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![Matthew Dempsky](/assets/img/avatar_default.png)
Currently, during walk we rewrite PAUTOHEAP uses into derefs of their corresponding Heapaddr, but we can easily do this instead during SSA construction. This does involve updating two test cases: * nilptr3.go This file had a test that we emit a "removed nil check" diagnostic for the implicit dereference from accessing a PAUTOHEAP variable. This CL removes this diagnostic, since it's not really useful to end users: from the user's point of view, there's no pointer anyway, so they needn't care about whether we check for nil or not. That's a purely internal detail. And with the PAUTOHEAP dereference handled during SSA construction, we can more robustly ensure this happens, rather than relying on setting a flag in walk and hoping that SSA sees it. * issue20780.go Previously, when PAUTOHEAPs were dereferenced during walk, it had a consequence that when they're passed as a function call argument, they would first get copied to the stack before being copied to their actual destination. Moving the dereferencing to SSA had a side-effect of eliminating this unnecessary temporary, and copying directly to the destination parameter. The test is updated to instead call "g(h(), h())" where h() returns a large value, as the first result will always need to be spilled somewhere will calling the second function. Maybe eventually we're smart enough to realize it can be spilled to the heap, but we don't do that today. Because I'm concerned that the direct copy-to-parameter optimization could interfere with race-detector instrumentation (e.g., maybe the copies were previously necessary to ensure they're not clobbered by inserted raceread calls?), I've also added issue20780b.go to exercise this in a few different ways. Change-Id: I720598cb32b17518bc10a03e555620c0f25fd28d Reviewed-on: https://go-review.googlesource.com/c/go/+/281293 Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Go Bot <gobot@golang.org> Trust: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
244 lines
5.4 KiB
Go
244 lines
5.4 KiB
Go
// errorcheck -0 -d=nil
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// +build !wasm
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// +build !aix
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// Copyright 2013 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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// Test that nil checks are removed.
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// Optimization is enabled.
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package p
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type Struct struct {
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X int
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Y float64
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}
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type BigStruct struct {
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X int
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Y float64
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A [1 << 20]int
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Z string
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}
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type Empty struct {
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}
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type Empty1 struct {
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Empty
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}
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var (
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intp *int
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arrayp *[10]int
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array0p *[0]int
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bigarrayp *[1 << 26]int
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structp *Struct
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bigstructp *BigStruct
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emptyp *Empty
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empty1p *Empty1
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)
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func f1() {
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_ = *intp // ERROR "generated nil check"
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// This one should be removed but the block copy needs
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// to be turned into its own pseudo-op in order to see
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// the indirect.
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_ = *arrayp // ERROR "generated nil check"
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// 0-byte indirect doesn't suffice.
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// we don't registerize globals, so there are no removed.* nil checks.
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_ = *array0p // ERROR "generated nil check"
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_ = *array0p // ERROR "removed nil check"
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_ = *intp // ERROR "removed nil check"
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_ = *arrayp // ERROR "removed nil check"
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_ = *structp // ERROR "generated nil check"
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_ = *emptyp // ERROR "generated nil check"
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_ = *arrayp // ERROR "removed nil check"
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}
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func f2() {
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var (
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intp *int
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arrayp *[10]int
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array0p *[0]int
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bigarrayp *[1 << 20]int
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structp *Struct
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bigstructp *BigStruct
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emptyp *Empty
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empty1p *Empty1
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)
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_ = *intp // ERROR "generated nil check"
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_ = *arrayp // ERROR "generated nil check"
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_ = *array0p // ERROR "generated nil check"
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_ = *array0p // ERROR "removed.* nil check"
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_ = *intp // ERROR "removed.* nil check"
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_ = *arrayp // ERROR "removed.* nil check"
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_ = *structp // ERROR "generated nil check"
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_ = *emptyp // ERROR "generated nil check"
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_ = *arrayp // ERROR "removed.* nil check"
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_ = *bigarrayp // ERROR "generated nil check" ARM removed nil check before indirect!!
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_ = *bigstructp // ERROR "generated nil check"
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_ = *empty1p // ERROR "generated nil check"
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}
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func fx10k() *[10000]int
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var b bool
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func f3(x *[10000]int) {
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// Using a huge type and huge offsets so the compiler
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// does not expect the memory hardware to fault.
