SSA pass (#1049)

 * Add SSA pass which ensures a single assign for each local, except for merged locals where we ensure exactly a single assign from one of the paths leading to that use

 * Also add InstrumentLocals pass, useful for debugging locals (similar to InstrumentMemory but for locals)

 * Fix a PickLoadSigns bug with tees not being ignored, which was not noticed until now because we ran it on flatter output by default, but the ssa pass uncovered the bug

6 files changed, 1188 insertions, 0 deletions

diff --git a/test/passes/instrument-locals.txt b/test/passes/instrument-locals.txt
new file mode 100644
index 000000000..5cc8a98fe
--- /dev/null
+++ b/test/passes/instrument-locals.txt
@@ -0,0 +1,118 @@
+(module
+ (type $0 (func))
+ (type $FUNCSIG$iiii (func (param i32 i32 i32) (result i32)))
+ (type $FUNCSIG$jiij (func (param i32 i32 i64) (result i64)))
+ (type $FUNCSIG$fiif (func (param i32 i32 f32) (result f32)))
+ (type $FUNCSIG$diid (func (param i32 i32 f64) (result f64)))
+ (import "instrument" "get_i32" (func $get_i32 (param i32 i32 i32) (result i32)))
+ (import "instrument" "get_i64" (func $get_i64 (param i32 i32 i64) (result i64)))
+ (import "instrument" "get_f32" (func $get_f32 (param i32 i32 f32) (result f32)))
+ (import "instrument" "get_f64" (func $get_f64 (param i32 i32 f64) (result f64)))
+ (import "instrument" "set_i32" (func $set_i32 (param i32 i32 i32) (result i32)))
+ (import "instrument" "set_i64" (func $set_i64 (param i32 i32 i64) (result i64)))
+ (import "instrument" "set_f32" (func $set_f32 (param i32 i32 f32) (result f32)))
+ (import "instrument" "set_f64" (func $set_f64 (param i32 i32 f64) (result f64)))
+ (memory $0 0)
+ (func $A (type $0)
+  (local $x i32)
+  (local $y i64)
+  (local $z f32)
+  (local $w f64)
+  (drop
+   (call $get_i32
+    (i32.const 0)
+    (i32.const 0)
+    (get_local $x)
+   )
+  )
+  (drop
+   (get_local $y)
+  )
+  (drop
+   (call $get_f32
+    (i32.const 1)
+    (i32.const 2)
+    (get_local $z)
+   )
+  )
+  (drop
+   (call $get_f64
+    (i32.const 2)
+    (i32.const 3)
+    (get_local $w)
+   )
+  )
+  (drop
+   (call $get_i32
+    (i32.const 3)
+    (i32.const 0)
+    (get_local $x)
+   )
+  )
+  (drop
+   (get_local $y)
+  )
+  (drop
+   (call $get_f32
+    (i32.const 4)
+    (i32.const 2)
+    (get_local $z)
+   )
+  )
+  (drop
+   (call $get_f64
+    (i32.const 5)
+    (i32.const 3)
+    (get_local $w)
+   )
+  )
+  (set_local $x
+   (call $set_i32
+    (i32.const 6)
+    (i32.const 0)
+    (i32.const 1)
+   )
+  )
+  (set_local $y
+   (i64.const 2)
+  )
+  (set_local $z
+   (call $set_f32
+    (i32.const 7)
+    (i32.const 2)
+    (f32.const 3.2100000381469727)
+   )
+  )
+  (set_local $w
+   (call $set_f64
+    (i32.const 8)
+    (i32.const 3)
+    (f64.const 4.321)
+   )
+  )
+  (set_local $x
+   (call $set_i32
+    (i32.const 9)
+    (i32.const 0)
+    (i32.const 11)
+   )
+  )
+  (set_local $y
+   (i64.const 22)
+  )
+  (set_local $z
+   (call $set_f32
+    (i32.const 10)
+    (i32.const 2)
+    (f32.const 33.209999084472656)
+   )
+  )
+  (set_local $w
+   (call $set_f64
+    (i32.const 11)
+    (i32.const 3)
+    (f64.const 44.321)
