tests/fixedbugs: regression test for issue 100 (#129)

Adds a regression test based on klauspost/compress#186. This necessitated some related changes:

* Mark "RET" as a terminal instruction
* printer refactor to maintain compatibility with asmfmt
* Tweaks to other regression tests to ensure they are run correctly in CI

Updates #100 #65 #8

tests/fixedbugs/issue65/asm.go

@@ -1,11 +1,4 @@
-// +build generate
-
-//go:generate go run $GOFILE
-
-// Regression test for a bug where casting a physical register would give the
-// error "non physical register found".
-//
-// See: https://github.com/mmcloughlin/avo/issues/65#issuecomment-576850145
+// +build ignore
 
 package main
 

tests/fixedbugs/issue65/doc.go

@@ -0,0 +1,9 @@
+// Package issue65 is a regression test for a bug involving casting physical registers.
+//
+// Regression test for a bug where casting a physical register would give the
+// error "non physical register found".
+//
+// See: https://github.com/mmcloughlin/avo/issues/65#issuecomment-576850145
+package issue65
+
+//go:generate go run asm.go -out issue65.s -stubs stub.go

tests/fixedbugs/issue65/issue65.s

@@ -0,0 +1,9 @@
+// Code generated by command: go run asm.go -out issue65.s -stubs stub.go. DO NOT EDIT.
+
+#include "textflag.h"
+
+// func Issue65()
+// Requires: AVX2
+TEXT ·Issue65(SB), NOSPLIT, $0
+	VINSERTI128 $0x01, X0, Y1, Y2
+	RET

tests/fixedbugs/issue65/stub.go

@@ -0,0 +1,5 @@
+// Code generated by command: go run asm.go -out issue65.s -stubs stub.go. DO NOT EDIT.
+
+package issue65
+
+func Issue65()