wasm-decompile: added precedence support. (#1277)

Previously it would simply bracket all binary exps. Now it has a
precedence system that is in line with what people know from most
programming languages.

3 files changed, 50 insertions, 3 deletions

diff --git a/test/decompile/basic.txt b/test/decompile/basic.txt
index 90665103..ebb5dd46 100644
--- a/test/decompile/basic.txt
+++ b/test/decompile/basic.txt
@@ -82,7 +82,7 @@ export function f(a:int, b:int):int {
   var c:long = 8L;
   var d:float = 6.0f;
   var e:double = 7.0;
-  if (e < 10.0) { 1[4]:int = (2[3]:int + 5) }
+  if (e < 10.0) { 1[4]:int = 2[3]:int + 5 }
   f(a + g_b, 9);
   loop L_b {
     block B_c {
diff --git a/test/decompile/loadstore.txt b/test/decompile/loadstore.txt
index 0a6cf58d..d1216950 100644
--- a/test/decompile/loadstore.txt
+++ b/test/decompile/loadstore.txt
@@ -69,8 +69,8 @@ export function f(a:{ a:float, b:float }, b:{ a:ushort, b:long }) {
   var f:int;
   var g:int;
   var h:int;
-  (a.a + c.a) + (a.b + c.b);
-  (b.a + d.a) + (b.b + d.b);
+  a.a + c.a + a.b + c.b;
+  b.a + d.a + b.b + d.b;
   e[0]:int;
   e[0]:float;
   f[0]:int;
diff --git a/test/decompile/precedence.txt b/test/decompile/precedence.txt
new file mode 100644
index 00000000..8980255a
--- /dev/null
+++ b/test/decompile/precedence.txt
@@ -0,0 +1,47 @@
+  ;;; TOOL: run-wasm-decompile
+
+(module
+  (memory $m1 1)
+
+  (func $precedence (param) (result)
+    ;; some exp in order that will generate no parens
+    i32.const 0
+    i32.load offset=0
+    i32.const 1
+    i32.mul
+    i32.const 2
+    i32.add
+    i32.const 3
+    i32.shl
+    i32.const 4
+    i32.eq
+    i32.const 5
+    i32.and
+    drop
+    ;; some exp in reverse order that will generate parens.
+    i32.const 6
+    i32.const 5
+    i32.and
+    i32.const 4
+    i32.eq
+    i32.const 3
+    i32.shl
+    i32.const 2
+    i32.add
+    i32.const 1
+    i32.mul
+    i32.load offset=0
+    drop
+  )
+  (export "precedence" (func $precedence))
+)
+
+(;; STDOUT ;;;
+memory M_a(initial: 1, max: 0);
+
+export function precedence() {
+  0[0]:int * 1 + 2 << 3 == 4 & 5;
+  (((((6 & 5) == 4) << 3) + 2) * 1)[0]:int;
+}
+
+;;; STDOUT ;;)