src/cmd/compile/internal/liveness/plive.go    |  6 +++---
 src/cmd/compile/internal/typebits/typebits.go | 15 ++++++++++++---
 test/fixedbugs/issue54991.go                  | 29 +++++++++++++++++++++++++++++

diff --git a/src/cmd/compile/internal/liveness/plive.go b/src/cmd/compile/internal/liveness/plive.go
index 93f49fad454cb0c8107c964a7f4823e3a80ddfff..4e5a52ee547607d2679f63cf3b62c5233630153f 100644
--- a/src/cmd/compile/internal/liveness/plive.go
+++ b/src/cmd/compile/internal/liveness/plive.go
@@ -434,7 +434,7 @@ 			if !node.IsOutputParamInRegisters() {
 				if node.FrameOffset() < 0 {
 					lv.f.Fatalf("Node %v has frameoffset %d\n", node.Sym().Name, node.FrameOffset())
 				}
-				typebits.Set(node.Type(), node.FrameOffset(), args)
+				typebits.SetNoCheck(node.Type(), node.FrameOffset(), args)
 				break
 			}
 			fallthrough // PPARAMOUT in registers acts memory-allocates like an AUTO
@@ -1507,7 +1507,7 @@ 	nptr := int(abiInfo.ArgWidth() / int64(types.PtrSize))
 	bv := bitvec.New(int32(nptr) * 2)
 
 	for _, p := range abiInfo.InParams() {
-		typebits.Set(p.Type, p.FrameOffset(abiInfo), bv)
+		typebits.SetNoCheck(p.Type, p.FrameOffset(abiInfo), bv)
 	}
 
 	nbitmap := 1
@@ -1522,7 +1522,7 @@
 	if fn.Type().NumResults() > 0 {
 		for _, p := range abiInfo.OutParams() {
 			if len(p.Registers) == 0 {
-				typebits.Set(p.Type, p.FrameOffset(abiInfo), bv)
+				typebits.SetNoCheck(p.Type, p.FrameOffset(abiInfo), bv)
 			}
 		}
 		off = objw.BitVec(lsym, off, bv)
diff --git a/src/cmd/compile/internal/typebits/typebits.go b/src/cmd/compile/internal/typebits/typebits.go
index fddad6e7e84b8176fd3d2865433d53d0b95236b2..cd52830a49d03d7a1dca562c4f4143c3062fe8fa 100644
--- a/src/cmd/compile/internal/typebits/typebits.go
+++ b/src/cmd/compile/internal/typebits/typebits.go
@@ -14,7 +14,16 @@ // NOTE: The bitmap for a specific type t could be cached in t after
 // the first run and then simply copied into bv at the correct offset
 // on future calls with the same type t.
 func Set(t *types.Type, off int64, bv bitvec.BitVec) {
-	if uint8(t.Alignment()) > 0 && off&int64(uint8(t.Alignment())-1) != 0 {
+	set(t, off, bv, false)
+}
+
+// SetNoCheck is like Set, but do not check for alignment.
+func SetNoCheck(t *types.Type, off int64, bv bitvec.BitVec) {
+	set(t, off, bv, true)
+}
+
+func set(t *types.Type, off int64, bv bitvec.BitVec, skip bool) {
+	if !skip && uint8(t.Alignment()) > 0 && off&int64(uint8(t.Alignment())-1) != 0 {
 		base.Fatalf("typebits.Set: invalid initial alignment: type %v has alignment %d, but offset is %v", t, uint8(t.Alignment()), off)
 	}
 	if !t.HasPointers() {
@@ -72,13 +81,13 @@ 			// Short-circuit for #20739.
 			break
 		}
 		for i := int64(0); i < t.NumElem(); i++ {
-			Set(elt, off, bv)
+			set(elt, off, bv, skip)
 			off += elt.Size()
 		}
 
 	case types.TSTRUCT:
 		for _, f := range t.Fields().Slice() {
-			Set(f.Type, off+f.Offset, bv)
+			set(f.Type, off+f.Offset, bv, skip)
 		}
 
 	default:
diff --git a/test/fixedbugs/issue54991.go b/test/fixedbugs/issue54991.go
new file mode 100644
index 0000000000000000000000000000000000000000..9ab0f5d06cf653408384592d29f5bf867d0dc043
--- /dev/null
+++ b/test/fixedbugs/issue54991.go
@@ -0,0 +1,29 @@
+// compile
+
+// Copyright 2022 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
+
+import (
+	"sync/atomic"
+)
+
+type I interface {
+	M()
+}
+
+type S struct{}
+
+func (*S) M() {}
+
+type T struct {
+	I
+	x atomic.Int64
+}
+
+func F() {
+	t := &T{I: &S{}}
+	t.M()
+}