Return to more structured type rules for block and if (#1148)

* if a block has a concrete final element (or a break with a value), then even if it has an unreachable child, keep it with that concrete type. this means we no longe allow the silly case of a block with an unreachable in the middle and a concrete as the final element while the block is unreachable - after this change, the block would have the type of the final element

* if an if has a concrete element in one arm, make it have that type as a result, even if the if condition is unreachable, to parallel block

* make type rules for brs and switches simpler, ignore whether they are reachable or not. whether they are dead code should not affect how they influence other types in our IR.

18 files changed, 267 insertions, 92 deletions

diff --git a/test/passes/flatten-control-flow.txt b/test/passes/flatten-control-flow.txt
index d94536712..65e7196fb 100644
--- a/test/passes/flatten-control-flow.txt
+++ b/test/passes/flatten-control-flow.txt
@@ -1174,4 +1174,11 @@
    (get_local $2)
   )
  )
+ (func $switch-unreachable (type $1)
+  (block $label$3
+   (block
+    (unreachable)
+   )
+  )
+ )
 )
diff --git a/test/passes/flatten-control-flow.wast b/test/passes/flatten-control-flow.wast
index 69f3146c0..97ecf74c7 100644
--- a/test/passes/flatten-control-flow.wast
+++ b/test/passes/flatten-control-flow.wast
@@ -773,4 +773,11 @@
     (i32.const 1)
    )
   )
+  (func $switch-unreachable
+   (block $label$3
+    (br_table $label$3
+     (unreachable)
+    )
+   )
+  )
 )
diff --git a/test/passes/merge-blocks.txt b/test/passes/merge-blocks.txt
index f9ca7c3c1..be6906f0a 100644
--- a/test/passes/merge-blocks.txt
+++ b/test/passes/merge-blocks.txt
@@ -77,16 +77,12 @@
  )
  (func $drop-unreachable-br_if (type $2) (result i32)
   (block $label$0 (result i32)
-   (drop
-    (block $label$2
-     (drop
-      (br_if $label$2
-       (br $label$0
-        (i32.const 538976371)
-       )
-       (i32.const 1918987552)
-      )
+   (block $label$2 (result i32)
+    (br_if $label$2
+     (br $label$0
+      (i32.const 538976371)
      )
+     (i32.const 1918987552)
     )
    )
   )
diff --git a/test/passes/merge-blocks.wast b/test/passes/merge-blocks.wast
index d73612735..7cba9bf90 100644
--- a/test/passes/merge-blocks.wast
+++ b/test/passes/merge-blocks.wast
@@ -55,16 +55,12 @@
   )
   (func $drop-unreachable-br_if (result i32)
     (block $label$0 (result i32)
-     (drop
-      (block $label$2
-       (drop
-        (br_if $label$2
-         (br $label$0
-          (i32.const 538976371)
-         )
-         (i32.const 1918987552)
-        )
+     (block $label$2 (result i32)
+      (br_if $label$2
+       (br $label$0
+        (i32.const 538976371)
        )
+       (i32.const 1918987552)
       )
      )
     )
diff --git a/test/passes/optimize-instructions.txt b/test/passes/optimize-instructions.txt
index 55501dfb8..6a99ee106 100644
--- a/test/passes/optimize-instructions.txt
+++ b/test/passes/optimize-instructions.txt
@@ -355,8 +355,8 @@
   )
   (drop
    (i32.and
-    (unreachable)
     (i32.const 1)
+    (unreachable)
    )
   )
   (drop
@@ -2064,8 +2064,11 @@
  )
  (func $shifts-square-unreachable (type $3) (param $x i32) (result i32)
   (i32.shr_u
-   (unreachable)
-   (i32.const 9)
+   (i32.shr_u
+    (unreachable)
+    (i32.const 1031)
+   )
+   (i32.const 4098)
   )
  )
  (func $mix-shifts (type $2) (result i32)
diff --git a/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.txt b/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.txt
index 922f64008..85e0dd6d8 100644
--- a/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.txt
+++ b/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.txt
@@ -1,5 +1,6 @@
 (module
  (type $0 (func (param i32 i32) (result i32)))
+ (type $1 (func (result f64)))
  (memory $0 0)
  (func $conditionals (type $0) (param $0 i32) (param $1 i32) (result i32)
   (local $2 i32)
@@ -321,4 +322,41 @@
    (get_local $1)
   )
  )
+ (func $conditionalize-if-type-change (type $1) (result f64)
