Bug 1584758 - Use BytecodeLocation and BytecodeIterator in IonBuilder::analyzeNewLoopTypes. r=mgaudet

Replaced uses of `jsbytecode*` and `pcToOffset` in `IonBuilder::analyzeNewLoopTypes` with bytecode abstraction classes
`BytecodeLocation` and `BytecodeIterator`.

Differential Revision: https://phabricator.services.mozilla.com/D47855

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

js/src/jit/IonBuilder.cpp

@@ -22,6 +22,8 @@
 #include "jit/Lowering.h"
 #include "jit/MIRGraph.h"
 #include "vm/ArgumentsObject.h"
+#include "vm/BytecodeIterator.h"
+#include "vm/BytecodeLocation.h"
 #include "vm/BytecodeUtil.h"
 #include "vm/EnvironmentObject.h"
 #include "vm/Instrumentation.h"
@@ -33,6 +35,8 @@
 #include "gc/Nursery-inl.h"
 #include "jit/CompileInfo-inl.h"
 #include "jit/shared/Lowering-shared-inl.h"
+#include "vm/BytecodeIterator-inl.h"
+#include "vm/BytecodeLocation-inl.h"
 #include "vm/BytecodeUtil-inl.h"
 #include "vm/EnvironmentObject-inl.h"
 #include "vm/JSScript-inl.h"
@@ -626,49 +630,54 @@ AbortReasonOr<Ok> IonBuilder::analyzeNewLoopTypes(
     }
   }
 
-  // Get the start and end pc of this loop.
-  jsbytecode* start = loopEntryBlock->stopPc();
-  start += GetBytecodeLength(start);
-  jsbytecode* end = loopEntry->loopStopPc();
+  // Get the start and end bytecode locations of this loop.
+  BytecodeLocation start(script_, loopEntryBlock->stopPc());
+  start = start.next();
+  BytecodeLocation end(script_, loopEntry->loopStopPc());
 
   // Iterate the bytecode quickly to seed possible types in the loopheader.
-  jsbytecode* last = nullptr;
-  jsbytecode* earlier = nullptr;
-  for (jsbytecode* pc = start; pc != end;
-       earlier = last, last = pc, pc += GetBytecodeLength(pc)) {
+  BytecodeLocation last = start;
+  BytecodeLocation earlier = last;
+
+  for (auto it : BytecodeLocationRange(start, end)) {
+    // Keeping track of previous BytecodeLocation values
+    earlier = last;
+    last = it;
+
     uint32_t slot;
-    if (*pc == JSOP_SETLOCAL) {
-      slot = info().localSlot(GET_LOCALNO(pc));
-    } else if (*pc == JSOP_SETARG) {
-      slot = info().argSlotUnchecked(GET_ARGNO(pc));
+
+    if (it.is(JSOP_SETLOCAL)) {
+      slot = info().localSlot(it.local());
+    } else if (it.is(JSOP_SETARG)) {
+      slot = info().argSlotUnchecked(it.arg());
     } else {
       continue;
     }
     if (slot >= info().firstStackSlot()) {
       continue;
     }
-    if (!last) {
+    if (!last.isValid(script_)) {
       continue;
     }
 
     MPhi* phi = entry->getSlot(slot)->toPhi();
 
-    if (*last == JSOP_POS || *last == JSOP_TONUMERIC) {
+    if (last.is(JSOP_POS) || last.is(JSOP_TONUMERIC)) {
       last = earlier;
     }
 
-    if (BytecodeOpHasTypeSet(JSOp(*last))) {
-      TemporaryTypeSet* typeSet = bytecodeTypes(last);
+    if (last.opHasTypeSet()) {
+      TemporaryTypeSet* typeSet = bytecodeTypes(last.toRawBytecode());
       if (!typeSet->empty()) {
         MIRType type = typeSet->getKnownMIRType();
         if (!phi->addBackedgeType(alloc(), type, typeSet)) {
           return abort(AbortReason::Alloc);
         }
       }
-    } else if (*last == JSOP_GETLOCAL || *last == JSOP_GETARG) {
-      uint32_t slot = (*last == JSOP_GETLOCAL)
-                          ? info().localSlot(GET_LOCALNO(last))
-                          : info().argSlotUnchecked(GET_ARGNO(last));
+    } else if (last.is(JSOP_GETLOCAL) || last.is(JSOP_GETARG)) {
+      uint32_t slot = (last.is(JSOP_GETLOCAL))
+                          ? info().localSlot(last.local())
+                          : info().argSlotUnchecked(last.arg());
       if (slot < info().firstStackSlot()) {
         MPhi* otherPhi = entry->getSlot(slot)->toPhi();
         if (otherPhi->hasBackedgeType()) {
@@ -680,7 +689,7 @@ AbortReasonOr<Ok> IonBuilder::analyzeNewLoopTypes(
       }
     } else {
       MIRType type = MIRType::None;
-      switch (*last) {
+      switch (last.getOp()) {
         case JSOP_VOID:
         case JSOP_UNDEFINED:
           type = MIRType::Undefined;
@@ -746,7 +755,7 @@ AbortReasonOr<Ok> IonBuilder::analyzeNewLoopTypes(
         case JSOP_NEG:
         case JSOP_INC:
         case JSOP_DEC:
-          type = inspector->expectedResultType(last);
+          type = inspector->expectedResultType(last.toRawBytecode());
           break;
         case JSOP_BIGINT:
           type = MIRType::BigInt;

js/src/vm/BytecodeIterator-inl.h

@@ -10,6 +10,7 @@
 #include "vm/BytecodeIterator.h"
 
 #include "vm/JSScript.h"
+
 namespace js {
 
 inline BytecodeIterator::BytecodeIterator(const JSScript* script)

js/src/vm/BytecodeLocation.h

@@ -35,7 +35,6 @@ class BytecodeLocation {
 #ifdef DEBUG
   const JSScript* debugOnlyScript_;
 #endif
-
   // Construct a new BytecodeLocation, while borrowing scriptIdentity
   // from some other BytecodeLocation.
   BytecodeLocation(const BytecodeLocation& loc, RawBytecode pc)
@@ -49,6 +48,9 @@ class BytecodeLocation {
   }
 
  public:
+  // Disallow the creation of an uninitialized location.
+  BytecodeLocation() = delete;
+
   BytecodeLocation(const JSScript* script, RawBytecode pc)
       : rawBytecode_(pc)
 #ifdef DEBUG
@@ -132,6 +134,10 @@ class BytecodeLocation {
 
   uint32_t icIndex() const { return GET_ICINDEX(rawBytecode_); }
 
+  uint32_t local() const { return GET_LOCALNO(rawBytecode_); }
+
+  uint16_t arg() const { return GET_ARGNO(rawBytecode_); }
+
   bool isEqualityOp() const { return IsEqualityOp(getOp()); }
 
   bool isStrictEqualityOp() const {