Today, this interface conversion causes the struct literal
to be heap allocated:
var sink any
func example1() {
sink = S{1, 1}
}
For basic literals like integers that are directly used in
an interface conversion that would otherwise allocate, the compiler
is able to use read-only global storage (see #18704).
This CL extends that to struct and array literals as well by creating
read-only global storage that is able to represent for example S{1, 1},
and then using a pointer to that storage in the interface
when the interface conversion happens.
A more challenging example is:
func example2() {
v := S{1, 1}
sink = v
}
In this case, the struct literal is not directly part of the
interface conversion, but is instead assigned to a local variable.
To still avoid heap allocation in cases like this, in walk we
construct a cache that maps from expressions used in interface
conversions to earlier expressions that can be used to represent the
same value (via ir.ReassignOracle.StaticValue). This is somewhat
analogous to how we avoided heap allocation for basic literals in
CL 649077 earlier in our stack, though here we also need to do a
little more work to create the read-only global.
CL 649076 (also earlier in our stack) added most of the tests
along with debug diagnostics in convert.go to make it easier
to test this change.
See the writeup in #71359 for details.
Fixes#71359Fixes#71323
Updates #62653
Updates #53465
Updates #8618
Change-Id: I8924f0c69ff738ea33439bd6af7b4066af493b90
Reviewed-on: https://go-review.googlesource.com/c/go/+/649555
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Since CL 391014, cmd/compile now requires the -p flag to be set the
build system. This CL changes it to initialize LocalPkg.Path to the
provided path, rather than relying on writing out `"".` into object
files and expecting cmd/link to substitute them.
However, this actually involved a rather long tail of fixes. Many have
already been submitted, but a few notable ones that have to land
simultaneously with changing LocalPkg:
1. When compiling package runtime, there are really two "runtime"
packages: types.LocalPkg (the source package itself) and
ir.Pkgs.Runtime (the compiler's internal representation, for synthetic
references). Previously, these ended up creating separate link
symbols (`"".xxx` and `runtime.xxx`, respectively), but now they both
end up as `runtime.xxx`, which causes lsym collisions (notably
inittask and funcsyms).
2. test/codegen tests need to be updated to expect symbols to be named
`command-line-arguments.xxx` rather than `"".foo`.
3. The issue20014 test case is sensitive to the sort order of field
tracking symbols. In particular, the local package now sorts to its
natural place in the list, rather than to the front.
Thanks to David Chase for helping track down all of the fixes needed
for this CL.
Updates #51734.
Change-Id: Iba3041cf7ad967d18c6e17922fa06ba11798b565
Reviewed-on: https://go-review.googlesource.com/c/go/+/393715
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Some codegen tests were written with the assumption that
arguments and results are in memory, and with a specific stack
layout. With the register ABI, the assumption is no longer true.
Adjust the tests to work with both cases.
- For tests expecting in memory arguments/results, change to use
global variables or memory-assigned argument/results.
- Allow more registers. E.g. some tests expecting register names
contain only letters (e.g. AX), but it can also contain numbers
(e.g. R10).
- Some instruction selection changes when operate on register vs.
memory, e.g. ADDQ vs. LEAQ, MOVB vs. MOVL. Accept both.
TODO: mathbits.go and memops.go still need fix.
Change-Id: Ic5932b4b5dd3f5d30ed078d296476b641420c4c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/309335
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>
If someone takes a pointer to a zero-sized stack variable, it can
be incorrectly interpreted as a pointer to the next object in the
stack frame. To avoid this, add some padding after zero-sized variables.
We only need to pad if the next variable in memory (which is the
previous variable in the order in which we allocate variables to the
stack frame) has pointers. If the next variable has no pointers, it
won't hurt to have a pointer to it.
Because we allocate all pointer-containing variables before all
non-pointer-containing variables, we should only have to pad once per
frame.
Fixes#24993
Change-Id: Ife561cdfdf964fdbf69af03ae6ba97d004e6193c
Reviewed-on: https://go-review.googlesource.com/c/155698
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
