Implement jump tables (#453)

* Add 'jump_table_entry' and 'indirect_jump' instructions.

* Update CodeSink to keep track of code size. Pretty up clif-util's disassembly output.

* Only disassemble the machine portion of output. Pretty print the read-only data after it.

* Update switch frontend code to use new br_table instruction w/ default.

cranelift/filetests/isa/x86/binary64.clif

@@ -1402,3 +1402,41 @@ ebb0:
 
     trap user0                                          ; bin: user0 0f 0b
 }
+
+; Tests for i64 jump table instructions.
+function %I64_JT(i64 [%rdi]) {
+    jt0 = jump_table ebb1, ebb2, ebb3
+
+ebb0(v0: i64 [%rdi]):
+    ; Note: The next two lines will need to change whenever instructions are
+    ;        added or removed from this test.
+    [-, %rax]           v1 = jump_table_base.i64 jt0    ; bin: 48 8d 05 00000039
+    [-, %r10]           v2 = jump_table_base.i64 jt0    ; bin: 4c 8d 15 00000032
+
+    [-, %rbx]           v10 = iconst.i64 1
+    [-, %r13]           v11 = iconst.i64 2
+
+    [-, %rax]           v20 = jump_table_entry.i64 v10, v1, 4, jt0      ; bin: 48 63 04 98
+    [-, %rax]           v21 = jump_table_entry.i64 v10, v2, 4, jt0      ; bin: 49 63 04 9a
+    [-, %rax]           v22 = jump_table_entry.i64 v11, v1, 4, jt0      ; bin: 4a 63 04 a8
+    [-, %rax]           v23 = jump_table_entry.i64 v11, v2, 4, jt0      ; bin: 4b 63 04 aa
+
+    [-, %r10]           v30 = jump_table_entry.i64 v10, v1, 4, jt0      ; bin: 4c 63 14 98
+    [-, %r10]           v31 = jump_table_entry.i64 v10, v2, 4, jt0      ; bin: 4d 63 14 9a
+    [-, %r10]           v32 = jump_table_entry.i64 v11, v1, 4, jt0      ; bin: 4e 63 14 a8
+    [-, %r10]           v33 = jump_table_entry.i64 v11, v2, 4, jt0      ; bin: 4f 63 14 aa
+
+    fallthrough ebb10
+
+ebb10:
+    indirect_jump_table_br v10, jt0             ; bin: ff e3
+ebb11:
+    indirect_jump_table_br v11, jt0             ; bin: 41 ff e5
+
+ebb1:
+    fallthrough ebb2
+ebb2:
+    fallthrough ebb3
+ebb3:
+    trap user0
+}

cranelift/filetests/isa/x86/legalize-br-table.clif

@@ -9,7 +9,9 @@ function u0:0(i64) system_v {
 ebb0(v0: i64):
     v1 = stack_addr.i64 ss0
     v2 = load.i8 v1
-    br_table v2, jt0
+    br_table v2, ebb2, jt0
+
+ebb2:
     jump ebb1
 
 ebb1:

cranelift/filetests/parser/branch.clif

@@ -85,21 +85,22 @@ function %jumptable(i32) {
     jt2 = jump_table 0, 0, ebb10, ebb40, ebb20, ebb30
 
 ebb10(v3: i32):
-    br_table v3, jt2
-    trap user1
+    br_table v3, ebb50, jt2
+
 ebb20:
     trap user2
 ebb30:
     trap user3
 ebb40:
     trap user4
+ebb50:
+    trap user1    
 }
 ; sameln: function %jumptable(i32) fast {
 ; check:      jt2 = jump_table 0, 0, ebb10, ebb40, ebb20, ebb30
 ; check:      jt200 = jump_table 0
 ; check:  ebb10(v3: i32):
-; nextln:     br_table v3, jt2
-; nextln:     trap user1
+; nextln:     br_table v3, ebb50, jt2
 ; nextln: 
 ; nextln: ebb20:
 ; nextln:     trap user2
@@ -109,4 +110,7 @@ ebb40:
 ; nextln: 
 ; nextln: ebb40:
 ; nextln:     trap user4
+; nextln: 
+; nextln: ebb50:
+; nextln:     trap user1
 ; nextln: }

cranelift/filetests/verifier/type_check.clif

@@ -71,10 +71,12 @@ function %jump_table_args() {
     jt1 = jump_table ebb1
     ebb0:
         v0 = iconst.i32 0
-        br_table v0, jt1 ; error: takes no arguments, but had target ebb1 with 1 arguments
-        return
+        br_table v0, ebb2, jt1 ; error: takes no arguments, but had target ebb1 with 1 arguments
+
     ebb1(v5: i32):
         return
+    ebb2:
+        return
 }
 
 function %jump_args() {

cranelift/filetests/wasm/control.clif

@@ -51,7 +51,9 @@ function %br_table(i32) {
 jt0 = jump_table ebb3, ebb1, 0, ebb2
 
 ebb0(v0: i32):
-    br_table v0, jt0
+    br_table v0, ebb4, jt0
+
+ebb4:
     trap oob
 
 ebb1: