment in the loopvar code.
Change-Id: Id3da69cfe6dadeb31d5de62fb76d15103a5d6152
Reviewed-on: https://go-review.googlesource.com/c/go/+/482816
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
The goal here is to enable a search that will locate all the instances
of a failure, not just the first one. This helps with searches for
loopvar-change breakage, FP differences from fused-multiply-add, and
allows certain semantics queries that can be implemented as compiler
changes (for example, where does integer overflow routinely occur?)
Change-Id: Ic28f1695d47e421c2089d1f3f7c4b40c56db970f
Reviewed-on: https://go-review.googlesource.com/c/go/+/481195
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Adds:
GOEXPERIMENT=loopvar (expected way of invoking)
-d=loopvar={-1,0,1,2,11,12} (for per-package control and/or logging)
-d=loopvarhash=... (for hash debugging)
loopvar=11,12 are for testing, benchmarking, and debugging.
If enabled,for loops of the form `for x,y := range thing`, if x and/or
y are addressed or captured by a closure, are transformed by renaming
x/y to a temporary and prepending an assignment to the body of the
loop x := tmp_x. This changes the loop semantics by making each
iteration's instance of x be distinct from the others (currently they
are all aliased, and when this matters, it is almost always a bug).
3-range with captured iteration variables are also transformed,
though it is a more complex transformation.
"Optimized" to do a simpler transformation for
3-clause for where the increment is empty.
(Prior optimization of address-taking under Return disabled, because
it was incorrect; returns can have loops for children. Restored in
a later CL.)
Includes support for -d=loopvarhash=<binary string> intended for use
with hash search and GOCOMPILEDEBUG=loopvarhash=<binary string>
(use `gossahash -e loopvarhash command-that-fails`).
Minor feature upgrades to hash-triggered features; clients can specify
that file-position hashes use only the most-inline position, and/or that
they use only the basenames of source files (not the full directory path).
Most-inlined is the right choice for debugging loop-iteration change
once the semantics are linked to the package across inlining; basename-only
makes it tractable to write tests (which, otherwise, depend on the full
pathname of the source file and thus vary).
Updates #57969.
Change-Id: I180a51a3f8d4173f6210c861f10de23de8a1b1db
Reviewed-on: https://go-review.googlesource.com/c/go/+/411904
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Modified the fmahash gc debug flag to use this, and modified the
test to check for a hash match that includes inlining. Also
made the test non-short to ensure portability.
Note fma.go has been enhanced into an FMA test that requires
two separate FMAs in order to "fail"; if either one is 2-rounding,
then it "passes". (It neither passes nor fails here; its role
is to demonstrate that the FMAs are correctly reported; the
enhanced failure mode was discovered while testing the search
tool.)
Change-Id: I4e328e3654f442d498eac982135420abb59c5434
Reviewed-on: https://go-review.googlesource.com/c/go/+/448358
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: David Chase <drchase@google.com>
Semicolon has bad copy-paste ergonomics; it requires quoting.
Slash is okay, and won't be a separator ever in debug strings
because it is already used in e.g. ssa/phase/debug=etc.
Change-Id: I493360e9282666eea1a342971a77df2ebd6c92ad
Reviewed-on: https://go-review.googlesource.com/c/go/+/447975
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This adds a -d debug flag "fmahash" for hashcode search for
floating point architecture-dependent problems. This variable has no
effect on architectures w/o fused-multiply-add.
This was rebased onto the GOSSAHASH renovation so that this could have
its own dedicated environment variable, and so that it would be
cheap (a nil check) to check it in the normal case.
Includes a basic test of the trigger plumbing.
Sample use (on arm64, ppc64le, s390x):
% GOCOMPILEDEBUG=fmahash=001110110 \
go build -o foo cmd/compile/internal/ssa/testdata/fma.go
fmahash triggered main.main:24 101111101101111001110110
GOFMAHASH triggered main.main:20 010111010000101110111011
1.0000000000000002 1.0000000000000004 -2.220446049250313e-16
exit status 1
The intended use is in conjunction with github.com/dr2chase/gossahash,
which will probably acquire a flag "-fma" to streamline its use. This
tool+use was inspired by an ad hoc use of this technique "in anger"
to debug this very problem. This is also a dry-run for using this
same technique to identify code sensitive to loop variable
lifetime/capture, should we make that change.
Example intended use, with current search tool (using old environment
variable), for a test example:
gossahash -e GOFMAHASH GOMAGIC=GOFMAHASH go run fma.go
Trying go args=[...], env=[GOFMAHASH=1 GOMAGIC=GOFMAHASH]
go failed (81 distinct triggers): exit status 1
Trying go args=[...], env=[GOFMAHASH=11 GOMAGIC=GOFMAHASH]
go failed (39 distinct triggers): exit status 1
Trying go args=[...], env=[GOFMAHASH=011 GOMAGIC=GOFMAHASH]
go failed (18 distinct triggers): exit status 1
Trying go args=[...], env=[GOFMAHASH=0011 GOMAGIC=GOFMAHASH]
Trying go args=[...], env=[GOFMAHASH=1011 GOMAGIC=GOFMAHASH]
...
Trying go args=[...], env=[GOFMAHASH=0110111011 GOMAGIC=GOFMAHASH]
Trying go args=[...], env=[GOFMAHASH=1110111011 GOMAGIC=GOFMAHASH]
go failed (2 distinct triggers): exit status 1
Trigger string is 'GOFMAHASH triggered math.qzero:427 111111101010011110111011', repeated 6 times
Trigger string is 'GOFMAHASH triggered main.main:20 010111010000101110111011', repeated 1 times
Trying go args=[...], env=[GOFMAHASH=01110111011 GOMAGIC=GOFMAHASH]
go failed (1 distinct triggers): exit status 1
Trigger string is 'GOFMAHASH triggered main.main:20 010111010000101110111011', repeated 1 times
Review GSHS_LAST_FAIL.0.log for failing run
FINISHED, suggest this command line for debugging:
GOSSAFUNC='main.main:20 010111010000101110111011' \
GOFMAHASH=01110111011 GOMAGIC=GOFMAHASH go run fma.go
Change-Id: Ifa22dd8f1c37c18fc8a4f7c396345a364bc367d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/394754
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Randomized feature enable/disable might be something we use to
help users debug any problems with changed loop variable capture,
and there's another CL that would like to use it to help in
locating places where "fused" multiply add instructions change
program behavior.
This CL:
- adds the ability to include an integer parameter (e.g. line number)
- replumbed the environment variable into a flag to simplify go build cache management
- but added an environment variable to allow flag setting through the environment
- which adds the possibility of switching on a different variable
(if there's one built-in for variable capture, it shouldn't be GOSSAHASH)
- cleaned up the checking code
- adds tests for all the intended behavior
- removes the case for GSHS_LOGFILE; TBD whether we'll need to put that back
or if there is another way.
Change-Id: I8503e1bb3dbc4a743aea696e04411ea7ab884787
Reviewed-on: https://go-review.googlesource.com/c/go/+/443063
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Change-Id: I4dad103d23121a21b04800ec157487fdf79f89a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/424398
Run-TryBot: hopehook <hopehook@qq.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
I've needed this more than once in the past, I hack it in,
then throw it away, seems sensible to make the change and
save it.
Fixes#53937.
Change-Id: I7fe886b1c93d73cbf553bed587f2c30f0f5d5a0b
Reviewed-on: https://go-review.googlesource.com/c/go/+/418015
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Than McIntosh
Cuong Manh Le
guoguangwu
Danil Timerbulatov
Cherry Mui
David Chase
Russ Cox
hopehook