[Exceptions] Finish interpreter + optimizer support for try_table. (#6814)

* Add interpreter support for exnref values.
* Fix optimization passes to support try_table.
* Enable the interpreter (but not in V8, see code) on exceptions.

1 files changed, 145 insertions, 0 deletions

diff --git a/test/lit/passes/dce-eh.wast b/test/lit/passes/dce-eh.wast
new file mode 100644
index 000000000..413a278d0
--- /dev/null
+++ b/test/lit/passes/dce-eh.wast
@@ -0,0 +1,145 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+;; RUN: wasm-opt %s --dce -all -S -o - | filecheck %s
+
+;; If either try_table body or any of catch handler is reachable, the whole
+;; try_table construct is reachable.
+(module
+  ;; CHECK:      (tag $e)
+  (tag $e)
+
+  ;; CHECK:      (tag $e-i32 (param i32))
+  (tag $e-i32 (param i32))
+
+  ;; CHECK:      (func $foo (type $0)
+  ;; CHECK-NEXT:  (nop)
+  ;; CHECK-NEXT: )
+  (func $foo)
+
+  ;; CHECK:      (func $try_table_unreachable (type $0)
+  ;; CHECK-NEXT:  (block $catch
+  ;; CHECK-NEXT:   (try_table (catch_all $catch)
+  ;; CHECK-NEXT:    (unreachable)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (call $foo)
+  ;; CHECK-NEXT: )
+  (func $try_table_unreachable
+    (block $catch
+      (try_table (catch_all $catch)
+        (unreachable)
+      )
+    )
+    (call $foo) ;; shouldn't be dce'd
+  )
+
+  ;; CHECK:      (func $catch_unreachable (type $0)
+  ;; CHECK-NEXT:  (block $tryend
+  ;; CHECK-NEXT:   (block $catch
+  ;; CHECK-NEXT:    (try_table (catch_all $catch)
+  ;; CHECK-NEXT:     (br $tryend)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (unreachable)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (call $foo)
+  ;; CHECK-NEXT: )
+  (func $catch_unreachable
+    (block $tryend
+      (block $catch
+        (try_table (catch_all $catch)
+          (br $tryend)
+        )
+      )
+      (unreachable)
+    )
+    (call $foo) ;; shouldn't be dce'd
+  )
+
+  ;; CHECK:      (func $both_unreachable (type $0)
+  ;; CHECK-NEXT:  (block $tryend
+  ;; CHECK-NEXT:   (block $catch
+  ;; CHECK-NEXT:    (try_table (catch_all $catch)
+  ;; CHECK-NEXT:     (unreachable)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (unreachable)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $both_unreachable
+    (block $tryend
+      (block $catch
+        (try_table (catch_all $catch)
+          (unreachable)
+        )
+      )
+      (unreachable)
+    )
+    (call $foo) ;; should be dce'd
+  )
+
+  ;; CHECK:      (func $throw (type $0)
+  ;; CHECK-NEXT:  (block $label$0
+  ;; CHECK-NEXT:   (block $label$1
+  ;; CHECK-NEXT:    (throw $e)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $throw
+    ;; All these wrapping expressions before 'throw' will be dce'd.
+    (drop
+      (block $label$0 (result externref)
+        (if
+          (i32.clz
+            (block $label$1 (result i32)
+              (throw $e)
+            )
+          )
+          (then
+            (nop)
+          )
+        )
+        (ref.null extern)
+      )
+    )
+  )
+
+  ;; CHECK:      (func $throw_ref (type $0)
+  ;; CHECK-NEXT:  (local $ex exnref)
+  ;; CHECK-NEXT:  (block $tryend
+  ;; CHECK-NEXT:   (local.set $ex
+  ;; CHECK-NEXT:    (block $catch (result exnref)
+  ;; CHECK-NEXT:     (try_table (catch_all_ref $catch)
+  ;; CHECK-NEXT:      (br $tryend)
+  ;; CHECK-NEXT:     )
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (block
+  ;; CHECK-NEXT:    (drop
+  ;; CHECK-NEXT:     (i32.const 0)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (throw_ref
+  ;; CHECK-NEXT:     (local.get $ex)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $throw_ref
+    (local $ex exnref)
+    (block $tryend
+      (local.set $ex
+        (block $catch (result exnref)
+          (try_table (catch_all_ref $catch)
+            (br $tryend)
+          )
+        )
+      )
+      (drop
+        ;; This i32.add will be dce'd.
+        (i32.add
+          (i32.const 0)
+          (throw_ref (local.get $ex))
+        )
+      )
+    )
+  )
+)