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zdjones 2d41444ad0 cmd/compile: make prove learn index >= 0 from successful bounds checks
When branching at a bounds check for indexing or slicing ops, prove currently
only learns from the upper bound. On the positive branch, we currently learn
i < len(a) (or i <= len(a)) in both the signed and unsigned domains.

This CL makes prove also learn from the lower bound. Specifically, on the
positive branch from index or slicing ops, prove will now ALSO learn i >= 0 in
the signed domain (this fact is of no value in the unsigned domain).

The substantive change itself is only an additional call to addRestrictions,
though I've also inverted the nested switch statements around that call for the
sake of clarity.

This CL removes 92 bounds checks from std and cmd. It passes all tests and
shows no deltas on compilecmp.

Fixes #28885

Change-Id: I13eccc36e640eb599fa6dc5aa3be3c7d7abd2d9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/170121
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
2019-03-30 23:22:02 +00:00
.github .github: don't render author-facing text in ISSUE_TEMPLATE 2018-11-02 04:47:34 +00:00
api text/scanner: don't liberally consume (invalid) floats or underbars 2019-02-20 20:23:28 +00:00
doc cmd/compile: add sign-extension operators on wasm 2019-03-28 20:23:05 +00:00
lib/time time: read 64-bit data if available 2019-02-26 23:10:35 +00:00
misc cmd/link: permit duplicate weak symbols 2019-03-29 17:46:01 +00:00
src cmd/compile: make prove learn index >= 0 from successful bounds checks 2019-03-30 23:22:02 +00:00
test cmd/compile: make prove learn index >= 0 from successful bounds checks 2019-03-30 23:22:02 +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 Elias Naur 2019-01-23 15:05:26 +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 1.12 2019-01-30 18:01:19 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
LICENSE
PATENTS
README.md README: linkify some paths 2018-06-06 18:07:01 +00:00
robots.txt

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