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author | khr@golang.org <khr@golang.org> | 2024-05-03 12:55:34 -0700 |
---|---|---|
committer | Keith Randall <khr@google.com> | 2024-05-06 18:10:50 +0000 |
commit | 58e77ad9b9e2b3323c1d8c1cb5e701412e206368 (patch) | |
tree | 898fa319130e28bcd136f9f2dcdd28c25e1a9800 | |
parent | 891ac91e5c395087bfa28ba5194e1ab95ee732ba (diff) | |
download | go-58e77ad9b9e2b3323c1d8c1cb5e701412e206368.tar.gz go-58e77ad9b9e2b3323c1d8c1cb5e701412e206368.zip |
[release-branch.go1.21] cmd/compile: don't combine loads in generated equality functions
... if the architecture can't do unaligned loads.
We already handle this in a few places, but this particular place
was added in CL 399542 and missed this additional restriction.
Fixes #67164
Change-Id: I45988f11ff3ed45df1c4da3f0931ab1fdb22dbfe
Reviewed-on: https://go-review.googlesource.com/c/go/+/583175
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Auto-Submit: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Derek Parker <parkerderek86@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
(cherry picked from commit 3c72dd513c30df60c0624360e98a77c4ae7ca7c8)
Reviewed-on: https://go-review.googlesource.com/c/go/+/583303
-rw-r--r-- | src/cmd/compile/internal/compare/compare.go | 7 | ||||
-rw-r--r-- | test/fixedbugs/issue67160.go | 32 |
2 files changed, 38 insertions, 1 deletions
diff --git a/src/cmd/compile/internal/compare/compare.go b/src/cmd/compile/internal/compare/compare.go index 1674065556..e848e1c858 100644 --- a/src/cmd/compile/internal/compare/compare.go +++ b/src/cmd/compile/internal/compare/compare.go @@ -148,7 +148,7 @@ func calculateCostForType(t *types.Type) int64 { return EqStructCost(t) case types.TSLICE: // Slices are not comparable. - base.Fatalf("eqStructFieldCost: unexpected slice type") + base.Fatalf("calculateCostForType: unexpected slice type") case types.TARRAY: elemCost := calculateCostForType(t.Elem()) cost = t.NumElem() * elemCost @@ -374,6 +374,11 @@ func eqmem(p ir.Node, q ir.Node, field *types.Sym, size int64) ir.Node { } func eqmemfunc(size int64, t *types.Type) (fn *ir.Name, needsize bool) { + if !base.Ctxt.Arch.CanMergeLoads && t.Alignment() < int64(base.Ctxt.Arch.Alignment) && t.Alignment() < t.Size() { + // We can't use larger comparisons if the value might not be aligned + // enough for the larger comparison. See issues 46283 and 67160. + size = 0 + } switch size { default: fn = typecheck.LookupRuntime("memequal") diff --git a/test/fixedbugs/issue67160.go b/test/fixedbugs/issue67160.go new file mode 100644 index 0000000000..be45a61420 --- /dev/null +++ b/test/fixedbugs/issue67160.go @@ -0,0 +1,32 @@ +// run + +// Copyright 2024 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. + +// Test to make sure that we don't try using larger loads for +// generated equality functions on architectures that can't do +// unaligned loads. + +package main + +// T has a big field that wants to be compared with larger loads/stores. +// T is "special" because of the unnamed field, so it needs a generated equality function. +// T is an odd number of bytes in size and has alignment 1. +type T struct { + src [8]byte + _ byte +} + +// U contains 8 copies of T, each at a different %8 alignment. +type U [8]T + +//go:noinline +func f(x, y *U) bool { + return *x == *y +} + +func main() { + var a U + _ = f(&a, &a) +} |