diff --git a/src/cmd/compile/internal/gc/alg.go b/src/cmd/compile/internal/gc/alg.go index e2e2374717e7db..2b63700569e453 100644 --- a/src/cmd/compile/internal/gc/alg.go +++ b/src/cmd/compile/internal/gc/alg.go @@ -646,17 +646,11 @@ func geneq(t *types.Type) *obj.LSym { // Build a list of conditions to satisfy. // The conditions are a list-of-lists. Conditions are reorderable // within each inner list. The outer lists must be evaluated in order. - // Even within each inner list, track their order so that we can preserve - // aspects of that order. (TODO: latter part needed?) - type nodeIdx struct { - n *Node - idx int - } - var conds [][]nodeIdx - conds = append(conds, []nodeIdx{}) + var conds [][]*Node + conds = append(conds, []*Node{}) and := func(n *Node) { i := len(conds) - 1 - conds[i] = append(conds[i], nodeIdx{n: n, idx: len(conds[i])}) + conds[i] = append(conds[i], n) } // Walk the struct using memequal for runs of AMEM @@ -674,7 +668,7 @@ func geneq(t *types.Type) *obj.LSym { if !IsRegularMemory(f.Type) { if EqCanPanic(f.Type) { // Enforce ordering by starting a new set of reorderable conditions. - conds = append(conds, []nodeIdx{}) + conds = append(conds, []*Node{}) } p := nodSym(OXDOT, np, f.Sym) q := nodSym(OXDOT, nq, f.Sym) @@ -688,7 +682,7 @@ func geneq(t *types.Type) *obj.LSym { } if EqCanPanic(f.Type) { // Also enforce ordering after something that can panic. - conds = append(conds, []nodeIdx{}) + conds = append(conds, []*Node{}) } i++ continue @@ -713,14 +707,13 @@ func geneq(t *types.Type) *obj.LSym { // Sort conditions to put runtime calls last. // Preserve the rest of the ordering. - var flatConds []nodeIdx + var flatConds []*Node for _, c := range conds { + isCall := func(n *Node) bool { + return n.Op == OCALL || n.Op == OCALLFUNC + } sort.SliceStable(c, func(i, j int) bool { - x, y := c[i], c[j] - if (x.n.Op != OCALL) == (y.n.Op != OCALL) { - return x.idx < y.idx - } - return x.n.Op != OCALL + return !isCall(c[i]) && isCall(c[j]) }) flatConds = append(flatConds, c...) } @@ -729,9 +722,9 @@ func geneq(t *types.Type) *obj.LSym { if len(flatConds) == 0 { cond = nodbool(true) } else { - cond = flatConds[0].n + cond = flatConds[0] for _, c := range flatConds[1:] { - cond = nod(OANDAND, cond, c.n) + cond = nod(OANDAND, cond, c) } } diff --git a/test/fixedbugs/issue8606b.go b/test/fixedbugs/issue8606b.go new file mode 100644 index 00000000000000..448ea566f0bea0 --- /dev/null +++ b/test/fixedbugs/issue8606b.go @@ -0,0 +1,63 @@ +// run + +// Copyright 2020 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. + +// This is an optimization check. We want to make sure that we compare +// string lengths, and other scalar fields, before checking string +// contents. There's no way to verify this in the language, and +// codegen tests in test/codegen can't really detect ordering +// optimizations like this. Instead, we generate invalid strings with +// bad backing store pointers but nonzero length, so we can check that +// the backing store never gets compared. +// +// We use two different bad strings so that pointer comparisons of +// backing store pointers fail. + +package main + +import ( + "fmt" + "reflect" + "unsafe" +) + +func bad1() string { + s := "foo" + (*reflect.StringHeader)(unsafe.Pointer(&s)).Data = 1 // write bad value to data ptr + return s +} +func bad2() string { + s := "foo" + (*reflect.StringHeader)(unsafe.Pointer(&s)).Data = 2 // write bad value to data ptr + return s +} + +type SI struct { + s string + i int +} + +type SS struct { + s string + t string +} + +func main() { + for _, test := range []struct { + a, b interface{} + }{ + {SI{s: bad1(), i: 1}, SI{s: bad2(), i: 2}}, + {SS{s: bad1(), t: "a"}, SS{s: bad2(), t: "aa"}}, + {SS{s: "a", t: bad1()}, SS{s: "b", t: bad2()}}, + // This one would panic because the length of both strings match, and we check + // the body of the bad strings before the body of the good strings. + //{SS{s: bad1(), t: "a"}, SS{s: bad2(), t: "b"}}, + } { + if test.a == test.b { + panic(fmt.Sprintf("values %#v and %#v should not be equal", test.a, test.b)) + } + } + +}