wasm2js: ignore implicit traps (#2079)

We don't actually try to emit traps for loads, stores, invalid float to ints, etc., so when optimizing we may as well do so under the assumption those traps do not exist.

This lets us emit nice code for a select whose operands are loads, for example - otherwise, the values seem to have side effects.

5 files changed, 29 insertions, 56 deletions

diff --git a/test/wasm2js/conversions-modified.2asm.js.opt b/test/wasm2js/conversions-modified.2asm.js.opt
index 1f1fd7ac5..2a28ceeba 100644
--- a/test/wasm2js/conversions-modified.2asm.js.opt
+++ b/test/wasm2js/conversions-modified.2asm.js.opt
@@ -76,36 +76,14 @@ function asmFunc(global, env, buffer) {
  
  function $7($0) {
   $0 = Math_fround($0);
-  var $1 = 0, $2 = 0;
-  $2 = ~~$0 >>> 0;
-  if (Math_fround(Math_abs($0)) >= Math_fround(1.0)) {
-   if ($0 > Math_fround(0.0)) {
-    $1 = ~~Math_fround(Math_min(Math_fround(Math_floor(Math_fround($0 / Math_fround(4294967296.0)))), Math_fround(4294967296.0))) >>> 0
-   } else {
-    $1 = ~~Math_fround(Math_ceil(Math_fround(Math_fround($0 - Math_fround(~~$0 >>> 0 >>> 0)) / Math_fround(4294967296.0)))) >>> 0
-   }
-  } else {
-   $1 = 0
-  }
-  i64toi32_i32$HIGH_BITS = $1;
-  return $2 | 0;
+  i64toi32_i32$HIGH_BITS = Math_fround(Math_abs($0)) >= Math_fround(1.0) ? ($0 > Math_fround(0.0) ? ~~Math_fround(Math_min(Math_fround(Math_floor(Math_fround($0 / Math_fround(4294967296.0)))), Math_fround(4294967296.0))) >>> 0 : ~~Math_fround(Math_ceil(Math_fround(Math_fround($0 - Math_fround(~~$0 >>> 0 >>> 0)) / Math_fround(4294967296.0)))) >>> 0) : 0;
+  return ~~$0 >>> 0;
  }
  
  function $9($0) {
   $0 = +$0;
-  var $1 = 0, $2 = 0;
-  $2 = ~~$0 >>> 0;
-  if (Math_abs($0) >= 1.0) {
-   if ($0 > 0.0) {
-    $1 = ~~Math_min(Math_floor($0 / 4294967296.0), 4294967295.0) >>> 0
-   } else {
-    $1 = ~~Math_ceil(($0 - +(~~$0 >>> 0 >>> 0)) / 4294967296.0) >>> 0
-   }
-  } else {
-   $1 = 0
-  }
-  i64toi32_i32$HIGH_BITS = $1;
-  return $2 | 0;
+  i64toi32_i32$HIGH_BITS = Math_abs($0) >= 1.0 ? ($0 > 0.0 ? ~~Math_min(Math_floor($0 / 4294967296.0), 4294967295.0) >>> 0 : ~~Math_ceil(($0 - +(~~$0 >>> 0 >>> 0)) / 4294967296.0) >>> 0) : 0;
+  return ~~$0 >>> 0;
  }
  
  function $11($0) {
diff --git a/test/wasm2js/emscripten.2asm.js b/test/wasm2js/emscripten.2asm.js
index 79da32b8f..664eb654a 100644
--- a/test/wasm2js/emscripten.2asm.js
+++ b/test/wasm2js/emscripten.2asm.js
@@ -80,6 +80,12 @@ function asmFunc(global, env, buffer) {
   return x - -5 | 0 | 0;
  }
  
+ function select(x) {
+  x = x | 0;
+  var wasm2js_i32$0 = 0, wasm2js_i32$1 = 0, wasm2js_i32$2 = 0;
+  return (wasm2js_i32$0 = x, wasm2js_i32$1 = HEAP32[16 >> 2] | 0, wasm2js_i32$2 = x, wasm2js_i32$2 ? wasm2js_i32$0 : wasm2js_i32$1) | 0;
+ }
+ 
  // EMSCRIPTEN_END_FUNCS;
  FUNCTION_TABLE[1] = foo;
  FUNCTION_TABLE[2] = bar;
@@ -89,7 +95,8 @@ function asmFunc(global, env, buffer) {
   "other": other, 
   "__growWasmMemory": __growWasmMemory, 
   "exported": exported, 
-  "sub_zero": sub_zero
+  "sub_zero": sub_zero, 
+  "select": select
  };
 }
 
diff --git a/test/wasm2js/emscripten.2asm.js.opt b/test/wasm2js/emscripten.2asm.js.opt
index ae1c9c53d..4426d7400 100644
--- a/test/wasm2js/emscripten.2asm.js.opt
+++ b/test/wasm2js/emscripten.2asm.js.opt
@@ -41,10 +41,6 @@ function asmFunc(global, env, buffer) {
  }
  
  function bar() {
-  HEAPU8[128 | 0];
-  HEAP8[128 | 0];
-  HEAPU16[128 >> 1];
-  HEAP16[128 >> 1];
   HEAP32[16 >> 2] = 3;
   HEAPF32[16 >> 2] = 7;
   HEAPF64[16 >> 3] = 11;
@@ -66,6 +62,11 @@ function asmFunc(global, env, buffer) {
   return $0 + 5 | 0;
  }
  
