Bug 1919246 - Back out D221953 and add tests. r=mgaudet

For now back out D221953 because it was an optional change to improve codegen a bit
for loops that contain an OSR loop, but it's probably not worth the complexity to
try to handle this.

Differential Revision: https://phabricator.services.mozilla.com/D222486

js/src/jit-test/tests/ion/bug1919246-1.js

@@ -0,0 +1,13 @@
+// |jit-test| --fast-warmup
+function test() {
+  var c = [1];
+  for (var d in c) {
+    for (var i = 0; i < 30; i++) {
+      try {
+        a.push(g);
+      } catch (e) { }
+      for (var j = 0; j < 30; j++) { }
+    }
+  }
+}
+test();

js/src/jit-test/tests/ion/bug1919246-2.js

@@ -0,0 +1,12 @@
+// |jit-test| --fast-warmup
+function f() {
+  var i = 0;
+  while (true) {
+    for (let a = 2; a;) {
+      for (c = 0; c < 10;) {
+        if (i++ > 2500) return;
+      }
+    }
+  }
+}
+f();

js/src/jit/IonAnalysis.cpp

@@ -5081,6 +5081,13 @@ bool jit::MakeLoopsContiguous(MIRGraph& graph) {
       continue;
     }
 
+    // If there's an OSR block entering the loop in the middle, it's tricky,
+    // so don't try to handle it, for now.
+    if (canOsr) {
+      UnmarkLoopBlocks(graph, header);
+      continue;
+    }
+
     // Move all blocks between header and backedge that aren't marked to
     // the end of the loop, making the loop itself contiguous.
     MakeLoopContiguous(graph, header, numMarked);