Bug 1598548 part 11 - Remove source note offset for loop backjump. r=arai,tcampbell

For now we still need the source note itself to determine the
stackPhiCount in IonBuilder. Hopefully we can fix that later.

Differential Revision: https://phabricator.services.mozilla.com/D55635

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

js/src/frontend/BytecodeControlStructures.h

@@ -140,11 +140,6 @@ class LoopControl : public BreakableControl {
   BytecodeOffset breakTargetOffset() const { return breakTarget_.offset; }
   BytecodeOffset continueTargetOffset() const { return continueTarget_.offset; }
 
-  // The offset of the backward jump at the loop end from the JSOP_LOOPHEAD.
-  BytecodeOffsetDiff loopEndOffsetFromLoopHead() const {
-    return loopEndOffset_ - head_.offset;
-  }
-
   MOZ_MUST_USE bool emitContinueTarget(BytecodeEmitter* bce);
 
   // Emit a jump to break target from the top level of the loop.

js/src/frontend/BytecodeEmitter.cpp

@@ -5178,11 +5178,7 @@ bool BytecodeEmitter::emitAsyncIterator() {
 bool BytecodeEmitter::emitSpread(bool allowSelfHosted) {
   LoopControl loopInfo(this, StatementKind::Spread);
 
-  // Jump down to the loop condition to minimize overhead assuming at least
-  // one iteration, as the other loop forms do.  Annotate so IonMonkey can
-  // find the loop-closing jump.
-  unsigned noteIndex;
-  if (!newSrcNote(SRC_FOR_OF, &noteIndex)) {
+  if (!newSrcNote(SRC_FOR_OF)) {
     return false;
   }
 
@@ -5243,12 +5239,6 @@ bool BytecodeEmitter::emitSpread(bool allowSelfHosted) {
   // manually.
   bytecodeSection().setStackDepth(bytecodeSection().stackDepth() + 1);
 
-  // Let Ion know where the closing jump of this loop is.
-  if (!setSrcNoteOffset(noteIndex, SrcNote::Loop::BackJumpOffset,
-                        loopInfo.loopEndOffsetFromLoopHead())) {
-    return false;
-  }
-
   // No continues should occur in spreads.
   MOZ_ASSERT(!loopInfo.continues.offset.valid());
 

js/src/frontend/CForEmitter.cpp

@@ -67,7 +67,7 @@ bool CForEmitter::emitCond(const Maybe<uint32_t>& condPos) {
     }
   }
 
-  if (!bce_->newSrcNote(SRC_FOR, &noteIndex_)) {
+  if (!bce_->newSrcNote(SRC_FOR)) {
     return false;
   }
 
@@ -175,14 +175,6 @@ bool CForEmitter::emitEnd(const Maybe<uint32_t>& forPos) {
     return false;
   }
 
-  // The note offset helps us find the loop-closing jump.
-  if (!bce_->setSrcNoteOffset(noteIndex_, SrcNote::Loop::BackJumpOffset,
-                              loopInfo_->loopEndOffsetFromLoopHead()))
-
-  {
-    return false;
-  }
-
   if (!bce_->addTryNote(JSTRY_LOOP, bce_->bytecodeSection().stackDepth(),
                         loopInfo_->headOffset(),
                         loopInfo_->breakTargetOffset())) {

js/src/frontend/CForEmitter.h

@@ -79,9 +79,6 @@ class MOZ_STACK_CLASS CForEmitter {
  private:
   BytecodeEmitter* bce_;
 
-  // The source note index for SRC_FOR.
-  unsigned noteIndex_ = 0;
-
   // Whether the c-style for loop has `cond` and `update`.
   Cond cond_ = Cond::Missing;
   Update update_ = Update::Missing;

js/src/frontend/DoWhileEmitter.cpp

@@ -34,8 +34,7 @@ bool DoWhileEmitter::emitBody(const Maybe<uint32_t>& doPos,
     return false;
   }
 
-  // Emit an annotated nop so IonBuilder can recognize the 'do' loop.
-  if (!bce_->newSrcNote(SRC_DO_WHILE, &noteIndex_)) {
+  if (!bce_->newSrcNote(SRC_DO_WHILE)) {
     return false;
   }
 
