go/compile: corrupted function return value #23812
Description
What version of Go are you using (go version)?
go version go1.9.4 linux/amd64
Does this issue reproduce with the latest release?
Yes (go version devel +2010189407 Tue Feb 13 16:34:46 2018 +0000 linux/amd64)
What operating system and processor architecture are you using (go env)?
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/jnml"
GORACE=""
GOROOT="/home/jnml/go"
GOTOOLDIR="/home/jnml/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build334481324=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
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?
// Minimized reproducer for the (incorrect) translation of github.com/gcc-mirror/gcc/gcc/testsuite/gcc.c-torture/execute/pr70429.c
package main
func main() {
if foo(1) != int32(0x3edae8) {
panic(42)
}
}
func foo(_a int32) (r int32) {
//defer func() { println("r ", r) }() // <- Uncommenting this defer statement makes the panic go away.
return shr1(int32(shr2(int64(0x14ff6e2207db5d1f), int(_a))), 4)
}
func shr1(n int32, m int) int32 { return n >> uint(m) }
func shr2(n int64, m int) int64 {
if m < 0 { // <- Commenting out this if statement makes the panic go away.
m = -m
}
if m >= 64 { // <- Commenting out this if statement makes the panic go away.
return n
}
return n >> uint(m)
}What did you expect to see?
No panic.
What did you see instead?
Panic.