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Josh Bleecher Snyder a3fc77aa7e cmd/compile: add ellipsis rule diagnostics to rulegen
These detect opportunities to convert a rule to use an ellipsis,
and provide better error messages when something goes wrong.

This change was used to generate all the preceding changes
converting rules to use ellipses. This change is at the end of those
changes rather than the beginning in order to avoid log spam during rule
generation (say during a git bisection).

The preceding changes collectively shrink the cmd/compile binary by ~2.2%.

Part of this detection is also warning when the presence of an
unmentioned aux or auxint could cause conversion to an ellipsis
rule to change the sematics of the rule.

For example:

(Div64 x y) -> (DIV x y)

looks like a promising rule for an ellipsis. However, Div64 has an auxint,
and (on most platforms) DIV does not. An ellipsis rule would keep the
auxint intact, rather than zeroing it, which can infere with CSE.
So this change flags this rule as doing implicit zeroing;
it should be replaced by

(Div64 [a] x y) -> (DIV x y)

which makes it clear that the auxint is being zeroed.

This detection is not foolproof, but it currently has no false positives.
If false positives arise in the future, we will need to gate the output.

Change-Id: Ie21f284579e5d6e75aa304d0deb024d41ede528b
Reviewed-on: https://go-review.googlesource.com/c/go/+/217014
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
2020-02-28 13:21:44 +00:00
.github .github: add link to questions in ISSUE_TEMPLATE 2020-01-06 17:05:31 +00:00
api sync: add new Map method LoadAndDelete 2020-02-25 14:31:55 +00:00
doc cmd/go/internal/{test,vet}: use a standard flag.FlagSet to parse flags 2020-02-25 20:54:34 +00:00
lib/time lib/time: update tz data to 2019c 2019-11-26 12:03:08 +00:00
misc misc/wasm: avoid implicit boolean to number conversion 2020-02-25 21:08:47 +00:00
src cmd/compile: add ellipsis rule diagnostics to rulegen 2020-02-28 13:21:44 +00:00
test test: re-enable open-coded defer test on riscv64 2020-02-26 16:54:17 +00:00
.gitattributes
.gitignore .gitignore: ignore src/cmd/dist/dist 2017-10-28 21:55:49 +00:00
AUTHORS A+C: change email address for Akhil Indurti 2019-09-09 15:30:38 +00:00
CONTRIBUTING.md all: restore changes from faulty merge/revert 2018-02-12 20:13:59 +00:00
CONTRIBUTORS CONTRIBUTORS: second round of updates for Go 1.14 2020-02-21 19:59:34 +00:00
LICENSE doc: revert copyright date to 2009 2016-06-01 22:40:04 +00:00
PATENTS
README.md README: linkify some paths 2018-06-06 18:07:01 +00:00
SECURITY.md SECURITY.md: update go versions 2019-09-26 15:34:57 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
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README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

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