Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

cmd/compile: missing BCE case #41335

Open
choleraehyq opened this issue Sep 11, 2020 · 1 comment
Open

cmd/compile: missing BCE case #41335

choleraehyq opened this issue Sep 11, 2020 · 1 comment
Labels
compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Unplanned

Comments

@choleraehyq
Copy link
Contributor

What version of Go are you using (go version)?

$ go version
go version go1.15.2 darwin/amd64

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/cholerae/Library/Caches/go-build"
GOENV="/Users/cholerae/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/cholerae/Documents/gopath/pkg/mod"
GONOPROXY="code.byted.org,git.byted.org"
GONOSUMDB="code.byted.org,git.byted.org"
GOOS="darwin"
GOPATH="/Users/cholerae/Documents/gopath"
GOPRIVATE="code.byted.org,git.byted.org"
GOPROXY="https://goproxy.cn,direct"
GOROOT="/Users/cholerae/Documents/gopath/go"
GOSUMDB="sum.golang.google.cn"
GOTMPDIR=""
GOTOOLDIR="/Users/cholerae/Documents/gopath/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

https://godbolt.org/z/31M9no

package main

//go:noinline
func test(val uint, dst []byte) byte {
    if val+3 > val {
        _ = dst[val+3]
        dst[val] = 1
        dst[val+1] = 1
        dst[val+2] = 1
        dst[val+3] = 1
    }
    return 1
}

func main() {
    println(test(100, make([]byte, 10)))
}

Bound checks in function test after _ = dst[val+3] could be eliminated, but not.

What did you expect to see?

Only one bound check exists in function test.

What did you see instead?

There are three bound checks in function test.
@ALTree ALTree added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Sep 14, 2020
@ALTree ALTree added this to the Unplanned milestone Sep 14, 2020
@mdempsky
Copy link
Member

FYI, you can write that if body as:

t := dst[val : val+4]
t[0] = 1
t[1] = 1
t[2] = 1
t[3] = 1

and then there will be no bounds checks for the individual assignments.

@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Jul 13, 2022
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Projects
None yet
Milestone
Unplanned
Development

No branches or pull requests
4 participants
@mdempsky @ALTree @gopherbot @choleraehyq