@@ -77,12 +76,6 @@ bool DoWhileEmitter::emitEnd() {
     return false;
   }
 
-  // Update the annotation with the back edge position, for IonBuilder.
-  if (!bce_->setSrcNoteOffset(noteIndex_, SrcNote::Loop::BackJumpOffset,
-                              loopInfo_->loopEndOffsetFromLoopHead())) {
-    return false;
-  }
-
   if (!loopInfo_->patchBreaksAndContinues(bce_)) {
     return false;
   }

js/src/frontend/DoWhileEmitter.h

@@ -34,9 +34,6 @@ struct BytecodeEmitter;
 class MOZ_STACK_CLASS DoWhileEmitter {
   BytecodeEmitter* bce_;
 
-  // The source note index for SRC_DO_WHILE.
-  unsigned noteIndex_ = 0;
-
   mozilla::Maybe<LoopControl> loopInfo_;
 
 #ifdef DEBUG

js/src/frontend/ForInEmitter.cpp

@@ -43,8 +43,7 @@ bool ForInEmitter::emitInitialize() {
 
   loopInfo_.emplace(bce_, StatementKind::ForInLoop);
 
-  // Annotate so IonMonkey can find the loop-closing jump.
-  if (!bce_->newSrcNote(SRC_FOR_IN, &noteIndex_)) {
+  if (!bce_->newSrcNote(SRC_FOR_IN)) {
     return false;
   }
 
@@ -144,12 +143,6 @@ bool ForInEmitter::emitEnd(const Maybe<uint32_t>& forPos) {
     return false;
   }
 
-  // Set the srcnote offset so we can find the closing jump.
-  if (!bce_->setSrcNoteOffset(noteIndex_, SrcNote::Loop::BackJumpOffset,
-                              loopInfo_->loopEndOffsetFromLoopHead())) {
-    return false;
-  }
-
   // When we leave the loop body and jump to this point, the iteration value is
   // still on the stack. Account for that by updating the stack depth manually.
   int32_t stackDepth = bce_->bytecodeSection().stackDepth() + 1;

js/src/frontend/ForInEmitter.h

@@ -39,9 +39,6 @@ class EmitterScope;
 class MOZ_STACK_CLASS ForInEmitter {
   BytecodeEmitter* bce_;
 
-  // The source note index for SRC_FOR_IN.
-  unsigned noteIndex_ = 0;
-
 #ifdef DEBUG
   // The stack depth before emitting initialize code inside loop.
   int32_t loopDepth_ = 0;

js/src/frontend/ForOfEmitter.cpp

@@ -70,8 +70,7 @@ bool ForOfEmitter::emitInitialize(const Maybe<uint32_t>& forPos) {
 
   loopInfo_.emplace(bce_, iterDepth, allowSelfHostedIter_, iterKind_);
 
-  // Annotate so IonMonkey can find the loop-closing jump.
-  if (!bce_->newSrcNote(SRC_FOR_OF, &noteIndex_)) {
+  if (!bce_->newSrcNote(SRC_FOR_OF)) {
     return false;
   }
 
@@ -241,12 +240,6 @@ bool ForOfEmitter::emitEnd(const Maybe<uint32_t>& iteratedPos) {
 
   MOZ_ASSERT(bce_->bytecodeSection().stackDepth() == loopDepth_);
 
-  // Let Ion know where the closing jump of this loop is.
-  if (!bce_->setSrcNoteOffset(noteIndex_, SrcNote::Loop::BackJumpOffset,
-                              loopInfo_->loopEndOffsetFromLoopHead())) {
-    return false;
-  }
-
   if (!loopInfo_->patchBreaksAndContinues(bce_)) {
     return false;
   }

js/src/frontend/ForOfEmitter.h

@@ -41,9 +41,6 @@ class EmitterScope;
 class MOZ_STACK_CLASS ForOfEmitter {
   BytecodeEmitter* bce_;
 
-  // The source note index for SRC_FOR_OF.
-  unsigned noteIndex_ = 0;
-
 #ifdef DEBUG
   // The stack depth before emitting IteratorNext code inside loop.
   int32_t loopDepth_ = 0;

