Bug 1774390 part 1 - Use separate ExitFrameType for EnsureBareExitFrame. r=iain

This will be used by a later patch, but it's also nice for assertions to use
a different type.

Differential Revision: https://phabricator.services.mozilla.com/D149376

js/src/jit/JSJitFrameIter.cpp

@@ -98,6 +98,13 @@ bool JSJitFrameIter::isBareExit() const {
   return exitFrame()->isBareExit();
 }
 
+bool JSJitFrameIter::isUnwoundJitExit() const {
+  if (type_ != FrameType::Exit) {
+    return false;
+  }
+  return exitFrame()->isUnwoundJitExit();
+}
+
 bool JSJitFrameIter::isFunctionFrame() const {
   return CalleeTokenIsFunction(calleeToken());
 }

js/src/jit/JSJitFrameIter.h

@@ -169,6 +169,7 @@ class JSJitFrameIter {
   bool isBaselineStub() const { return type_ == FrameType::BaselineStub; }
   bool isRectifier() const { return type_ == FrameType::Rectifier; }
   bool isBareExit() const;
+  bool isUnwoundJitExit() const;
   template <typename T>
   bool isExitFrameLayout() const;
 

js/src/jit/JitFrames.cpp

@@ -805,15 +805,14 @@ void HandleException(ResumeFromException* rfe) {
   }
 }
 
-// Turns a JitFrameLayout into an ExitFrameLayout. Note that it has to be a
-// bare exit frame so it's ignored by TraceJitExitFrame.
-void EnsureBareExitFrame(JitActivation* act, JitFrameLayout* frame) {
+// Turns a JitFrameLayout into an UnwoundJit ExitFrameLayout.
+void EnsureUnwoundJitExitFrame(JitActivation* act, JitFrameLayout* frame) {
   ExitFrameLayout* exitFrame = reinterpret_cast<ExitFrameLayout*>(frame);
 
   if (act->jsExitFP() == (uint8_t*)frame) {
     // If we already called this function for the current frame, do
     // nothing.
-    MOZ_ASSERT(exitFrame->isBareExit());
+    MOZ_ASSERT(exitFrame->isUnwoundJitExit());
     return;
   }
 
@@ -830,8 +829,8 @@ void EnsureBareExitFrame(JitActivation* act, JitFrameLayout* frame) {
 #endif
 
   act->setJSExitFP((uint8_t*)frame);
-  exitFrame->footer()->setBareExitFrame();
-  MOZ_ASSERT(exitFrame->isBareExit());
+  exitFrame->footer()->setUnwoundJitExitFrame();
+  MOZ_ASSERT(exitFrame->isUnwoundJitExit());
 }
 
 JSScript* MaybeForwardedScriptFromCalleeToken(CalleeToken token) {
@@ -1225,9 +1224,9 @@ static void TraceJitExitFrame(JSTracer* trc, const JSJitFrameIter& frame) {
     return;
   }
 
-  if (frame.isBareExit()) {
+  if (frame.isBareExit() || frame.isUnwoundJitExit()) {
     // Nothing to trace. Fake exit frame pushed for VM functions with
-    // nothing to trace on the stack.
+    // nothing to trace on the stack or unwound JitFrameLayout.
     return;
   }
 

js/src/jit/JitFrames.h

@@ -175,7 +175,7 @@ static_assert(sizeof(ResumeFromException) % 16 == 0,
 
 void HandleException(ResumeFromException* rfe);
 
-void EnsureBareExitFrame(JitActivation* act, JitFrameLayout* frame);
+void EnsureUnwoundJitExitFrame(JitActivation* act, JitFrameLayout* frame);
 
 void TraceJitActivations(JSContext* cx, JSTracer* trc);
 
@@ -328,6 +328,7 @@ enum class ExitFrameType : uint8_t {
   IonOOLProxy = 0x6,
   WasmGenericJitEntry = 0x7,
   DirectWasmJitCall = 0x8,
+  UnwoundJit = 0xFB,
   InterpreterStub = 0xFC,
   VMFunction = 0xFD,
   LazyLink = 0xFE,
@@ -348,7 +349,9 @@ class ExitFooterFrame {
 
  public:
   static inline size_t Size() { return sizeof(ExitFooterFrame); }
-  void setBareExitFrame() { data_ = uintptr_t(ExitFrameType::Bare); }
+  void setUnwoundJitExitFrame() {
+    data_ = uintptr_t(ExitFrameType::UnwoundJit);
+  }
   ExitFrameType type() const {
     static_assert(sizeof(ExitFrameType) == sizeof(uint8_t),
                   "Code assumes ExitFrameType fits in a byte");
@@ -422,6 +425,9 @@ class ExitFrameLayout : public CommonFrameLayout {
     return footer()->type() == ExitFrameType::VMFunction;
   }
   inline bool isBareExit() { return footer()->type() == ExitFrameType::Bare; }
+  inline bool isUnwoundJitExit() {
+    return footer()->type() == ExitFrameType::UnwoundJit;
+  }
 
   // See the various exit frame layouts below.
   template <typename T>

js/src/jit/VMFunctions.cpp

@@ -1027,7 +1027,7 @@ bool DebugEpilogue(JSContext* cx, BaselineFrame* frame, const jsbytecode* pc,
     // Pop this frame by updating packedExitFP, so that the exception
     // handling code will start at the previous frame.
     JitFrameLayout* prefix = frame->framePrefix();
-    EnsureBareExitFrame(cx->activation()->asJit(), prefix);
+    EnsureUnwoundJitExitFrame(cx->activation()->asJit(), prefix);
     return false;
   }
 

js/src/vm/FrameIter.cpp

@@ -14,7 +14,7 @@
 #include <stdlib.h>  // getenv
 
 #include "jit/BaselineFrame.h"   // js::jit::BaselineFrame
-#include "jit/JitFrames.h"       // js::jit::EnsureBareExitFrame
+#include "jit/JitFrames.h"       // js::jit::EnsureUnwoundJitExitFrame
 #include "jit/JSJitFrameIter.h"  // js::jit::{FrameType,InlineFrameIterator,JSJitFrameIter,MaybeReadFallback,SnapshotIterator}
 #include "js/GCAPI.h"            // JS::AutoSuppressGCAnalysis
 #include "js/Principals.h"       // JSSubsumesOp
@@ -227,7 +227,7 @@ void JitFrameIter::operator++() {
       // don't see this frame when they use ScriptFrameIter, and (2)
       // ScriptFrameIter does not crash when accessing an IonScript
       // that's destroyed by the ionScript->decref call.
-      EnsureBareExitFrame(act_, prevFrame);
+      EnsureUnwoundJitExitFrame(act_, prevFrame);
     }
   } else if (isWasm()) {
     ++asWasm();