cmd/compile: fix register/offset calculation for trailing empty field case.

dr2chase · dr2chase · commit 45ca9ef5c123 · 2021-04-01T15:50:43.000Z
Includes test. Long term, need to make the offending code be more in terms of official types package offsets, instead of duplicating that logic. For golang#40724. Change-Id: Id33a153f10aed3289cc48d1f99a8e0f6ece9474d Reviewed-on: https://go-review.googlesource.com/c/go/+/306469 Trust: David Chase <drchase@google.com> Run-TryBot: David Chase <drchase@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Than McIntosh <thanm@google.com> Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/src/cmd/compile/internal/abi/abiutils.go b/src/cmd/compile/internal/abi/abiutils.go
@@ -211,8 +211,11 @@ func appendParamOffsets(offsets []int64, at int64, t *types.Type) ([]int64, int6
 				offsets, at = appendParamOffsets(offsets, at, t.Elem())
 			}
 		case types.TSTRUCT:
-			for _, f := range t.FieldSlice() {
+			for i, f := range t.FieldSlice() {
 				offsets, at = appendParamOffsets(offsets, at, f.Type)
+				if f.Type.Width == 0 && i == t.NumFields()-1 {
+					at++ // last field has zero width
+				}
 			}
 			at = align(at, t) // type size is rounded up to its alignment
 		case types.TSLICE:
diff --git a/test/abi/fuzz_trailing_zero_field.go b/test/abi/fuzz_trailing_zero_field.go
@@ -0,0 +1,39 @@
+// run
+
+// 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 main
+
+var p0exp = S1{
+	F1: complex(float64(2.3640607624715027), float64(-0.2717825524109192)),
+	F2: S2{F1: 9},
+	F3: 103050709,
+}
+
+type S1 struct {
+	F1 complex128
+	F2 S2
+	F3 uint64
+}
+
+type S2 struct {
+	F1 uint64
+	F2 empty
+}
+
+type empty struct {
+}
+
+//go:noinline
+//go:registerparams
+func callee(p0 S1) {
+	if p0 != p0exp {
+		panic("bad p0")
+	}
+}
+
+func main() {
+	callee(p0exp)
+}

Original file line number	Diff line number	Diff line change
`@@ -211,8 +211,11 @@ func appendParamOffsets(offsets []int64, at int64, t *types.Type) ([]int64, int6`
`211`	`211`	`offsets, at = appendParamOffsets(offsets, at, t.Elem())`
`212`	`212`	`}`
`213`	`213`	`case types.TSTRUCT:`
`214`		`- for _, f := range t.FieldSlice() {`
	`214`	`+ for i, f := range t.FieldSlice() {`
`215`	`215`	`offsets, at = appendParamOffsets(offsets, at, f.Type)`
	`216`	`+ if f.Type.Width == 0 && i == t.NumFields()-1 {`
	`217`	`+ at++ // last field has zero width`
	`218`	`+ }`
`216`	`219`	`}`
`217`	`220`	`at = align(at, t) // type size is rounded up to its alignment`
`218`	`221`	`case types.TSLICE:`