+ function select($0) {
+  $0 = $0 | 0;
+  return ($0 ? $0 : HEAP32[16 >> 2]) | 0;
+ }
+ 
  // EMSCRIPTEN_END_FUNCS;
  FUNCTION_TABLE[1] = foo;
  FUNCTION_TABLE[2] = bar;
@@ -75,7 +76,8 @@ function asmFunc(global, env, buffer) {
   "other": other, 
   "__growWasmMemory": __growWasmMemory, 
   "exported": internal, 
-  "sub_zero": sub_zero
+  "sub_zero": sub_zero, 
+  "select": select
  };
 }
 
diff --git a/test/wasm2js/emscripten.wast b/test/wasm2js/emscripten.wast
index 8f797f8fc..5731eacff 100644
--- a/test/wasm2js/emscripten.wast
+++ b/test/wasm2js/emscripten.wast
@@ -13,6 +13,7 @@
  (export "__growWasmMemory" (func $__growWasmMemory))
  (export "exported" (func $exported))
  (export "sub-zero" (func $sub-zero))
+ (export "select" (func $select))
  (func $main
   (drop (call $syscall$6 (i32.const 1) (i32.const 2)))
   (drop (call $syscall$54 (i32.const 3) (i32.const 4)))
@@ -90,5 +91,12 @@
  (func $sub-zero (param $x i32) (result i32)
   (i32.sub (local.get $x) (i32.const -5))
  )
+ (func $select (param $x i32) (result i32)
+  (select
+   (local.get $x)
+   (i32.load (i32.const 16)) ;; we can ignore this implicit trap, no side effects
+   (local.get $x)
+  )
+ )
 )
 
diff --git a/test/wasm2js/float-ops.2asm.js.opt b/test/wasm2js/float-ops.2asm.js.opt
index 4ef79e58a..130fe6bce 100644
--- a/test/wasm2js/float-ops.2asm.js.opt
+++ b/test/wasm2js/float-ops.2asm.js.opt
@@ -247,34 +247,12 @@ function asmFunc(global, env, buffer) {
  
  function $47($0) {
   $0 = Math_fround($0);
-  var $1_1 = 0, $2_1 = 0;
-  $2_1 = ~~$0 >>> 0;
-  if (Math_fround(Math_abs($0)) >= Math_fround(1.0)) {
-   if ($0 > Math_fround(0.0)) {
-    $1_1 = ~~Math_fround(Math_min(Math_fround(Math_floor(Math_fround($0 / Math_fround(4294967296.0)))), Math_fround(4294967296.0))) >>> 0
-   } else {
-    $1_1 = ~~Math_fround(Math_ceil(Math_fround(Math_fround($0 - Math_fround(~~$0 >>> 0 >>> 0)) / Math_fround(4294967296.0)))) >>> 0
-   }
-  } else {
-   $1_1 = 0
-  }
-  return !($2_1 | $1_1) | 0;
+  return !(~~$0 >>> 0 | (Math_fround(Math_abs($0)) >= Math_fround(1.0) ? ($0 > Math_fround(0.0) ? ~~Math_fround(Math_min(Math_fround(Math_floor(Math_fround($0 / Math_fround(4294967296.0)))), Math_fround(4294967296.0))) >>> 0 : ~~Math_fround(Math_ceil(Math_fround(Math_fround($0 - Math_fround(~~$0 >>> 0 >>> 0)) / Math_fround(4294967296.0)))) >>> 0) : 0)) | 0;
  }
  
  function $48($0) {
   $0 = +$0;
-  var $1_1 = 0, $2_1 = 0;
-  $2_1 = ~~$0 >>> 0;
-  if (Math_abs($0) >= 1.0) {
-   if ($0 > 0.0) {
-    $1_1 = ~~Math_min(Math_floor($0 / 4294967296.0), 4294967295.0) >>> 0
-   } else {
-    $1_1 = ~~Math_ceil(($0 - +(~~$0 >>> 0 >>> 0)) / 4294967296.0) >>> 0
-   }
-  } else {
-   $1_1 = 0
-  }
-  return !($2_1 | $1_1) | 0;
+  return !(~~$0 >>> 0 | (Math_abs($0) >= 1.0 ? ($0 > 0.0 ? ~~Math_min(Math_floor($0 / 4294967296.0), 4294967295.0) >>> 0 : ~~Math_ceil(($0 - +(~~$0 >>> 0 >>> 0)) / 4294967296.0) >>> 0) : 0)) | 0;
  }
  
  function legalstub$43($0, $1_1) {