js/src/frontend/SourceNotes.h

@@ -38,17 +38,6 @@ namespace js {
 
 class SrcNote {
  public:
-  // SRC_FOR, SRC_DO_WHILE, SRC_WHILE, SRC_FOR_IN, SRC_FOR_OF: Source note for
-  // JSOP_LOOPHEAD at the top of a loop.
-  class Loop {
-   public:
-    enum Fields {
-      // The offset of JSOP_GOTO/JSOP_IFEQ/JSOP_IFNE at the end of the loop from
-      // JSOP_LOOPHEAD.
-      BackJumpOffset,
-      Count,
-    };
-  };
   // SRC_TRY: Source note for JSOP_TRY.
   class Try {
    public:
@@ -83,11 +72,11 @@ class SrcNote {
 // clang-format off
 #define FOR_EACH_SRC_NOTE_TYPE(M)                                                                  \
     M(SRC_NULL,         "null",        0)  /* Terminates a note vector. */                         \
-    M(SRC_FOR,          "for",         SrcNote::Loop::Count) \
-    M(SRC_WHILE,        "while",       SrcNote::Loop::Count) \
-    M(SRC_DO_WHILE,     "do-while",    SrcNote::Loop::Count) \
-    M(SRC_FOR_IN,       "for-in",      SrcNote::Loop::Count) \
-    M(SRC_FOR_OF,       "for-of",      SrcNote::Loop::Count) \
+    M(SRC_FOR,          "for",         0)  /* JSOP_LOOPHEAD is for C-style for-loop. */            \
+    M(SRC_WHILE,        "while",       0)  /* JSOP_LOOPHEAD is for while loop. */                  \
+    M(SRC_DO_WHILE,     "do-while",    0)  /* JSOP_LOOPHEAD is for do-while loop. */               \
+    M(SRC_FOR_IN,       "for-in",      0)  /* JSOP_LOOPHEAD is for for-in loop. */                 \
+    M(SRC_FOR_OF,       "for-of",      0)  /* JSOP_LOOPHEAD is for for-of loop. */                 \
     M(SRC_ASSIGNOP,     "assignop",    0)  /* += or another assign-op follows. */                  \
     M(SRC_CLASS_SPAN,   "class",       2)  /* The starting and ending offsets for the class, used  \
                                               for toString correctness for default ctors. */       \

js/src/frontend/WhileEmitter.cpp

@@ -42,7 +42,7 @@ bool WhileEmitter::emitCond(const Maybe<uint32_t>& whilePos,
 
   loopInfo_.emplace(bce_, StatementKind::WhileLoop);
 
-  if (!bce_->newSrcNote(SRC_WHILE, &noteIndex_)) {
+  if (!bce_->newSrcNote(SRC_WHILE)) {
     return false;
   }
 
@@ -90,11 +90,6 @@ bool WhileEmitter::emitEnd() {
     return false;
   }
 
-  if (!bce_->setSrcNoteOffset(noteIndex_, SrcNote::Loop::BackJumpOffset,
-                              loopInfo_->loopEndOffsetFromLoopHead())) {
-    return false;
-  }
-
   if (!loopInfo_->patchBreaksAndContinues(bce_)) {
     return false;
   }

js/src/frontend/WhileEmitter.h

@@ -37,9 +37,6 @@ struct BytecodeEmitter;
 class MOZ_STACK_CLASS WhileEmitter {
   BytecodeEmitter* bce_;
 
-  // The source note index for SRC_WHILE.
-  unsigned noteIndex_ = 0;
-
   mozilla::Maybe<LoopControl> loopInfo_;
 
   // Cache for the loop body, which is enclosed by the cache in `loopInfo_`,

js/src/shell/js.cpp

@@ -3030,6 +3030,11 @@ static MOZ_MUST_USE bool SrcNotes(JSContext* cx, HandleScript script,
       case SRC_BREAKPOINT:
       case SRC_STEP_SEP:
       case SRC_XDELTA:
+      case SRC_FOR:
+      case SRC_DO_WHILE:
+      case SRC_WHILE:
+      case SRC_FOR_IN:
+      case SRC_FOR_OF:
         break;
 
       case SRC_COLSPAN:
@@ -3051,19 +3056,6 @@ static MOZ_MUST_USE bool SrcNotes(JSContext* cx, HandleScript script,
         ++lineno;
         break;
 
-      case SRC_FOR:
-      case SRC_DO_WHILE:
-      case SRC_WHILE:
-      case SRC_FOR_IN:
-      case SRC_FOR_OF: {
-        unsigned backJumpOffset =
-            GetSrcNoteOffset(sn, SrcNote::Loop::BackJumpOffset);
-        if (!sp->jsprintf(" backjump %u", backJumpOffset)) {
-          return false;
-        }
-        break;
-      }
-
       case SRC_TRY:
         MOZ_ASSERT(JSOp(script->code()[offset]) == JSOP_TRY);
         if (!sp->jsprintf(" offset to jump %u",