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_ = x[9999] // ERROR "generated nil check"
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for {
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if x[9999] != 0 { // ERROR "removed nil check"
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break
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}
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}
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x = fx10k()
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_ = x[9999] // ERROR "generated nil check"
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if b {
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_ = x[9999] // ERROR "removed.* nil check"
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} else {
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_ = x[9999] // ERROR "removed.* nil check"
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}
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_ = x[9999] // ERROR "removed nil check"
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x = fx10k()
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if b {
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_ = x[9999] // ERROR "generated nil check"
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} else {
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_ = x[9999] // ERROR "generated nil check"
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}
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_ = x[9999] // ERROR "generated nil check"
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fx10k()
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// This one is a bit redundant, if we figured out that
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// x wasn't going to change across the function call.
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// But it's a little complex to do and in practice doesn't
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// matter enough.
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_ = x[9999] // ERROR "removed nil check"
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}
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func f3a() {
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x := fx10k()
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y := fx10k()
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z := fx10k()
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_ = &x[9] // ERROR "generated nil check"
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y = z
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_ = &x[9] // ERROR "removed.* nil check"
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x = y
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_ = &x[9] // ERROR "generated nil check"
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}
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func f3b() {
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x := fx10k()
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y := fx10k()
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_ = &x[9] // ERROR "generated nil check"
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y = x
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_ = &x[9] // ERROR "removed.* nil check"
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x = y
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_ = &x[9] // ERROR "removed.* nil check"
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}
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func fx10() *[10]int
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func f4(x *[10]int) {
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// Most of these have no checks because a real memory reference follows,
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// and the offset is small enough that if x is nil, the address will still be
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// in the first unmapped page of memory.
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_ = x[9] // ERROR "generated nil check" // bug: would like to remove this check (but nilcheck and load are in different blocks)
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for {
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if x[9] != 0 { // ERROR "removed nil check"
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break
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}
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}
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x = fx10()
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_ = x[9] // ERROR "generated nil check" // bug would like to remove before indirect
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if b {
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_ = x[9] // ERROR "removed nil check"
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} else {
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_ = x[9] // ERROR "removed nil check"
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}
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_ = x[9] // ERROR "removed nil check"
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x = fx10()
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if b {
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_ = x[9] // ERROR "generated nil check" // bug would like to remove before indirect
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} else {
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_ = &x[9] // ERROR "generated nil check"
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}
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_ = x[9] // ERROR "generated nil check" // bug would like to remove before indirect
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fx10()
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_ = x[9] // ERROR "removed nil check"
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x = fx10()
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y := fx10()
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_ = &x[9] // ERROR "generated nil check"
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y = x
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_ = &x[9] // ERROR "removed[a-z ]* nil check"
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x = y
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_ = &x[9] // ERROR "removed[a-z ]* nil check"
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}
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func m1(m map[int][80]byte) byte {
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v := m[3] // ERROR "removed nil check"
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return v[5]
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}
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func m2(m map[int][800]byte) byte {
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v := m[3] // ERROR "removed nil check"
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return v[5]
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}
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func m3(m map[int][80]byte) (byte, bool) {
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v, ok := m[3] // ERROR "removed nil check"
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return v[5], ok
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}
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func m4(m map[int][800]byte) (byte, bool) {
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v, ok := m[3] // ERROR "removed nil check"
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return v[5], ok
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}
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func p1() byte {
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p := new([100]byte)
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return p[5] // ERROR "removed nil check"
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}
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type SS struct {
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x byte
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}
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type TT struct {
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SS
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}
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func f(t *TT) *byte {
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// See issue 17242.
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s := &t.SS // ERROR "generated nil check"
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return &s.x // ERROR "removed nil check"
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}
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// make sure not to do nil check for newobject
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func f7() (*Struct, float64) {
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t := new(Struct)
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p := &t.Y // ERROR "removed nil check"
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return t, *p // ERROR "removed nil check"
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}
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func f9() []int {
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x := new([1]int)
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x[0] = 1 // ERROR "removed nil check"
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y := x[:] // ERROR "removed nil check"
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return y
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}
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