+   )
+  )
+ )
+)
diff --git a/test/passes/instrument-locals.wast b/test/passes/instrument-locals.wast
new file mode 100644
index 000000000..b7e34c6d6
--- /dev/null
+++ b/test/passes/instrument-locals.wast
@@ -0,0 +1,29 @@
+(module
+  (func $A
+    (local $x i32)
+    (local $y i64)
+    (local $z f32)
+    (local $w f64)
+
+    (drop (get_local $x))
+    (drop (get_local $y))
+    (drop (get_local $z))
+    (drop (get_local $w))
+
+    (drop (get_local $x))
+    (drop (get_local $y))
+    (drop (get_local $z))
+    (drop (get_local $w))
+
+    (set_local $x (i32.const 1))
+    (set_local $y (i64.const 2))
+    (set_local $z (f32.const 3.21))
+    (set_local $w (f64.const 4.321))
+
+    (set_local $x (i32.const 11))
+    (set_local $y (i64.const 22))
+    (set_local $z (f32.const 33.21))
+    (set_local $w (f64.const 44.321))
+  )
+)
+
diff --git a/test/passes/pick-load-signs.txt b/test/passes/pick-load-signs.txt
index 707bb50e9..e8507fa29 100644
--- a/test/passes/pick-load-signs.txt
+++ b/test/passes/pick-load-signs.txt
@@ -260,4 +260,20 @@
    (i32.const 1024)
   )
  )
+ (func $tees (type $0)
+  (local $y i32)
+  (drop
+   (tee_local $y
+    (i32.load8_s
+     (i32.const 1024)
+    )
+   )
+  )
+  (drop
+   (i32.and
+    (get_local $y)
+    (i32.const 255)
+   )
+  )
+ )
 )
diff --git a/test/passes/pick-load-signs.wast b/test/passes/pick-load-signs.wast
index 49105e497..33f814926 100644
--- a/test/passes/pick-load-signs.wast
+++ b/test/passes/pick-load-signs.wast
@@ -257,4 +257,20 @@
       (i32.const 1024)
     )
   )
+  (func $tees
+    (local $y i32)
+    (drop ;; a "use", so we can't alter the value
+      (tee_local $y
+        (i32.load8_s
+          (i32.const 1024)
+        )
+      )
+    )
+    (drop
+      (i32.and
+        (get_local $y)
+        (i32.const 255)
+      )
+    )
+  )
 )
diff --git a/test/passes/ssa.txt b/test/passes/ssa.txt
new file mode 100644
index 000000000..3d410057c
--- /dev/null
+++ b/test/passes/ssa.txt
@@ -0,0 +1,694 @@
+(module
+ (type $0 (func (param i32)))
+ (type $1 (func))
+ (memory $0 0)
+ (func $basics (type $0) (param $x i32)
+  (local $y i32)
+  (local $z f32)
+  (local $w i64)
+  (local $t f64)
+  (local $5 i32)
+  (local $6 f64)
+  (local $7 f64)
+  (drop
+   (get_local $x)
+  )
+  (drop
+   (i32.const 0)
+  )
+  (drop
+   (f32.const 0)
+  )
+  (drop
+   (i64.const 0)
+  )
+  (drop
+   (f64.const 0)
+  )
+  (set_local $5
+   (i32.const 100)
+  )
+  (drop
+   (get_local $5)
+  )
+  (set_local $6
+   (f64.const 2)
+  )
+  (drop
+   (get_local $6)
+  )
+  (set_local $7
+   (f64.const 33)
+  )
+  (drop
+   (get_local $7)
+  )
+  (drop
+   (get_local $7)
+  )
+ )
+ (func $if (type $0) (param $p i32)
+  (local $x i32)
+  (local $y i32)
+  (local $3 i32)
+  (local $4 i32)
+  (local $5 i32)
+  (local $6 i32)
+  (local $7 i32)
+  (local $8 i32)
+  (local $9 i32)
+  (local $10 i32)
+  (local $11 i32)
+  (local $12 i32)
+  (local $13 i32)
+  (local $14 i32)
+  (local $15 i32)
+  (local $16 i32)
+  (local $17 i32)
+  (set_local $13
+   (get_local $p)
+  )
+  (block
+   (drop
+    (if i32
+     (i32.const 1)
+     (i32.const 0)
+     (i32.const 0)
