mirror of
https://github.com/golang/go
synced 2024-09-24 01:30:13 -06:00
daca06f2e3
1. In functions with heap-allocated result variables or with defer statements, the return sequence requires more than just a single RET instruction. There is an optimization that arranges for all returns to jump to a single copy of the return epilogue in this case. Unfortunately, that optimization is fundamentally incompatible with PC-based liveness information: it takes PCs at many different points in the function and makes them all land at one PC, making the combined liveness information at that target PC a mess. Disable this optimization, so that each return site gets its own copy of the 'call deferreturn' and the copying of result variables back from the heap. This removes quite a few spurious 'ambiguously live' variables. 2. Let orderexpr allocate temporaries that are passed by address to a function call and then die on return, so that we can arrange an appropriate VARKILL. 2a. Do this for ... slices. 2b. Do this for closure structs. 2c. Do this for runtime.concatstring, which is the implementation of large string additions. Change representation of OADDSTR to an explicit list in typecheck to avoid reconstructing list in both walk and order. 3. Let orderexpr allocate the temporary variable copies used for range loops, so that they can be killed when the loop is over. Similarly, let it allocate the temporary holding the map iterator. CL 81940043 reduced the number of ambiguously live temps in the godoc binary from 860 to 711. This CL reduces the number to 121. Still more to do, but another good checkpoint. Update #7345 LGTM=khr R=khr CC=golang-codereviews https://golang.org/cl/83090046
426 lines
11 KiB
Go
426 lines
11 KiB
Go
// errorcheck -0 -l -live
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// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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func f1() {
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var x *int
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print(&x) // ERROR "live at call to printpointer: x$"
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print(&x) // ERROR "live at call to printpointer: x$"
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}
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func f2(b bool) {
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if b {
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print(0) // nothing live here
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return
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}
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var x *int
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print(&x) // ERROR "live at call to printpointer: x$"
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print(&x) // ERROR "live at call to printpointer: x$"
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}
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func f3(b bool) {
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print(0)
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if b == false {
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print(0) // nothing live here
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return
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}
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if b {
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var x *int
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print(&x) // ERROR "live at call to printpointer: x$"
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print(&x) // ERROR "live at call to printpointer: x$"
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} else {
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var y *int
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print(&y) // ERROR "live at call to printpointer: y$"
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print(&y) // ERROR "live at call to printpointer: y$"
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}
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print(0) // ERROR "live at call to printint: x y$" "x \(type \*int\) is ambiguously live" "y \(type \*int\) is ambiguously live"
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}
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// The old algorithm treated x as live on all code that
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// could flow to a return statement, so it included the
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// function entry and code above the declaration of x
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// but would not include an indirect use of x in an infinite loop.
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// Check that these cases are handled correctly.
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func f4(b1, b2 bool) { // x not live here
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if b2 {
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print(0) // x not live here
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return
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}
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var z **int
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x := new(int)
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*x = 42
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z = &x
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print(**z) // ERROR "live at call to printint: x z$"
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if b2 {
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print(1) // ERROR "live at call to printint: x$"
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return
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}
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for {
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print(**z) // ERROR "live at call to printint: x z$"
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}
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}
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func f5(b1 bool) {
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var z **int
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if b1 {
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x := new(int)
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*x = 42
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z = &x
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} else {
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y := new(int)
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*y = 54
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z = &y
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}
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print(**z) // ERROR "live at call to printint: x y$" "x \(type \*int\) is ambiguously live" "y \(type \*int\) is ambiguously live"
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}
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// confusion about the _ result used to cause spurious "live at entry to f6: _".
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func f6() (_, y string) {
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y = "hello"
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return
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}
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// confusion about addressed results used to cause "live at entry to f7: x".
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func f7() (x string) {
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_ = &x
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x = "hello"
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return
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}
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// ignoring block returns used to cause "live at entry to f8: x, y".
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func f8() (x, y string) {
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return g8()
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}
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func g8() (string, string)
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// ignoring block assignments used to cause "live at entry to f9: x"
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// issue 7205
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var i9 interface{}
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func f9() bool {
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g8()
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x := i9
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return x != 99
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}
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// liveness formerly confused by UNDEF followed by RET,
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// leading to "live at entry to f10: ~r1" (unnamed result).
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func f10() string {
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panic(1)
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}
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// liveness formerly confused by select, thinking runtime.selectgo
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// can return to next instruction; it always jumps elsewhere.
