Add support for multi-value proposal (#861)

Use the `--enable-multi-value` flag to enable.

A lot of code already "worked" with multi-value, and just needed to
remove the restrictions. Most of the other changes are modifying the
callback APIs to be more general, e.g. taking more than 1 result type.

* Types are now stored as the negative values; this works nicely with
  the encoding of inline function types (used for block signatures),
  which are always positive values.
* Remove `BlockSignature` and use `BlockDeclaration` instead, which
  is just a typedef to `FuncSignature`. This allows for explicit or
  implicit type specifications on the block signatures.
* Allow for >1 "keep" values in the DropKeep interpreter instruction

1 files changed, 28 insertions, 0 deletions

diff --git a/test/interp/if-multi.txt b/test/interp/if-multi.txt
new file mode 100644
index 00000000..64881b33
--- /dev/null
+++ b/test/interp/if-multi.txt
@@ -0,0 +1,28 @@
+;;; TOOL: run-interp
+;;; ARGS*: --enable-multi-value
+(module
+  (func (export "if-multi-result") (result i32)
+    i32.const 1
+    if (result i32 f32)
+      i32.const 2
+      f32.const 3
+    else
+      unreachable
+    end
+    i32.trunc_s/f32
+    i32.add)
+
+  (func (export "if-param") (result f32)
+    f32.const 3
+    i32.const 0
+    if (param f32) (result f32)
+      unreachable
+    else
+      f32.const 100
+      f32.add
+    end)
+)
+(;; STDOUT ;;;
+if-multi-result() => i32:5
+if-param() => f32:103.000000
+;;; STDOUT ;;)