+    )
+   )
+   (if
+    (i32.const 1)
+    (set_local $3
+     (tee_local $15
+      (tee_local $14
+       (tee_local $12
+        (i32.const 1)
+       )
+      )
+     )
+    )
+   )
+   (drop
+    (get_local $12)
+   )
+   (if
+    (i32.const 1)
+    (set_local $4
+     (tee_local $13
+      (i32.const 1)
+     )
+    )
+   )
+   (drop
+    (get_local $13)
+   )
+   (if
+    (i32.const 1)
+    (set_local $5
+     (tee_local $15
+      (tee_local $14
+       (i32.const 2)
+      )
+     )
+    )
+    (nop)
+   )
+   (drop
+    (get_local $14)
+   )
+   (if
+    (i32.const 1)
+    (nop)
+    (set_local $6
+     (tee_local $15
+      (i32.const 3)
+     )
+    )
+   )
+   (drop
+    (get_local $15)
+   )
+   (if
+    (i32.const 1)
+    (set_local $7
+     (tee_local $16
+      (i32.const 4)
+     )
+    )
+    (set_local $8
+     (tee_local $16
+      (i32.const 5)
+     )
+    )
+   )
+   (drop
+    (get_local $16)
+   )
+   (if
+    (i32.const 1)
+    (set_local $9
+     (tee_local $17
+      (i32.const 6)
+     )
+    )
+    (block $block
+     (set_local $10
+      (i32.const 7)
+     )
+     (set_local $11
+      (tee_local $17
+       (i32.const 8)
+      )
+     )
+    )
+   )
+   (drop
+    (get_local $17)
+   )
+  )
+ )
+ (func $if2 (type $0) (param $x i32)
+  (local $1 i32)
+  (local $2 i32)
+  (set_local $2
+   (get_local $x)
+  )
+  (block
+   (if
+    (i32.const 1)
+    (block $block
+     (set_local $1
+      (tee_local $2
+       (i32.const 1)
+      )
+     )
+     (drop
+      (get_local $1)
+     )
+    )
+   )
+   (drop
+    (get_local $2)
+   )
+  )
+ )
+ (func $block (type $0) (param $x i32)
+  (local $1 i32)
+  (local $2 i32)
+  (set_local $2
+   (get_local $x)
+  )
+  (block
+   (block $out
+    (br_if $out
+     (i32.const 2)
+    )
+    (set_local $1
+     (tee_local $2
+      (i32.const 1)
+     )
+    )
+   )
+   (drop
+    (get_local $2)
+   )
+  )
+ )
+ (func $block2 (type $0) (param $x i32)
+  (local $1 i32)
+  (local $2 i32)
+  (local $3 i32)
+  (local $4 i32)
+  (local $5 i32)
+  (local $6 i32)
+  (block $out
+   (set_local $1
+    (tee_local $6
+     (i32.const 1)
+    )
+   )
+   (drop
+    (get_local $1)
+   )
+   (br_if $out
+    (i32.const 2)
+   )
+   (drop
+    (get_local $1)
+   )
+   (if
+    (i32.const 3)
+    (block $block
+     (set_local $2
+      (tee_local $6
+       (i32.const 1)
+      )
+     )
+     (drop
+      (get_local $2)
+     )
+     (br $out)
+    )
+   )
+   (drop
+    (get_local $1)
+   )
+   (set_local $3
+    (tee_local $6
+     (i32.const 4)
+    )
+   )
+   (drop
+    (get_local $3)
+   )
+   (if
+    (i32.const 5)
+    (br $out)
+   )
+   (drop
+    (get_local $3)
+   )
+   (if
+    (i32.const 6)
+    (nop)
+   )
+   (if
+    (i32.const 7)
+    (nop)
+    (nop)
+   )
+   (block $in
+    (set_local $4
+     (tee_local $6
+      (i32.const 8)
+     )
+    )
+    (drop
+     (get_local $4)
+    )
+    (br_table $in $out
+     (i32.const 9)
+    )
+   )
+   (drop
+    (get_local $4)
+   )
+   (block $in2
+    (set_local $5
+     (tee_local $6
+      (i32.const 10)
+     )
+    )
+    (drop
+     (get_local $5)
+    )
+    (br_table $out $in2
