Bug 1608509 - Part 1: Fix a few odd comments. r=jandem.

The comment about JSOP_GLOBALTHIS and JSOP_FUNCTIONTHIS may never have been
sensible; JSOP_FUNCTIONTHIS never walks the environment chain, as it is used
only in non-arrow functions, which take `this` as an argument in the CallArgs.

JSOP_LOOPENTRY and JSOP_TRACE are gone. So is JSOP_SPREAD.

"JSOP_POPs" was eccentric in a way that would be unclear with CamelCase.

Differential Revision: https://phabricator.services.mozilla.com/D59799

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

js/src/builtin/Eval.cpp

@@ -571,9 +571,7 @@ JS_FRIEND_API bool js::ExecuteInJSMEnvironment(JSContext* cx,
     //      WithEnvironmentObject[target=targetObj]
     //      LexicalEnvironmentObject[this=targetObj] (*)
     //
-    //  (*) This environment intentionally intercepts JSOP_GLOBALTHIS, but
-    //  not JSOP_FUNCTIONTHIS (which instead will fallback to the NSVO). I
-    //  don't make the rules, I just record them.
+    //  (*) This environment intercepts JSOP_GLOBALTHIS.
 
     // Wrap the target objects in WithEnvironments.
     if (!js::CreateObjectsForEnvironmentChain(cx, targetObj, env, &env)) {

js/src/frontend/BytecodeEmitter.cpp

@@ -489,7 +489,7 @@ bool BytecodeEmitter::emitPopN(unsigned n) {
     return emit1(JSOP_POP);
   }
 
-  // 2 JSOP_POPs (2 bytes) are shorter than JSOP_POPN (3 bytes).
+  // 2 JSOP_POP instructions (2 bytes) are shorter than JSOP_POPN (3 bytes).
   if (n == 2) {
     return emit1(JSOP_POP) && emit1(JSOP_POP);
   }
@@ -593,9 +593,9 @@ Maybe<uint32_t> BytecodeEmitter::getOffsetForLoop(ParseNode* nextpn) {
     return Nothing();
   }
 
-  // Try to give the JSOP_LOOPHEAD and JSOP_LOOPENTRY the same line number as
-  // the next instruction. nextpn is often a block, in which case the next
-  // instruction typically comes from the first statement inside.
+  // Try to give the JSOP_LOOPHEAD the same line number as the next
+  // instruction. nextpn is often a block, in which case the next instruction
+  // typically comes from the first statement inside.
   if (nextpn->is<LexicalScopeNode>()) {
     nextpn = nextpn->as<LexicalScopeNode>().scopeBody();
   }

js/src/jit/BaselineCodeGen.cpp

@@ -1777,7 +1777,7 @@ bool BaselineCodeGen<Handler>::emit_JSOP_DUP() {
   frame.popRegsAndSync(1);
   masm.moveValue(R0, R1);
 
-  // inc/dec ops use DUP followed by ONE, ADD. Push R0 last to avoid a move.
+  // inc/dec ops use DUP followed by INC/DEC. Push R0 last to avoid a move.
   frame.push(R1);
   frame.push(R0);
   return true;

js/src/jit/BaselineCodeGen.h

@@ -297,7 +297,7 @@ class BaselineCompilerHandler {
   FixedList<Label> labels_;
   RetAddrEntryVector retAddrEntries_;
 
-  // Native code offsets for OSR at JSOP_LOOPENTRY ops.
+  // Native code offsets for OSR at JSOP_LOOPHEAD ops.
   using OSREntryVector =
       Vector<BaselineScript::OSREntry, 16, SystemAllocPolicy>;
   OSREntryVector osrEntries_;

js/src/jit/BaselineJIT.h

@@ -215,7 +215,7 @@ struct BaselineScript final {
   };
 
   // Native code offset for OSR from Baseline Interpreter into Baseline JIT at
-  // JSOP_LOOPENTRY ops.
+  // JSOP_LOOPHEAD ops.
   class OSREntry : public BasePCToNativeEntry {
    public:
     using BasePCToNativeEntry::BasePCToNativeEntry;

js/src/jit/MIR.h

@@ -1322,7 +1322,7 @@ class MStart : public MNullaryInstruction {
 };
 
 // Instruction marking on entrypoint for on-stack replacement.
-// OSR may occur at loop headers (at JSOP_TRACE).
+// OSR may occur at loop headers (at JSOP_LOOPHEAD).
 // There is at most one MOsrEntry per MIRGraph.
 class MOsrEntry : public MNullaryInstruction {
  protected:

js/src/vm/Interpreter-inl.h

@@ -642,13 +642,13 @@ static MOZ_ALWAYS_INLINE bool InitArrayElemOperation(JSContext* cx,
    * If val is a hole, do not call DefineElement.
    *
    * Furthermore, if the current op is JSOP_INITELEM_INC, always call
-   * SetLengthProperty even if it is not the last element initialiser,
-   * because it may be followed by JSOP_SPREAD, which will not set the array
+   * SetLengthProperty even if it is not the last element initialiser, because
+   * it may be followed by a SpreadElement loop, which will not set the array
    * length if nothing is spread.
    *
    * Alternatively, if the current op is JSOP_INITELEM_ARRAY, the length will
    * have already been set by the earlier JSOP_NEWARRAY; JSOP_INITELEM_ARRAY
-   * cannot follow JSOP_SPREAD.
+   * cannot follow SpreadElements.
    */
   if (val.isMagic(JS_ELEMENTS_HOLE)) {
     if (op == JSOP_INITELEM_INC) {