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// note that you have to use at least two cases in the select
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// to get a true select; smaller selects compile to optimized helper functions.
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var c chan *int
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var b bool
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// this used to have a spurious "live at entry to f11a: ~r0"
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func f11a() *int {
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select { // ERROR "live at call to selectgo: autotmp"
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case <-c: // ERROR "live at call to selectrecv: autotmp"
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return nil
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case <-c: // ERROR "live at call to selectrecv: autotmp"
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return nil
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}
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}
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func f11b() *int {
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p := new(int)
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if b {
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// At this point p is dead: the code here cannot
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// get to the bottom of the function.
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// This used to have a spurious "live at call to printint: p".
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print(1) // nothing live here!
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select { // ERROR "live at call to selectgo: autotmp"
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case <-c: // ERROR "live at call to selectrecv: autotmp"
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return nil
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case <-c: // ERROR "live at call to selectrecv: autotmp"
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return nil
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}
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}
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println(*p)
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return nil
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}
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func f11c() *int {
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p := new(int)
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if b {
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// Unlike previous, the cases in this select fall through,
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// so we can get to the println, so p is not dead.
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print(1) // ERROR "live at call to printint: p"
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select { // ERROR "live at call to newselect: p" "live at call to selectgo: autotmp.* p"
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case <-c: // ERROR "live at call to selectrecv: autotmp.* p"
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case <-c: // ERROR "live at call to selectrecv: autotmp.* p"
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}
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}
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println(*p)
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return nil
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}
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// similarly, select{} does not fall through.
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// this used to have a spurious "live at entry to f12: ~r0".
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func f12() *int {
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if b {
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select{}
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} else {
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return nil
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}
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}
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// incorrectly placed VARDEF annotations can cause missing liveness annotations.
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// this used to be missing the fact that s is live during the call to g13 (because it is
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// needed for the call to h13).
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func f13() {
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s := "hello"
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s = h13(s, g13(s)) // ERROR "live at call to g13: s"
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}
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func g13(string) string
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func h13(string, string) string
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// more incorrectly placed VARDEF.
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func f14() {
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x := g14()
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print(&x) // ERROR "live at call to printpointer: x"
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}
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func g14() string
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func f15() {
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var x string
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_ = &x
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x = g15() // ERROR "live at call to g15: x"
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print(x) // ERROR "live at call to printstring: x"
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}
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func g15() string
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// Checking that various temporaries do not persist or cause
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// ambiguously live values that must be zeroed.
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// The exact temporary names are inconsequential but we are
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// trying to check that there is only one at any given site,
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// and also that none show up in "ambiguously live" messages.
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var m map[string]int
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func f16() {
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if b {
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delete(m, "hi") // ERROR "live at call to mapdelete: autotmp_[0-9]+$"
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}
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delete(m, "hi") // ERROR "live at call to mapdelete: autotmp_[0-9]+$"
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delete(m, "hi") // ERROR "live at call to mapdelete: autotmp_[0-9]+$"
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}
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var m2s map[string]*byte
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var m2 map[[2]string]*byte
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var x2 [2]string
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var bp *byte
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func f17a() {
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// value temporary only
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if b {
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m2[x2] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
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}
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m2[x2] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
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m2[x2] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
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}
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func f17b() {
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// key temporary only
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if b {
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m2s["x"] = bp // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
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}
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m2s["x"] = bp // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
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m2s["x"] = bp // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
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}
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func f17c() {
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// key and value temporaries
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if b {
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m2s["x"] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
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}
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m2s["x"] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
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m2s["x"] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
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}
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func g18() [2]string
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func f18() {
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// key temporary for mapaccess.
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// temporary introduced by orderexpr.
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var z *byte
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if b {
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z = m2[g18()] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
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}
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z = m2[g18()] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
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z = m2[g18()] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
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print(z)
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}
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var ch chan *byte
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func f19() {
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// dest temporary for channel receive.
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var z *byte
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if b {
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z = <-ch // ERROR "live at call to chanrecv1: autotmp_[0-9]+$"
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}
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z = <-ch // ERROR "live at call to chanrecv1: autotmp_[0-9]+$"
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z = <-ch // ERROR "live at call to chanrecv1: autotmp_[0-9]+$"
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print(z)
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}
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func f20() {
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// src temporary for channel send
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if b {
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ch <- nil // ERROR "live at call to chansend1: autotmp_[0-9]+$"
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}
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ch <- nil // ERROR "live at call to chansend1: autotmp_[0-9]+$"
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ch <- nil // ERROR "live at call to chansend1: autotmp_[0-9]+$"
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}
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func f21() {
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// key temporary for mapaccess using array literal key.