+  (local $0 i32)
+  (drop
+   (loop $label$1 (result f32)
+    (block $label$2 (result f32)
+     (drop
+      (block $label$3 (result f32)
+       (br_if $label$1
+        (i32.or
+         (f32.gt
+          (br_if $label$3
+           (f32.const 1)
+           (get_local $0)
+          )
+          (br $label$2
+           (f32.const 71)
+          )
+         )
+         (i64.eqz
+          (select
+           (i64.const 58)
+           (i64.const -982757)
+           (i64.eqz
+            (i64.const 0)
+           )
+          )
+         )
+        )
+       )
+      )
+     )
+     (f32.const 1)
+    )
+   )
+  )
+  (f64.const -nan:0xfffffffffffff)
+ )
 )
diff --git a/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.wast b/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.wast
index 7e8365812..6e19255ed 100644
--- a/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.wast
+++ b/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.wast
@@ -323,5 +323,43 @@
    )
    (return (get_local $1))
   )
+
+ (func $conditionalize-if-type-change (result f64)
+  (local $0 i32)
+  (drop
+   (loop $label$1 (result f32)
+    (block $label$2 (result f32)
+     (drop
+      (block $label$3 (result f32)
+       (br_if $label$1
+        (i32.or ;; this turns into an if, but then the if might not be unreachable
+         (f32.gt
+          (br_if $label$3
+           (f32.const 1)
+           (get_local $0)
+          )
+          (br $label$2
+           (f32.const 71)
+          )
+         )
+         (i64.eqz
+          (select
+           (i64.const 58)
+           (i64.const -982757)
+           (i64.eqz
+            (i64.const 0)
+           )
+          )
+         )
+        )
+       )
+      )
+     )
+     (f32.const 1)
+    )
+   )
+  )
+  (f64.const -nan:0xfffffffffffff)
+ )
 )
 
diff --git a/test/passes/precompute.txt b/test/passes/precompute.txt
index 74e4989dc..ad5b74e83 100644
--- a/test/passes/precompute.txt
+++ b/test/passes/precompute.txt
@@ -117,7 +117,7 @@
  )
  (func $br_if-condition-is-block-i32-but-unreachable-so-refinalize-tricky (type $2)
   (drop
-   (block $label$1
+   (block $label$1 (result i32)
     (drop
      (br_if $label$1
       (i32.const 100)
@@ -157,4 +157,34 @@
    (f64.const 4776014875438170098655851e156)
   )
  )
+ (func $refinalize-two-breaks-one-unreachable (type $2)
+  (drop
+   (block $label$0 (result i64)
+    (br_if $label$0
+     (select
+      (i64.const 1)
+      (block $block
+       (set_global $global$0
+        (i32.const 1)
+       )
+       (br $label$0
+        (i64.const -22)
+       )
+      )
+      (i32.const 0)
+     )
+     (i32.const 1)
+    )
+   )
+  )
+ )
+ (func $one-break-value-and-it-is-unreachable (type $3) (result f64)
+  (local $var$0 i32)
+  (block $label$6 (result f64)
+   (br_if $label$6
+    (unreachable)
+    (i32.const 0)
+   )
+  )
+ )
 )
diff --git a/test/passes/precompute.wast b/test/passes/precompute.wast
index 3eb2683bf..b339a55d4 100644
--- a/test/passes/precompute.wast
+++ b/test/passes/precompute.wast
@@ -249,4 +249,35 @@
     (f64.const 4776014875438170098655851e156)
    )
   )
+  (func $refinalize-two-breaks-one-unreachable
+   (drop
+    (block $label$0 (result i64)
+     (br_if $label$0
+      (select
+       (i64.const 1)
+       (block (result i64)
+        (set_global $global$0
+         (i32.const 1)
+        )
+        (br_if $label$0
+         (i64.const -22)
+         (i32.const -1)
+        )
+       )
+       (i32.const 0)
+      )
+      (i32.const 1)
+     )
+    )
+   )
+  )
+  (func $one-break-value-and-it-is-unreachable (result f64)
+   (local $var$0 i32)
+   (block $label$6 (result f64)
+    (br_if $label$6
+     (unreachable)
+     (i32.const 0)
+    )
+   )
+  )
 )
diff --git a/test/passes/remove-unused-brs.txt b/test/passes/remove-unused-brs.txt
index 7951cf18f..6991680f7 100644
--- a/test/passes/remove-unused-brs.txt
+++ b/test/passes/remove-unused-brs.txt
@@ -332,7 +332,7 @@
     )
    )
    (if
-    (block $block6