+     (i32.const 11)
+    )
+   )
+   (drop
+    (get_local $5)
+   )
+  )
+  (drop
+   (get_local $6)
+  )
+ )
+ (func $loop (type $0) (param $x i32)
+  (local $1 i32)
+  (local $2 i32)
+  (set_local $2
+   (get_local $x)
+  )
+  (block
+   (drop
+    (get_local $x)
+   )
+   (loop $moar
+    (drop
+     (get_local $2)
+    )
+    (set_local $1
+     (tee_local $2
+      (i32.const 1)
+     )
+    )
+    (br_if $moar
+     (i32.const 2)
+    )
+   )
+   (drop
+    (get_local $1)
+   )
+  )
+ )
+ (func $loop2 (type $0) (param $x i32)
+  (local $1 i32)
+  (local $2 i32)
+  (local $3 i32)
+  (local $4 i32)
+  (set_local $4
+   (get_local $x)
+  )
+  (block
+   (drop
+    (get_local $x)
+   )
+   (loop $moar
+    (drop
+     (get_local $4)
+    )
+    (set_local $1
+     (i32.const 1)
+    )
+    (drop
+     (get_local $1)
+    )
+    (set_local $2
+     (tee_local $4
+      (i32.const 123)
+     )
+    )
+    (drop
+     (get_local $2)
+    )
+    (br_if $moar
+     (i32.const 2)
+    )
+    (drop
+     (get_local $2)
+    )
+    (set_local $3
+     (i32.const 3)
+    )
+    (drop
+     (get_local $3)
+    )
+   )
+   (drop
+    (get_local $3)
+   )
+  )
+ )
+ (func $loop2-zeroinit (type $1)
+  (local $x i32)
+  (local $1 i32)
+  (local $2 i32)
+  (local $3 i32)
+  (local $4 i32)
+  (drop
+   (i32.const 0)
+  )
+  (loop $moar
+   (drop
+    (get_local $4)
+   )
+   (set_local $1
+    (i32.const 1)
+   )
+   (drop
+    (get_local $1)
+   )
+   (set_local $2
+    (tee_local $4
+     (i32.const 123)
+    )
+   )
+   (drop
+    (get_local $2)
+   )
+   (br_if $moar
+    (i32.const 2)
+   )
+   (drop
+    (get_local $2)
+   )
+   (set_local $3
+    (i32.const 3)
+   )
+   (drop
+    (get_local $3)
+   )
+  )
+  (drop
+   (get_local $3)
+  )
+ )
+ (func $real-loop (type $0) (param $param i32)
+  (local $loopvar i32)
+  (local $inc i32)
+  (local $3 i32)
+  (local $4 i32)
+  (local $5 i32)
+  (local $6 i32)
+  (set_local $3
+   (tee_local $6
+    (get_local $param)
+   )
+  )
+  (loop $more
+   (block $stop
+    (if
+     (i32.const 1)
+     (br $stop)
+    )
+    (set_local $4
+     (i32.add
+      (get_local $6)
+      (i32.const 1)
+     )
+    )
+    (set_local $5
+     (tee_local $6
+      (get_local $4)
+     )
+    )
+    (br $more)
+   )
+  )
+  (drop
+   (get_local $6)
+  )
+ )
+ (func $real-loop-outblock (type $0) (param $param i32)
+  (local $loopvar i32)
+  (local $inc i32)
+  (local $3 i32)
+  (local $4 i32)
+  (local $5 i32)
+  (local $6 i32)
+  (set_local $3
+   (tee_local $6
+    (get_local $param)
+   )
+  )
+  (block $stop
+   (loop $more
+    (if
+     (i32.const 1)
+     (br $stop)
+    )
+    (set_local $4
+     (i32.add
+      (get_local $6)
+      (i32.const 1)
+     )
+    )
+    (set_local $5
+     (tee_local $6
+      (get_local $4)
+     )
+    )
+    (br $more)
+   )
+  )
+  (drop
+   (get_local $6)
+  )
+ )
+ (func $loop-loop-param (type $0) (param $param i32)
+  (local $1 i32)
+  (local $2 i32)
+  (local $3 i32)
+  (local $4 i32)
+  (set_local $3
+   (get_local $param)
+  )
+  (set_local $4
+   (get_local $param)
+  )
+  (block
+   (loop $loop1
+    (block $out1
