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cmd/compile: regression in commit c6bf9a8109 #27829

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rski opened this issue Sep 24, 2018 · 2 comments
Closed

cmd/compile: regression in commit c6bf9a8109 #27829

rski opened this issue Sep 24, 2018 · 2 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Go1.12

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@rski
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rski commented Sep 24, 2018 •
edited

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

$ ../bin/go version
go version devel +ce536837d8 Sun Sep 23 19:59:57 2018 +0000 linux/amd64

Does this issue reproduce with the latest release?

No, only present in master

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

$  ../bin/go env    
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/rski/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/rski/go"
GOPROXY=""
GORACE=""
GOROOT="/home/rski/Code/go"
GOTMPDIR=""
GOTOOLDIR="/home/rski/Code/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
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"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build909293570=/tmp/go-build -gno-record-gcc-switches"

const mask = 0x4000

func TestGoRegression(t *testing.T) {
	value := uint64(100000000000000000)
	fmt.Println((value >> 48) & (^uint64(mask)))
	foo(value)
}

func foo(value uint64) {
	fmt.Println((value >> 48) & (^uint64(mask)))
}

 /home/rski/Code/go/bin/go test -run "TestGoRegression" ./... -v -count=1
=== RUN   TestGoRegression
355
0

However, this does the right thing:

const mask = 0x4000

func TestGoRegression(t *testing.T) {
	value := uint64(100000000000000000)
	fmt.Println((value >> 48) & (^uint64(mask)))
	fmt.Println(foo(value))
}

func foo(value uint64) uint64 {
	return ((value >> 48) & (^uint64(mask)))
}

 /home/rski/Code/go/bin/go test -run "TestGoRegression" ./... -v -count=1
=== RUN   TestGoRegression
355
355
@mvdan
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mvdan commented Sep 24, 2018

Assigning to @benshi001, the commit author.

@mvdan mvdan added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Sep 24, 2018
@mvdan mvdan added this to the Go1.12 milestone Sep 24, 2018
@gopherbot
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Change https://golang.org/cl/136899 mentions this issue: cmd/compile: &^ and << have equal precedence

@golang golang locked and limited conversation to collaborators Sep 24, 2019
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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Milestone
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@rski @mvdan @gopherbot @benshi001