cmd/compile: always mark atColumn1 results as statements

In 31618, we end up comparing the is-stmt-ness of positions
to repurpose real instructions as inline marks. If the is-stmt-ness
doesn't match, we end up not being able to remove the inline mark.

Always use statement-full positions to do the matching, so we
always find a match if there is one.

Also always use positions that are statements for inline marks.

Fixes #31618

Change-Id: Idaf39bdb32fa45238d5cd52973cadf4504f947d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/173324
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/test/codegen/issue31618.go b/test/codegen/issue31618.go
new file mode 100644
index 0000000000..8effe2995b
--- /dev/null
+++ b/test/codegen/issue31618.go
@@ -0,0 +1,22 @@
+// asmcheck
+
+// Copyright 2019 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 codegen
+
+// Make sure we remove both inline marks in the following code.
+// Both +5 and +6 should map to real instructions, which can
+// be used as inline marks instead of explicit nops.
+func f(x int) int {
+	// amd64:-"XCHGL"
+	x = g(x) + 5
+	// amd64:-"XCHGL"
+	x = g(x) + 6
+	return x
+}
+
+func g(x int) int {
+	return x >> 3
+}