+     (if
+      (get_local $3)
+      (br $out1)
+     )
+     (set_local $1
+      (tee_local $4
+       (tee_local $3
+        (i32.const 1)
+       )
+      )
+     )
+     (br $loop1)
+    )
+   )
+   (loop $loop2
+    (block $out2
+     (if
+      (get_local $4)
+      (br $out2)
+     )
+     (set_local $2
+      (tee_local $4
+       (i32.const 2)
+      )
+     )
+     (br $loop2)
+    )
+   )
+  )
+ )
+ (func $loop-loop-param-nomerge (type $0) (param $param i32)
+  (local $1 i32)
+  (local $2 i32)
+  (local $3 i32)
+  (loop $loop1
+   (block $out1
+    (set_local $1
+     (tee_local $3
+      (i32.const 1)
+     )
+    )
+    (if
+     (get_local $1)
+     (br $out1)
+    )
+    (br $loop1)
+   )
+  )
+  (loop $loop2
+   (block $out2
+    (if
+     (get_local $3)
+     (br $out2)
+    )
+    (set_local $2
+     (tee_local $3
+      (i32.const 2)
+     )
+    )
+    (br $loop2)
+   )
+  )
+ )
+ (func $loop-nesting (type $0) (param $x i32)
+  (local $1 i32)
+  (local $2 i32)
+  (local $3 i32)
+  (local $4 i32)
+  (local $5 i32)
+  (set_local $3
+   (get_local $x)
+  )
+  (set_local $4
+   (get_local $x)
+  )
+  (set_local $5
+   (get_local $x)
+  )
+  (block
+   (block $out
+    (loop $loop1
+     (if
+      (get_local $3)
+      (br $out)
+     )
+     (loop $loop2
+      (if
+       (get_local $4)
+       (br $out)
+      )
+      (set_local $1
+       (tee_local $5
+        (tee_local $4
+         (i32.const 1)
+        )
+       )
+      )
+      (br $loop2)
+     )
+     (set_local $2
+      (tee_local $5
+       (tee_local $4
+        (tee_local $3
+         (i32.const 2)
+        )
+       )
+      )
+     )
+     (br $loop1)
+    )
+   )
+   (drop
+    (get_local $5)
+   )
+  )
+ )
+ (func $loop-nesting-2 (type $0) (param $x i32)
+  (local $1 i32)
+  (local $2 i32)
+  (local $3 i32)
+  (local $4 i32)
+  (local $5 i32)
+  (set_local $3
+   (get_local $x)
+  )
+  (set_local $4
+   (get_local $x)
+  )
+  (set_local $5
+   (get_local $x)
+  )
+  (block
+   (block $out
+    (loop $loop1
+     (if
+      (get_local $3)
+      (br $out)
+     )
+     (loop $loop2
+      (if
+       (get_local $4)
+       (br $out)
+      )
+      (set_local $1
+       (tee_local $5
+        (tee_local $4
+         (i32.const 1)
+        )
+       )
+      )
+      (br_if $loop2
+       (i32.const 3)
+      )
+     )
+     (set_local $2
+      (tee_local $5
+       (tee_local $4
+        (tee_local $3
+         (i32.const 2)
+        )
+       )
+      )
+     )
+     (br $loop1)
+    )
+   )
+   (drop
+    (get_local $5)
+   )
+  )
+ )
+)
diff --git a/test/passes/ssa.wast b/test/passes/ssa.wast
new file mode 100644
index 000000000..fe78aecb5
--- /dev/null
+++ b/test/passes/ssa.wast
@@ -0,0 +1,315 @@
+(module
+  (func $basics (param $x i32)
+    (local $y i32)
+    (local $z f32)
+    (local $w i64)
+    (local $t f64)
+    (drop (get_local $x)) ;; keep as param get
+    (drop (get_local $y)) ;; turn into get of 0-init
+    (drop (get_local $z))
+    (drop (get_local $w))
+    (drop (get_local $t))
+    (set_local $x (i32.const 100)) ;; overwrite param
+    (drop (get_local $x)) ;; no longer a param!
