Convert the CFG traversal tests to file tests.

Add a "cfg_postorder:" printout to the "test domtree" file tests and use
that to check the computed CFG post-order instead of doing it manually
with Rust code.

cranelift/filetests/cfg/loop.cton

@@ -3,7 +3,7 @@ test print-cfg
 test verifier
 
 function %nonsense(i32, i32) -> f32 {
-; check: digraph %nonsense {
+; check: digraph "%nonsense" {
 ; regex: I=\binst\d+\b
 ; check: label="{ebb0 | <$(BRZ=$I)>brz ebb2 | <$(JUMP=$I)>jump ebb1}"]
 

cranelift/filetests/cfg/traps_early.cton

@@ -4,7 +4,7 @@ test print-cfg
 test verifier
 
 function %nonsense(i32) {
-; check: digraph %nonsense {
+; check: digraph "%nonsense" {
 
 ebb0(v1: i32):
     trap user0      ; error: terminator instruction was encountered before the end

cranelift/filetests/cfg/unused_node.cton

@@ -2,7 +2,7 @@
 test print-cfg
 
 function %not_reached(i32) -> i32 {
-; check: digraph %not_reached {
+; check: digraph "%not_reached" {
 ; check:     ebb0 [shape=record, label="{ebb0 | <inst0>brnz ebb2}"]
 ; check:     ebb1 [shape=record, label="{ebb1 | <inst4>jump ebb0}"]
 ; check:     ebb2 [shape=record, label="{ebb2}"]

cranelift/filetests/domtree/basic.cton

@@ -11,3 +11,8 @@ function %test(i32) {
     ebb3:
         return
 }
+; check: cfg_postorder:
+; sameln: ebb2
+; sameln: ebb3
+; sameln: ebb1
+; sameln: ebb0

cranelift/filetests/domtree/loops.cton

@@ -18,3 +18,67 @@ function %test(i32) {
         brz v0, ebb4
         return
 }
+; Fall-through-first, prune-at-source DFT:
+;
+; ebb0 {
+;     ebb0:brz v0, ebb1 {
+;         ebb0:jump ebb2 {
+;             ebb2 {
+;                 ebb2:brz v2, ebb2 -
+;                 ebb2:brz v3, ebb1 -
+;                 ebb2:brz v4, ebb4 {
+;                     ebb2: jump ebb5 {
+;                         ebb5 {}
+;                     }
+;                     ebb4 {}
+;                 }
+;             } ebb2
+;         }
+;         ebb1 {
+;             ebb1:jump ebb3 {
+;                 ebb3 {}
+;             }
+;         } ebb1
+;     }
+; } ebb0
+;
+; check: cfg_postorder:
+; sameln: ebb5
+; sameln: ebb3
+; sameln: ebb4
+; sameln: ebb2
+; sameln: ebb1
+; sameln: ebb0
+
+function %loop2(i32) native {
+    ebb0(v0: i32):
+        brz v0, ebb1    ; dominates: ebb1 ebb3 ebb4 ebb5
+        jump ebb2       ; dominates: ebb2
+    ebb1:
+        jump ebb3
+    ebb2:
+        brz v0, ebb4
+        jump ebb5
+    ebb3:
+        jump ebb4
+    ebb4:
+        brz v0, ebb3
+        brnz v0, ebb5
+        jump ebb6       ; dominates: ebb6
+    ebb5:
+        brz v0, ebb4
+        trap user0
+    ebb6:
+        jump ebb7       ; dominates: ebb7
+    ebb7:
+        return
+}
+; check: cfg_postorder:
+; sameln: ebb5
+; sameln: ebb7
+; sameln: ebb6
+; sameln: ebb3
+; sameln: ebb4
+; sameln: ebb2
+; sameln: ebb1
+; sameln: ebb0

cranelift/filetests/domtree/loops2.cton

@@ -29,3 +29,29 @@ function %test(i32) {
     ebb9:
         return
 }
+
+function %test(i32) native {
+    ebb0(v0: i32):
+        brz v0, ebb1    ; dominates: ebb1 ebb3 ebb4 ebb5
+        jump ebb2       ; dominates: ebb2
+    ebb1:
+        jump ebb3
+    ebb2:
+        brz v0, ebb4
+        jump ebb5
+    ebb3:
+        jump ebb4
+    ebb4:
+        brz v0, ebb3
+        jump ebb5
+    ebb5:
+        brz v0, ebb4
+        return
+}
+; check: cfg_postorder:
+; sameln: ebb5
+; sameln: ebb3
+; sameln: ebb4
+; sameln: ebb2
+; sameln: ebb1
+; sameln: ebb0