+    (block $block6 (result i32)
      (block $block15
       (drop
        (i32.const 2)
@@ -1037,11 +1037,23 @@
    )
   )
  )
- (func $untaken-br-with-concrete-last-element (type $2) (result i32)
-  (block $label$8 (result i32)
-   (block $label$11 (result i32)
+ (func $untaken-br-with-concrete-last-element (type $1)
+  (block $label$8
+   (block $label$11
     (block $label$14
      (br_if $label$8
+      (br $label$8)
+     )
+    )
+   )
+  )
+ )
+ (func $untaken-br-with-concrete-last-element2 (type $2) (result i32)
+  (block $label$8 (result i32)
+   (block $label$11 (result i32)
+    (block $label$14 (result i32)
+     (br_if $label$14
+      (i32.const 102)
       (br $label$11
        (i32.const 103)
       )
@@ -1062,25 +1074,29 @@
   )
  )
  (func $unreachable-if-that-could-be-a-br_if (type $7) (result i64)
-  (loop $label$3
-   (if
-    (unreachable)
-    (f64.const 1)
-    (br $label$3)
+  (loop $label$3 (result i64)
+   (drop
+    (if (result f64)
+     (unreachable)
+     (f64.const 1)
+     (br $label$3)
+    )
    )
    (i64.const 1)
   )
  )
  (func $nop-br-might-update-type (type $1)
   (block $label$39
-   (if
-    (unreachable)
+   (drop
     (if (result i32)
-     (i32.const 1)
-     (br $label$39)
+     (unreachable)
+     (if (result i32)
+      (i32.const 1)
+      (br $label$39)
+      (i32.const 0)
+     )
      (i32.const 0)
     )
-    (i32.const 0)
    )
   )
  )
diff --git a/test/passes/remove-unused-brs.wast b/test/passes/remove-unused-brs.wast
index 20441d9e4..5c6776226 100644
--- a/test/passes/remove-unused-brs.wast
+++ b/test/passes/remove-unused-brs.wast
@@ -919,11 +919,24 @@
     )
    )
   )
-  (func $untaken-br-with-concrete-last-element (result i32)
+  (func $untaken-br-with-concrete-last-element
+   (block $label$8
+    (block $label$11
+     (block $label$14
+      (br_if $label$14
+       (br $label$11
+       )
+      )
+     )
+    )
+   )
+  )
+  (func $untaken-br-with-concrete-last-element2 (result i32)
    (block $label$8 (result i32)
     (block $label$11 (result i32)
-     (block $label$14
+     (block $label$14 (result i32)
       (br_if $label$14
+       (i32.const 102)
        (br $label$11
         (i32.const 103)
        )
@@ -944,25 +957,29 @@
    )
   )
   (func $unreachable-if-that-could-be-a-br_if (result i64)
-   (loop $label$3
-    (if
-     (unreachable)
-     (f64.const 1)
-     (br $label$3)
+   (loop $label$3 (result i64)
+    (drop
+     (if (result f64)
+      (unreachable)
+      (f64.const 1)
+      (br $label$3)
+     )
     )
     (i64.const 1)
    )
   )
   (func $nop-br-might-update-type
    (block $label$39
-    (if
-     (unreachable)
+    (drop
      (if (result i32)
-      (i32.const 1)
-      (br $label$39) ;; if we nop this, then the parent type must change
+      (unreachable)
+      (if (result i32)
+       (i32.const 1)
+       (br $label$39) ;; if we nop this, then the parent type must change
+       (i32.const 0)
+      )
       (i32.const 0)
      )
-     (i32.const 0)
     )
    )
   )
diff --git a/test/passes/remove-unused-names.txt b/test/passes/remove-unused-names.txt
index 894e07165..6fd0f4e51 100644
--- a/test/passes/remove-unused-names.txt
+++ b/test/passes/remove-unused-names.txt
@@ -66,15 +66,13 @@
  )
  (func $merge-typed-with-unreachable-child (type $2) (result i32)
   (local $0 f32)
-  (block $label$0 (result i32)
-   (block $label$1
+  (block $label$1 (result i32)
+   (br_if $label$1
+    (i32.const 1)
     (br_if $label$1
      (i32.const 0)
-     (br_if $label$0
+     (br $label$1
       (i32.const 0)
-      (br $label$0
-       (i32.const 0)
-      )
      )
     )
    )
diff --git a/test/passes/remove-unused-names.wast b/test/passes/remove-unused-names.wast
index dc882cf4c..a4c240f02 100644
--- a/test/passes/remove-unused-names.wast
+++ b/test/passes/remove-unused-names.wast
@@ -80,9 +80,9 @@
   (func $merge-typed-with-unreachable-child (result i32)
    (local $0 f32)
    (block $label$0 (result i32)
-    (block $label$1