+    (set_local $t (f64.const 2)) ;; overwrite local
+    (drop (get_local $t))
+    (set_local $t (f64.const 33)) ;; overwrite local AGAIN
+    (drop (get_local $t))
+    (drop (get_local $t)) ;; use twice
+  )
+  (func $if (param $p i32)
+    (local $x i32)
+    (local $y i32)
+    (drop
+      (if i32
+        (i32.const 1)
+        (get_local $x)
+        (get_local $y)
+      )
+    )
+    (if
+      (i32.const 1)
+      (set_local $x (i32.const 1))
+    )
+    (drop (get_local $x))
+    ;; same but with param
+    (if
+      (i32.const 1)
+      (set_local $p (i32.const 1))
+    )
+    (drop (get_local $p))
+    ;; if-else
+    (if
+      (i32.const 1)
+      (set_local $x (i32.const 2))
+      (nop)
+    )
+    (drop (get_local $x))
+    (if
+      (i32.const 1)
+      (nop)
+      (set_local $x (i32.const 3))
+    )
+    (drop (get_local $x))
+    (if
+      (i32.const 1)
+      (set_local $x (i32.const 4))
+      (set_local $x (i32.const 5))
+    )
+    (drop (get_local $x))
+    (if
+      (i32.const 1)
+      (set_local $x (i32.const 6))
+      (block
+        (set_local $x (i32.const 7))
+        (set_local $x (i32.const 8))
+      )
+    )
+    (drop (get_local $x))
+  )
+  (func $if2 (param $x i32)
+    (if
+      (i32.const 1)
+      (block
+        (set_local $x (i32.const 1))
+        (drop (get_local $x)) ;; use between phi set and use
+      )
+    )
+    (drop (get_local $x))
+  )
+  (func $block (param $x i32)
+    (block $out
+      (br_if $out (i32.const 2))
+      (set_local $x (i32.const 1))
+    )
+    (drop (get_local $x))
+  )
+  (func $block2 (param $x i32)
+    (block $out
+      (set_local $x (i32.const 1))
+      (drop (get_local $x))
+      (br_if $out (i32.const 2))
+      (drop (get_local $x))
+      (if (i32.const 3)
+        (block
+          (set_local $x (i32.const 1))
+          (drop (get_local $x))
+          (br $out)
+        )
+      )
+      (drop (get_local $x))
+      (set_local $x (i32.const 4))
+      (drop (get_local $x))
+      (if (i32.const 5)
+        (br $out)
+      )
+      (drop (get_local $x))
+      (if (i32.const 6)
+        (nop)
+      )
+      (if (i32.const 7)
+        (nop)
+        (nop)
+      )
+      ;; finally, switching
+      (block $in
+        (set_local $x (i32.const 8))
+        (drop (get_local $x))
+        (br_table $in $out (i32.const 9))
+      )
+      (drop (get_local $x))
+      (block $in2
+        (set_local $x (i32.const 10))
+        (drop (get_local $x))
+        (br_table $out $in2 (i32.const 11))
+      )
+      (drop (get_local $x))
+    )
+    (drop (get_local $x))
+  )
+  (func $loop (param $x i32)
+    (drop (get_local $x))
+    (loop $moar
+      (drop (get_local $x))
+      (set_local $x (i32.const 1))
+      (br_if $moar (i32.const 2))
+    )
+    (drop (get_local $x))
+  )
+  (func $loop2 (param $x i32)
+    (drop (get_local $x))
+    (loop $moar
+      (drop (get_local $x))
+      (set_local $x (i32.const 1))
+      (drop (get_local $x))
+      (set_local $x (i32.const 123))
+      (drop (get_local $x))
+      (br_if $moar (i32.const 2))
+      (drop (get_local $x)) ;; add use in loop before it ends, we should update this to the phi
+      (set_local $x (i32.const 3))
+      (drop (get_local $x)) ;; another use, but should *not* be phi'd
+    )
+    (drop (get_local $x))
+  )
+  (func $loop2-zeroinit
+    (local $x i32)
+    (drop (get_local $x))
+    (loop $moar
+      (drop (get_local $x))
