aarch64: Implement bmask/bextend in ISLE (#4358)

* aarch64: Implement `bmask`/`bextend` in ISLE

* cranelift: Remove vector versions of `bextend`

* aarch64: Cleanup `bmask`/`bextend` documentation

cranelift/filetests/filetests/isa/aarch64/bitops.clif

@@ -317,8 +317,8 @@ block0:
 }
 
 ; block0:
-;   movz x2, #255
-;   sxtb w0, w2
+;   movz x1, #255
+;   sxtb w0, w1
 ;   ret
 
 function %bextend_b1() -> b32 {
@@ -329,8 +329,8 @@ block0:
 }
 
 ; block0:
-;   movz x2, #1
-;   sbfx w0, w2, #0, #1
+;   movz x1, #1
+;   sbfx w0, w1, #0, #1
 ;   ret
 
 function %bnot_i32(i32) -> i32 {

cranelift/filetests/filetests/runtests/bmask.clif

@@ -1,4 +1,7 @@
 test interpret
+test run
+target aarch64
+target s390x
 
 function %bmask_b64_i64(b64) -> i64 {
 block0(v0: b64):

cranelift/filetests/filetests/runtests/i128-bextend.clif

@@ -1,4 +1,6 @@
 test interpret
+test run
+target aarch64
 
 function %bextend_b1_b128(b1) -> b128 {
 block0(v0: b1):

cranelift/filetests/filetests/runtests/i128-bmask.clif

@@ -1,4 +1,6 @@
 test interpret
+test run
+target aarch64
 
 function %bmask_b128_i128(b128) -> i128 {
 block0(v0: b128):