fix else fusing when label has multiple assigns or checks

3 files changed, 164 insertions, 15 deletions

diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index c38b51d5..1c3bc8c0 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -879,6 +879,41 @@ function simplifyIfs(ast) {
 
     if (simplifiedAnElse) {
       // there may be fusing opportunities
+
+      // we can only fuse if we remove all uses of the label. if there are
+      // other ones - if the label check can be reached from elsewhere -
+      // we must leave it
+      var abort = false;
+
+      var labelAssigns = {};
+      traverse(func, function(node, type) {
+        if (type === 'assign' && node[2][0] === 'name' && node[2][1] === 'label') {
+          if (node[3][0] === 'num') {
+            var value = node[3][1];
+            labelAssigns[value] = (labelAssigns[value] || 0) + 1;
+          } else {
+            // label is assigned a dynamic value (like from indirectbr), we cannot do anything
+            abort = true;
+          }
+        }
+      });
+      if (abort) return;
+
+      var labelChecks = {};
+      traverse(func, function(node, type) {
+        if (type === 'binary' && node[1] === '==' && node[2][0] === 'binary' && node[2][1] === '|' &&
+            node[2][2][0] === 'name' && node[2][2][1] === 'label') {
+          if (node[3][0] === 'num') {
+            var value = node[3][1];
+            labelChecks[value] = (labelChecks[value] || 0) + 1;
+          } else {
+            // label is checked vs a dynamic value (like from indirectbr), we cannot do anything
+            abort = true;
+          }
+        }
+      });
+      if (abort) return;
+
       traverse(func, function(node, type) {
         var stats = getStatements(node);
         if (stats) {
@@ -894,7 +929,7 @@ function simplifyIfs(ast) {
                   postCond[3][0] === 'num') {
                 var postValue = postCond[3][1];
                 var preElse = pre[3];
-                if (preElse[0] === 'block' && preElse[1] && preElse[1].length === 1) {
+                if (labelAssigns[postValue] === 1 && labelChecks[postValue] === 1 && preElse[0] === 'block' && preElse[1] && preElse[1].length === 1) {
                   var preStat = preElse[1][0];
                   if (preStat[0] === 'stat' && preStat[1][0] === 'assign' &&
                       preStat[1][1] === true && preStat[1][2][0] === 'name' && preStat[1][2][1] === 'label' &&
diff --git a/tools/test-js-optimizer-si-output.js b/tools/test-js-optimizer-si-output.js
index a6e8f53e..0a2468b5 100644
--- a/tools/test-js-optimizer-si-output.js
+++ b/tools/test-js-optimizer-si-output.js
@@ -112,18 +112,27 @@ function a() {
  if (x ? y : 0) {
   f();
  } else {
-  label = 5;
+  label = 52;
  }
- if ((label | 0) == 6) {
+ if ((label | 0) == 62) {
   label = 0;
   a();
  }
  if (x ? y : 0) {
   f();
  } else {
-  label = 5;
+  label = 53;
  }
- if ((label | 0) == 5) {
+ if ((label | 0) == 53) {
+  a();
+ }
+ if (x ? y : 0) {
+  label = 54;
+ } else {
+  label = 54;
+ }
+ if ((label | 0) == 54) {
+  label = 0;
   a();
  }
 }
@@ -138,4 +147,44 @@ function b() {
   a();
  }
 }
+function c() {
+ label = x;
+ if (x ? y : 0) {
+  f();
+ } else {
+  label = 151;
+ }
+ if ((label | 0) == 151) {
+  label = 0;
+  a();
+ }
+}
+function d() {
+ if (x ? y : 0) {
+  f();
+ } else {
+  label = 251;
+ }
+ if ((label | 0) == 251) {
+  label = 0;
+  a();
+ }
+ if ((label | 0) == 251) {
+  a();
+ }
+}
+function e() {
+ if (x ? y : 0) {
+  f();
+ } else {
+  label = 351;
+ }
+ if ((label | 0) == 351) {
+  label = 0;
+  a();
+ }
+ if ((label | 0) == x) {
+  a();
+ }
+}
 
diff --git a/tools/test-js-optimizer-si.js b/tools/test-js-optimizer-si.js
index 78683d6c..9bb82da4 100644
--- a/tools/test-js-optimizer-si.js
+++ b/tools/test-js-optimizer-si.js
@@ -130,12 +130,12 @@ function a() {
     if (y) {
       f();
     } else {
-      label = 5;
+      label = 51;
     }
   } else {
-    label = 5;
+    label = 51;
   }
-  if ((label|0) == 5) {
+  if ((label|0) == 51) {
     label = 0;
     a();
   }
@@ -143,12 +143,12 @@ function a() {
     if (y) {
       f();
     } else {
-      label = 5;
+      label = 52;
     }
   } else {
-    label = 5;
+    label = 52;
   }
-  if ((label|0) == 6) {
+  if ((label|0) == 62) {
     label = 0;
     a();
   }
@@ -156,12 +156,25 @@ function a() {
     if (y) {
       f();
     } else {
-      label = 5;
+      label = 53;
     }
   } else {
-    label = 5;
+    label = 53;
   }
-  if ((label|0) == 5) {
+  if ((label|0) == 53) {
+    a();
+  }
+  if (x) {
+    if (y) {
+      label = 54; // extra label setting, cannot fuse here
+    } else {
+      label = 54;
+    }
+  } else {
+    label = 54;
+  }
+  if ((label|0) == 54) {
+    label = 0;
     a();
   }
 }
@@ -176,4 +189,56 @@ function b() {
     a();
   }
 }
-// EMSCRIPTEN_GENERATED_FUNCTIONS: ["a", "b"]
+function c() {
+  label = x; // dynamic assign to label, suppresses label removal
+  if (x) {
+    if (y) {
+      f();
+    } else {
+      label = 151;
+    }
+  } else {
+    label = 151;
+  }
+  if ((label|0) == 151) {
+    label = 0;
+    a();
+  }
+}
+function d() {
+  if (x) {
+    if (y) {
+      f();
+    } else {
+      label = 251;
+    }
+  } else {
+    label = 251;
+  }
+  if ((label|0) == 251) {
+    label = 0;
+    a();
+  }
+  if ((label|0) == 251) { // extra check of label, suppresses label removal
+    a();
+  }
+}
+function e() {
+  if (x) {
+    if (y) {
+      f();
+    } else {
+      label = 351;
+    }
+  } else {
+    label = 351;
+  }
+  if ((label|0) == 351) {
+    label = 0;
+    a();
+  }
+  if ((label|0) == x) { // dynamic check of label, suppresses label removal
+    a();
+  }
+}
+// EMSCRIPTEN_GENERATED_FUNCTIONS: ["a", "b", "c", "d"]