+    (block $label$1 (result i32)
      (br_if $label$1
-      (i32.const 0)
+      (i32.const 1)
       (br_if $label$0
        (i32.const 0)
        (br $label$0
diff --git a/test/passes/remove-unused-names_merge-blocks.txt b/test/passes/remove-unused-names_merge-blocks.txt
index 19f03c662..c170a6c99 100644
--- a/test/passes/remove-unused-names_merge-blocks.txt
+++ b/test/passes/remove-unused-names_merge-blocks.txt
@@ -853,9 +853,11 @@
   (unreachable)
  )
  (func $concrete_finale_in_unreachable (type $5) (result f64)
-  (unreachable)
   (drop
-   (f64.const 6.322092475576799e-96)
+   (block (result f64)
+    (unreachable)
+    (f64.const 6.322092475576799e-96)
+   )
   )
   (f64.const -1)
  )
@@ -897,7 +899,7 @@
  )
  (func $drop-unreachable-block-with-concrete-final (type $3)
   (drop
-   (block
+   (block (result i32)
     (drop
      (block
       (drop
diff --git a/test/passes/remove-unused-names_merge-blocks.wast b/test/passes/remove-unused-names_merge-blocks.wast
index 6f6dd92b9..67a1f2762 100644
--- a/test/passes/remove-unused-names_merge-blocks.wast
+++ b/test/passes/remove-unused-names_merge-blocks.wast
@@ -1007,9 +1007,11 @@
  )
  (func $concrete_finale_in_unreachable (result f64)
   (block $label$0 (result f64)
-   (block ;; this block is unreachable
-    (unreachable)
-    (f64.const 6.322092475576799e-96)
+   (drop
+    (block (result f64)
+     (unreachable)
+     (f64.const 6.322092475576799e-96)
+    )
    )
    (f64.const -1)
   )
@@ -1056,7 +1058,7 @@
  )
  (func $drop-unreachable-block-with-concrete-final
   (drop
-   (block
+   (block (result i32)
     (drop
      (block
       (drop
@@ -1070,7 +1072,7 @@
  )
  (func $merging-with-unreachable-in-middle (result i32)
   (block $label$1 (result i32)
-   (block
+   (block (result i32)
     (return
      (i32.const 21536)
     )
diff --git a/test/passes/simplify-locals.txt b/test/passes/simplify-locals.txt
index 39fc1d97d..15d8b21e5 100644
--- a/test/passes/simplify-locals.txt
+++ b/test/passes/simplify-locals.txt
@@ -877,17 +877,13 @@
   )
  )
  (func $if-return-but-unreachable (type $10) (param $var$0 i64)
-  (tee_local $var$0
-   (if
-    (unreachable)
-    (block (result i64)
-     (nop)
-     (get_local $var$0)
-    )
-    (block (result i64)
-     (nop)
-     (i64.const 1)
-    )
+  (if
+   (unreachable)
+   (set_local $var$0
+    (get_local $var$0)
+   )
+   (set_local $var$0
+    (i64.const 1)
    )
   )
  )
diff --git a/test/passes/vacuum.txt b/test/passes/vacuum.txt
index 011fb99f5..b254179cd 100644
--- a/test/passes/vacuum.txt
+++ b/test/passes/vacuum.txt
@@ -223,7 +223,7 @@
   )
  )
  (func $leave-block-even-if-br-not-taken (type $6) (result f64)
-  (block $label$0
+  (block $label$0 (result f64)
    (f64.store align=1
     (i32.const 879179022)
     (br_if $label$0
@@ -276,12 +276,11 @@
  (func $unreachable-if-with-nop-arm-that-leaves-a-concrete-value-if-nop-is-removed (type $0)
   (block $label$0
    (loop $label$1
-    (br_if $label$0
-     (i32.load8_s
-      (i32.const 1634541608)
-     )
-     (loop $label$9
-      (br $label$9)
+    (drop
+     (br_if $label$0
+      (loop $label$9
+       (br $label$9)
+      )
      )
     )
    )
diff --git a/test/passes/vacuum.wast b/test/passes/vacuum.wast
index 3b5b22e9c..dbbffee41 100644
--- a/test/passes/vacuum.wast
+++ b/test/passes/vacuum.wast
@@ -502,7 +502,7 @@
    (local $2 i32)
    (block $label$0
     (drop
-     (block
+     (block (result i32)
       (br $label$0)
       (get_local $2)
      )
@@ -596,17 +596,16 @@
   (func $unreachable-if-with-nop-arm-that-leaves-a-concrete-value-if-nop-is-removed
    (block $label$0
     (loop $label$1
-     (if
-      (br_if $label$0
-       (i32.load8_s
-        (i32.const 1634541608)
-       )
-       (loop $label$9
-        (br $label$9)
+     (drop
+      (if (result i32)
+       (br_if $label$0
+        (loop $label$9
+         (br $label$9)
+        )
        )
+       (unreachable)
+       (i32.const 1920103026)
       )
-      (nop)
-      (i32.const 1920103026)
      )
     )
    )