but this time, correctly.
children of Returns can have For/Range loops in them,
and those must be visited.
Includes test to verify that the optimization occurs,
and also that the problematic case that broke the original
optimization is now correctly handled.
Change-Id: If5a94fd51c862d4bfb318fec78456b7b202f3fcd
Reviewed-on: https://go-review.googlesource.com/c/go/+/472355
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This modifies the loopvar change to be tied to the
package if it is specified that way, and preserves
the change across inlining.
Down the road, this will be triggered (and flow correctly)
if the changed semantics are tied to Go version specified
in go.mod (or rather, for the compiler, by the specified
version for compilation).
Includes tests.
Change-Id: If54e8b6dd23273b86be5ba47838c90d38af9bd1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/463595
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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>