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var z *byte
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if b {
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z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
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}
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z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
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z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
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print(z)
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}
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func f23() {
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// key temporary for two-result map access using array literal key.
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var z *byte
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var ok bool
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if b {
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z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: autotmp_[0-9]+$"
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}
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z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: autotmp_[0-9]+$"
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z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: autotmp_[0-9]+$"
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print(z, ok)
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}
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func f24() {
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// key temporary for map access using array literal key.
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// value temporary too.
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if b {
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m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
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}
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m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
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m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
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}
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// defer should not cause spurious ambiguously live variables
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func f25(b bool) {
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defer g25()
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if b {
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return
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}
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var x string
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_ = &x
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x = g15() // ERROR "live at call to g15: x"
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print(x) // ERROR "live at call to printstring: x"
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} // ERROR "live at call to deferreturn: x"
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func g25()
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// non-escaping ... slices passed to function call should die on return,
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// so that the temporaries do not stack and do not cause ambiguously
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// live variables.
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func f26(b bool) {
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if b {
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print26(1,2,3) // ERROR "live at call to print26: autotmp_[0-9]+$"
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}
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print26(4,5,6) // ERROR "live at call to print26: autotmp_[0-9]+$"
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print26(7,8,9) // ERROR "live at call to print26: autotmp_[0-9]+$"
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println()
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}
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//go:noescape
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func print26(...interface{})
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// non-escaping closures passed to function call should die on return
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func f27(b bool) {
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x := 0
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if b {
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call27(func() {x++}) // ERROR "live at call to call27: autotmp_[0-9]+$"
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}
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call27(func() {x++}) // ERROR "live at call to call27: autotmp_[0-9]+$"
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call27(func() {x++}) // ERROR "live at call to call27: autotmp_[0-9]+$"
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}
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//go:noescape
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func call27(func())
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// concatstring slice should die on return
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var s1, s2, s3, s4, s5, s6, s7, s8, s9, s10 string
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func f28(b bool) {
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if b {
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print(s1+s2+s3+s4+s5+s6+s7+s8+s9+s10) // ERROR "live at call to concatstrings: autotmp_[0-9]+$" "live at call to printstring: autotmp_[0-9]+$"
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}
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print(s1+s2+s3+s4+s5+s6+s7+s8+s9+s10) // ERROR "live at call to concatstrings: autotmp_[0-9]+$" "live at call to printstring: autotmp_[0-9]+$"
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print(s1+s2+s3+s4+s5+s6+s7+s8+s9+s10) // ERROR "live at call to concatstrings: autotmp_[0-9]+$" "live at call to printstring: autotmp_[0-9]+$"
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}
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// map iterator should die on end of range loop
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func f29(b bool) {
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if b {
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for k := range m { // ERROR "live at call to mapiterinit: autotmp_[0-9]+$" "live at call to mapiternext: autotmp_[0-9]+$"
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print(k) // ERROR "live at call to printstring: autotmp_[0-9]+$"
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}
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}
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for k := range m { // ERROR "live at call to mapiterinit: autotmp_[0-9]+$" "live at call to mapiternext: autotmp_[0-9]+$"
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print(k) // ERROR "live at call to printstring: autotmp_[0-9]+$"
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}
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for k := range m { // ERROR "live at call to mapiterinit: autotmp_[0-9]+$" "live at call to mapiternext: autotmp_[0-9]+$"
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print(k) // ERROR "live at call to printstring: autotmp_[0-9]+$"
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}
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}
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// copy of array of pointers should die at end of range loop
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var ptrarr [10]*int
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func f30(b bool) {
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// two live temps during print(p):
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// the copy of ptrarr and the internal iterator pointer.
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if b {
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for _, p := range ptrarr {
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print(p) // ERROR "live at call to printpointer: autotmp_[0-9]+ autotmp_[0-9]+$"
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}
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}
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for _, p := range ptrarr {
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print(p) // ERROR "live at call to printpointer: autotmp_[0-9]+ autotmp_[0-9]+$"
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}
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for _, p := range ptrarr {
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print(p) // ERROR "live at call to printpointer: autotmp_[0-9]+ autotmp_[0-9]+$"
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}
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}
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