wasm2js: more js optimization (#2050)

* Emit ints as signed, so -1 isn't a big unsigned number.
* x - -c (where c is a constant) is larger than x + c in js (but not wasm)
* +(+x) => +x
* Avoid unnecessary coercions on calls, return, load, etc. - we just need coercions when entering or exiting "wasm" (not internally), and on actual operations that need them.

1 files changed, 20 insertions, 43 deletions

diff --git a/test/wasm2js/f32.2asm.js b/test/wasm2js/f32.2asm.js
index 62ea4db91..a6c7d182b 100644
--- a/test/wasm2js/f32.2asm.js
+++ b/test/wasm2js/f32.2asm.js
@@ -96,12 +96,12 @@ function asmFunc(global, env, buffer) {
  
  function $9(x) {
   x = Math_fround(x);
-  return Math_fround(Math_fround(__wasm_trunc_f32(Math_fround(x))));
+  return Math_fround(__wasm_trunc_f32(x));
  }
  
  function $10(x) {
   x = Math_fround(x);
-  return Math_fround(Math_fround(__wasm_nearest_f32(Math_fround(x))));
+  return Math_fround(__wasm_nearest_f32(x));
  }
  
  function $11(x) {
@@ -117,88 +117,66 @@ function asmFunc(global, env, buffer) {
  function $13(x, y) {
   x = Math_fround(x);
   y = Math_fround(y);
-  return Math_fround((wasm2js_scratch_store_i32(0, (wasm2js_scratch_store_f32(x), wasm2js_scratch_load_i32(0)) & 2147483647 | (wasm2js_scratch_store_f32(y), wasm2js_scratch_load_i32(0)) & 2147483648), wasm2js_scratch_load_f32()));
+  return Math_fround((wasm2js_scratch_store_i32(0, (wasm2js_scratch_store_f32(x), wasm2js_scratch_load_i32(0)) & 2147483647 | (wasm2js_scratch_store_f32(y), wasm2js_scratch_load_i32(0)) & -2147483648), wasm2js_scratch_load_f32()));
  }
  
  function legalstub$0($0_1, $1_1) {
-  $0_1 = +$0_1;
-  $1_1 = +$1_1;
-  return +(+Math_fround($0(Math_fround(Math_fround($0_1)), Math_fround(Math_fround($1_1)))));
+  return +$0(Math_fround($0_1), Math_fround($1_1));
  }
  
  function legalstub$1($0_1, $1_1) {
-  $0_1 = +$0_1;
-  $1_1 = +$1_1;
-  return +(+Math_fround($1(Math_fround(Math_fround($0_1)), Math_fround(Math_fround($1_1)))));
+  return +$1(Math_fround($0_1), Math_fround($1_1));
  }
  
  function legalstub$2($0_1, $1_1) {
-  $0_1 = +$0_1;
-  $1_1 = +$1_1;
-  return +(+Math_fround($2(Math_fround(Math_fround($0_1)), Math_fround(Math_fround($1_1)))));
+  return +$2(Math_fround($0_1), Math_fround($1_1));
  }
  
  function legalstub$3($0_1, $1_1) {
-  $0_1 = +$0_1;
-  $1_1 = +$1_1;
-  return +(+Math_fround($3(Math_fround(Math_fround($0_1)), Math_fround(Math_fround($1_1)))));
+  return +$3(Math_fround($0_1), Math_fround($1_1));
  }
  
  function legalstub$4($0_1) {
-  $0_1 = +$0_1;
-  return +(+Math_fround($4(Math_fround(Math_fround($0_1)))));
+  return +$4(Math_fround($0_1));
  }
  
  function legalstub$5($0_1, $1_1) {
-  $0_1 = +$0_1;
-  $1_1 = +$1_1;
-  return +(+Math_fround($5(Math_fround(Math_fround($0_1)), Math_fround(Math_fround($1_1)))));
+  return +$5(Math_fround($0_1), Math_fround($1_1));
  }
  
