[release-branch.go1.16] cmd/compile: avoid adding LECall to the entry block when...

The openDeferRecord always insert vardef/varlive pairs into the entry block, it may destroy the mem chain when LECall's args are writing into the same block. So create a new block before that happens.

Fixes #49412

Change-Id: Ibda6c4a45d960dd412a641f5e02276f663c80785
Reviewed-on: https://go-review.googlesource.com/c/go/+/361410
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Alberto Donizetti <alb.donizetti@gmail.com>
Trust: Than McIntosh <thanm@google.com>
Reviewed-by: David Chase <drchase@google.com>
(cherry picked from commit 4f083c7dcf6ace3e837b337e10cf2f4e3160677e)
Reviewed-on: https://go-review.googlesource.com/c/go/+/362055
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 5b74754b53291211f486cca9d28017ed1ce60f23..8975ad355919695d79a0b3e2127351e0c977b3d2 100644 (file)
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -4709,6 +4709,17 @@ func (s *state) call(n *Node, k callKind, returnResultAddr bool) *ssa.Value {
                        }
                }
 
+               // Split the entry block if there are open defers, because later calls to
+               // openDeferSave may cause a mismatch between the mem for an OpDereference
+               // and the call site which uses it. See #49282.
+               if s.curBlock.ID == s.f.Entry.ID && s.hasOpenDefers {
+                       b := s.endBlock()
+                       b.Kind = ssa.BlockPlain
+                       curb := s.f.NewBlock(ssa.BlockPlain)
+                       b.AddEdgeTo(curb)
+                       s.startBlock(curb)
+               }
+
                // Write args.
                t := n.Left.Type
                args := n.Rlist.Slice()

diff --git a/test/fixedbugs/issue49282.go b/test/fixedbugs/issue49282.go
new file mode 100644 (file)
index 0000000..7543075
--- /dev/null
+++ b/test/fixedbugs/issue49282.go
@@ -0,0 +1,44 @@
+// compile
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+//go:noinline
+func g(d uintptr, a, m []int, s struct {
+       a, b, c, d, e int
+}, u uint) {
+       _ = a
+       _ = m
+       _ = s
+       func() {
+               for i := 0; i < 5; i++ {
+                       _ = a
+                       _ = m
+                       _, _ = s, s
+               }
+       }()
+}
+
+var One float64 = 1.0
+
+func f(d uintptr) {
+       var a, m []int
+       var s struct {
+               a, b, c, d, e int
+       }
+
+       g(d, a, m, s, uint(One)) // Uint of not-a-constant inserts a conditional, necessary to bug
+
+       defer func() uint {
+               return 0
+       }()
+}
+
+var d uintptr
+
+func h() {
+       f(d)
+}