Revert "cmd/compile: make OpAddr depend on VarDef in storeOrder"

This reverts commit 1a27f048.

Reason for revert: Broke the ssacheck and -N-l builders, and the -N-l fix looks like it will take some time and take a different route entirely.

Change-Id: Ie0ac5e86ab7d72a303dfbbc48dfdf1e092d4f61a
Reviewed-on: https://go-review.googlesource.com/121715Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/ssa/schedule.go

@@ -310,7 +310,6 @@ func storeOrder(values []*Value, sset *sparseSet, storeNumber []int32) []*Value
 	// A constant bound allows this to be stack-allocated. 64 is
 	// enough to cover almost every storeOrder call.
 	stores := make([]*Value, 0, 64)
-	var vardefs map[interface{}]*Value // OpAddr must depend on Vardef for Node
 	hasNilCheck := false
 	sset.clear() // sset is the set of stores that are used in other values
 	for _, v := range values {
@@ -324,12 +323,6 @@ func storeOrder(values []*Value, sset *sparseSet, storeNumber []int32) []*Value
 		if v.Op == OpNilCheck {
 			hasNilCheck = true
 		}
-		if v.Op == OpVarDef {
-			if vardefs == nil { // Lazy init, not all blocks have vardefs
-				vardefs = make(map[interface{}]*Value)
-			}
-			vardefs[v.Aux] = v
-		}
 	}
 	if len(stores) == 0 || !hasNilCheck && f.pass.name == "nilcheckelim" {
 		// there is no store, the order does not matter
@@ -393,20 +386,7 @@ func storeOrder(values []*Value, sset *sparseSet, storeNumber []int32) []*Value
 				stack = stack[:len(stack)-1]
 				continue
 			}
-			if w.Op == OpAddr {
-				// OpAddr depends only on relevant VarDef
-				vn := int32(0)
-				if vardefs != nil {
-					if a := vardefs[w.Aux]; a != nil { // if nil, it is in some other block, or global or arg
-						vn = storeNumber[a.ID]
-					}
-				}
-				vn += 2
-				storeNumber[w.ID] = vn
-				count[vn]++
-				stack = stack[:len(stack)-1]
-				continue
-			}
+
 			max := int32(0) // latest store dependency
 			argsdone := true
 			for _, a := range w.Args {

test/fixedbugs/issue26105.go

-// compile
-
-// Copyright 2018 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.
-
-// Triggers a bug in writebarrier, which inserts one
-// between (first block) OpAddr x and (second block) a VarDef x,
-// which are then in the wrong order and unable to be
-// properly scheduled.
-
-package q
-
-var S interface{}
-
-func F(n int) {
-	fun := func(x int) int {
-		S = 1
-		return n
-	}
-	i := fun(([]int{})[n])
-
-	var fc [2]chan int
-	S = (([1][2]chan int{fc})[i][i])
-}