  function legalstub$6($0_1, $1_1) {
-  $0_1 = +$0_1;
-  $1_1 = +$1_1;
-  return +(+Math_fround($6(Math_fround(Math_fround($0_1)), Math_fround(Math_fround($1_1)))));
+  return +$6(Math_fround($0_1), Math_fround($1_1));
  }
  
  function legalstub$7($0_1) {
-  $0_1 = +$0_1;
-  return +(+Math_fround($7(Math_fround(Math_fround($0_1)))));
+  return +$7(Math_fround($0_1));
  }
  
  function legalstub$8($0_1) {
-  $0_1 = +$0_1;
-  return +(+Math_fround($8(Math_fround(Math_fround($0_1)))));
+  return +$8(Math_fround($0_1));
  }
  
  function legalstub$9($0_1) {
-  $0_1 = +$0_1;
-  return +(+Math_fround($9(Math_fround(Math_fround($0_1)))));
+  return +$9(Math_fround($0_1));
  }
  
  function legalstub$10($0_1) {
-  $0_1 = +$0_1;
-  return +(+Math_fround($10(Math_fround(Math_fround($0_1)))));
+  return +$10(Math_fround($0_1));
  }
  
  function legalstub$11($0_1) {
-  $0_1 = +$0_1;
-  return +(+Math_fround($11(Math_fround(Math_fround($0_1)))));
+  return +$11(Math_fround($0_1));
  }
  
  function legalstub$12($0_1) {
-  $0_1 = +$0_1;
-  return +(+Math_fround($12(Math_fround(Math_fround($0_1)))));
+  return +$12(Math_fround($0_1));
  }
  
  function legalstub$13($0_1, $1_1) {
-  $0_1 = +$0_1;
-  $1_1 = +$1_1;
-  return +(+Math_fround($13(Math_fround(Math_fround($0_1)), Math_fround(Math_fround($1_1)))));
+  return +$13(Math_fround($0_1), Math_fround($1_1));
  }
  
  function __wasm_nearest_f32(var$0) {
-  var$0 = Math_fround(var$0);
   var var$1 = Math_fround(0), var$2 = Math_fround(0), wasm2js_f32$0 = Math_fround(0), wasm2js_f32$1 = Math_fround(0), wasm2js_i32$0 = 0;
   var$1 = Math_fround(Math_floor(var$0));
   var$2 = Math_fround(var$0 - var$1);
@@ -206,19 +184,18 @@ function asmFunc(global, env, buffer) {
    {
     var$0 = Math_fround(Math_ceil(var$0));
     if (var$2 > Math_fround(.5)) {
-     return Math_fround(var$0)
+     return var$0
     }
     var$2 = Math_fround(var$1 * Math_fround(.5));
     var$1 = (wasm2js_f32$0 = var$1, wasm2js_f32$1 = var$0, wasm2js_i32$0 = Math_fround(var$2 - Math_fround(Math_floor(var$2))) == Math_fround(0.0), wasm2js_i32$0 ? wasm2js_f32$0 : wasm2js_f32$1);
    }
   }
-  return Math_fround(var$1);
+  return var$1;
  }
  
  function __wasm_trunc_f32(var$0) {
-  var$0 = Math_fround(var$0);
   var wasm2js_f32$0 = Math_fround(0), wasm2js_f32$1 = Math_fround(0), wasm2js_i32$0 = 0;
-  return Math_fround((wasm2js_f32$0 = Math_fround(Math_ceil(var$0)), wasm2js_f32$1 = Math_fround(Math_floor(var$0)), wasm2js_i32$0 = var$0 < Math_fround(0.0), wasm2js_i32$0 ? wasm2js_f32$0 : wasm2js_f32$1));
+  return wasm2js_f32$0 = Math_fround(Math_ceil(var$0)), wasm2js_f32$1 = Math_fround(Math_floor(var$0)), wasm2js_i32$0 = var$0 < Math_fround(0.0), wasm2js_i32$0 ? wasm2js_f32$0 : wasm2js_f32$1;
  }
  
  var FUNCTION_TABLE = [];