Bug 1598548 part 12 - Don't treat JSOP_IFEQ as a backedge. r=arai

Now all loops use either JSOP_IFNE (do-while) or JSOP_GOTO (other loops).

Differential Revision: https://phabricator.services.mozilla.com/D55723

--HG--
extra : moz-landing-system : lando

js/src/frontend/BytecodeControlStructures.h

@@ -102,7 +102,7 @@ class LoopControl : public BreakableControl {
   //     {loop update if present}
   //
   //     # Loop end, backward jump
-  //     JSOP_GOTO/JSOP_IFEQ/JSOP_IFNE head
+  //     JSOP_GOTO/JSOP_IFNE head
   //
   //   breakTarget:
 

js/src/jit/IonBuilder.cpp

@@ -3112,7 +3112,7 @@ AbortReasonOr<Ok> IonBuilder::jsop_dup2() {
 }
 
 AbortReasonOr<Ok> IonBuilder::visitTestBackedge(JSOp op, bool* restarted) {
-  MOZ_ASSERT(op == JSOP_IFNE || op == JSOP_IFEQ);
+  MOZ_ASSERT(op == JSOP_IFNE);
   MOZ_ASSERT(loopDepth_ > 0);
 
   MDefinition* ins = current->pop();
@@ -3128,15 +3128,8 @@ AbortReasonOr<Ok> IonBuilder::visitTestBackedge(JSOp op, bool* restarted) {
   MBasicBlock* backedge;
   MOZ_TRY_VAR(backedge, newBlock(current, loopHead));
 
-  if (op == JSOP_IFNE) {
-    current->end(newTest(ins, backedge, nullptr));
-    MOZ_TRY(
-        addPendingEdge(PendingEdge::NewTestFalse(current, op), successorPC));
-  } else {
-    MOZ_ASSERT(op == JSOP_IFEQ);
-    current->end(newTest(ins, nullptr, backedge));
-    MOZ_TRY(addPendingEdge(PendingEdge::NewTestTrue(current, op), successorPC));
-  }
+  current->end(newTest(ins, backedge, nullptr));
+  MOZ_TRY(addPendingEdge(PendingEdge::NewTestFalse(current, op), successorPC));
 
   MOZ_TRY(startTraversingBlock(backedge));
   return visitBackEdge(restarted);

js/src/vm/BytecodeUtil.h

@@ -274,7 +274,6 @@ static inline bool IsBackedgePC(jsbytecode* pc) {
   switch (JSOp(*pc)) {
     case JSOP_GOTO:
     case JSOP_IFNE:
-    case JSOP_IFEQ:
       return GET_JUMP_OFFSET(pc) < 0;
     default:
       return false;