+      (set_local $x (i32.const 1))
+      (drop (get_local $x))
+      (set_local $x (i32.const 123))
+      (drop (get_local $x))
+      (br_if $moar (i32.const 2))
+      (drop (get_local $x)) ;; add use in loop before it ends, we should update this to the phi
+      (set_local $x (i32.const 3))
+      (drop (get_local $x)) ;; another use, but should *not* be phi'd
+    )
+    (drop (get_local $x))
+  )
+  (func $real-loop
+    (param $param i32)
+    (local $loopvar i32)
+    (local $inc i32)
+    (set_local $loopvar
+     (get_local $param)
+    )
+    (loop $more
+     (block $stop
+      (if
+       (i32.const 1)
+       (br $stop)
+      )
+      (set_local $inc
+       (i32.add
+        (get_local $loopvar) ;; this var should be written to from before the loop and the inc at the end
+        (i32.const 1)
+       )
+      )
+      (set_local $loopvar
+       (get_local $inc)
+      )
+      (br $more)
+     )
+    )
+    (drop (get_local $loopvar))
+  )
+  (func $real-loop-outblock
+    (param $param i32)
+    (local $loopvar i32)
+    (local $inc i32)
+    (set_local $loopvar
+     (get_local $param)
+    )
+    (block $stop
+     (loop $more
+      (if
+       (i32.const 1)
+       (br $stop)
+      )
+      (set_local $inc
+       (i32.add
+        (get_local $loopvar) ;; this var should be written to from before the loop and the inc at the end
+        (i32.const 1)
+       )
+      )
+      (set_local $loopvar
+       (get_local $inc)
+      )
+      (br $more)
+     )
+    )
+    (drop (get_local $loopvar))
+  )
+  (func $loop-loop-param
+    (param $param i32)
+    (loop $loop1
+      (block $out1
+        (if
+          (get_local $param)
+          (br $out1)
+        )
+        (set_local $param (i32.const 1))
+        (br $loop1)
+      )
+    )
+    (loop $loop2
+      (block $out2
+        (if
+          (get_local $param)
+          (br $out2)
+        )
+        (set_local $param (i32.const 2))
+        (br $loop2)
+      )
+    )
+  )
+  (func $loop-loop-param-nomerge
+    (param $param i32)
+    (loop $loop1
+      (block $out1
+        (set_local $param (i32.const 1))
+        (if
+          (get_local $param)
+          (br $out1)
+        )
+        (br $loop1)
+      )
+    )
+    (loop $loop2
+      (block $out2
+        (if
+          (get_local $param)
+          (br $out2)
+        )
+        (set_local $param (i32.const 2))
+        (br $loop2)
+      )
+    )
+  )
+  (func $loop-nesting
+    (param $x i32)
+    (block $out
+      (loop $loop1
+        (if
+          (get_local $x)
+          (br $out)
+        )
+        (loop $loop2
+          (if
+            (get_local $x)
+            (br $out)
+          )
+          (set_local $x (i32.const 1))
+          (br $loop2)
+        )
+        (set_local $x (i32.const 2))
+        (br $loop1)
+      )
+    )
+    (drop (get_local $x)) ;; can receive from either set, or input param
+  )
+  (func $loop-nesting-2
+    (param $x i32)
+    (block $out
+      (loop $loop1
+        (if
+          (get_local $x)
+          (br $out)
+        )
+        (loop $loop2
+          (if
+            (get_local $x)
+            (br $out)
+          )
+          (set_local $x (i32.const 1))
+          (br_if $loop2 (i32.const 3)) ;; add fallthrough
+        )
+        (set_local $x (i32.const 2))
+        (br $loop1)
+      )
+    )
+    (drop (get_local $x)) ;; can receive from either set, or input param
+  )
+)
+