Fix test262 failures related to <, <=, in and instanceof

Fixed-by: @kzc

README.md

@@ -291,12 +291,19 @@ to set `true`; it's effectively a shortcut for `foo=true`).
 
 - `unsafe` (default: false) -- apply "unsafe" transformations (discussion below)
 
+- `unsafe_comps` (default: false) -- Reverse `<` and `<=` to `>` and `>=` to
+  allow improved compression. This might be unsafe when an at least one of two
+  operands is an object with computed values due the use of methods like `get`,
+  or `valueOf`. This could cause change in execution order after operands in the
+  comparison are switching. Compression only works if both `comparisons` and
+  `unsafe_comps` are both set to true.
+
 - `conditionals` -- apply optimizations for `if`-s and conditional
   expressions
 
 - `comparisons` -- apply certain optimizations to binary nodes, for example:
-  `!(a <= b) → a > b` (only when `unsafe`), attempts to negate binary nodes,
-  e.g. `a = !b && !c && !d && !e → a=!(b||c||d||e)` etc.
+  `!(a <= b) → a > b` (only when `unsafe_comps`), attempts to negate binary
+  nodes, e.g. `a = !b && !c && !d && !e → a=!(b||c||d||e)` etc.
 
 - `evaluate` -- attempt to evaluate constant expressions
 
@@ -415,7 +422,7 @@ them. If you are targeting < ES6 environments, use `/** @const */ var`.
 <a name="codegen-options"></a>
 
 #### Conditional compilation, API
-You can also use conditional compilation via the programmatic API. With the difference that the 
+You can also use conditional compilation via the programmatic API. With the difference that the
 property name is `global_defs` and is a compressor property:
 
 ```js

lib/compress.js

@@ -1079,8 +1079,6 @@ merge(Compressor.prototype, {
               case "<="         : return ev(left, c) <=         ev(right, c);
               case ">"          : return ev(left, c) >          ev(right, c);
               case ">="         : return ev(left, c) >=         ev(right, c);
-              case "in"         : return ev(left, c) in         ev(right, c);
-              case "instanceof" : return ev(left, c) instanceof ev(right, c);
             }
             throw def;
         });
@@ -2502,9 +2500,11 @@ merge(Compressor.prototype, {
                 });
                 self = best_of(self, negated);
             }
-            switch (self.operator) {
-              case "<": reverse(">"); break;
-              case "<=": reverse(">="); break;
+            if (compressor.option("unsafe_comps")) {
+                switch (self.operator) {
+                  case "<": reverse(">"); break;
+                  case "<=": reverse(">="); break;
+                }
             }
         }
         if (self.operator == "+" && self.right instanceof AST_String

test/compress/asm.js

@@ -92,7 +92,7 @@ asm_mixed: {
             function logSum(start, end) {
                 start = 0 | start, end = 0 | end;
                 var sum = 0, p = 0, q = 0;
-                for (p = start << 3, q = end << 3; (0 | q) > (0 | p); p = p + 8 | 0) sum += +log(values[p >> 3]);
+                for (p = start << 3, q = end << 3; (0 | p) < (0 | q); p = p + 8 | 0) sum += +log(values[p >> 3]);
                 return +sum;
             }
             function geometricMean(start, end) {

test/compress/comparing.js

@@ -0,0 +1,76 @@
+keep_comparisons: {
+    options = {
+        comparisons: true,
+        unsafe_comps: false
+    }
+    input: {
+        var obj1 = {
+            valueOf: function() {triggeredFirst();}
+        }
+        var obj2 = {
+            valueOf: function() {triggeredSecond();}
+        }
+        var result1 = obj1 <= obj2;
+        var result2 = obj1 <  obj2;
+        var result3 = obj1 >= obj2;
+        var result4 = obj1 >  obj2;
+    }
+    expect: {
+        var obj1 = {
+            valueOf: function() {triggeredFirst();}
+        }
+        var obj2 = {
+            valueOf: function() {triggeredSecond();}
+        }
+        var result1 = obj1 <= obj2;
+        var result2 = obj1 <  obj2;
+        var result3 = obj1 >= obj2;
+        var result4 = obj1 >  obj2;
+    }
+}
+
+keep_comparisons_with_unsafe_comps: {
+    options = {
+        comparisons: true,
+        unsafe_comps: true
+    }
+    input: {
+        var obj1 = {
+            valueOf: function() {triggeredFirst();}
+        }
+        var obj2 = {
+            valueOf: function() {triggeredSecond();}
+        }
+        var result1 = obj1 <= obj2;
+        var result2 = obj1 <  obj2;
+        var result3 = obj1 >= obj2;
+        var result4 = obj1 >  obj2;
+    }
+    expect: {
+        var obj1 = {
+            valueOf: function() {triggeredFirst();}
+        }
+        var obj2 = {
+            valueOf: function() {triggeredSecond();}
+        }
+        var result1 = obj2 >= obj1;
+        var result2 = obj2 >  obj1;
+        var result3 = obj1 >= obj2;
+        var result4 = obj1 >  obj2;
+    }
+}
+
+dont_change_in_or_instanceof_expressions: {
+    input: {
+        1 in 1;
+        null in null;
+        1 instanceof 1;
+        null instanceof null;
+    }
+    expect: {
+        1 in 1;
+        null in null;
+        1 instanceof 1;
+        null instanceof null;
+    }
+}