Bug 1428453 - Baldr: remove WasmFrameIter::debugTrapCallsite() (r=yury)

MozReview-Commit-ID: AHjWPINanvF

js/src/wasm/WasmBuiltins.cpp

@@ -96,17 +96,24 @@ static bool
 WasmHandleDebugTrap()
 {
     JitActivation* activation = CallingActivation();
-    MOZ_ASSERT(activation);
     JSContext* cx = activation->cx();
+    Frame* fp = activation->wasmExitFP();
+    Instance* instance = fp->tls->instance;
+    const Code& code = instance->code();
+    MOZ_ASSERT(code.metadata().debugEnabled);
 
-    WasmFrameIter frame(activation);
-    MOZ_ASSERT(frame.debugEnabled());
-    const CallSite* site = frame.debugTrapCallsite();
+    // The debug trap stub is the innermost frame. It's return address is the
+    // actual trap site.
+    const CallSite* site = code.lookupCallSite(fp->returnAddress);
     MOZ_ASSERT(site);
+
+    // Advance to the actual trapping frame.
+    fp = fp->callerFP;
+    DebugFrame* debugFrame = DebugFrame::from(fp);
+
     if (site->kind() == CallSite::EnterFrame) {
-        if (!frame.instance()->enterFrameTrapsEnabled())
+        if (!instance->enterFrameTrapsEnabled())
             return true;
-        DebugFrame* debugFrame = frame.debugFrame();
         debugFrame->setIsDebuggee();
         debugFrame->observe(cx);
         // TODO call onEnterFrame
@@ -121,15 +128,13 @@ WasmHandleDebugTrap()
         return status == JSTRAP_CONTINUE;
     }
     if (site->kind() == CallSite::LeaveFrame) {
-        DebugFrame* debugFrame = frame.debugFrame();
         debugFrame->updateReturnJSValue();
         bool ok = Debugger::onLeaveFrame(cx, debugFrame, nullptr, true);
         debugFrame->leave(cx);
         return ok;
     }
 
-    DebugFrame* debugFrame = frame.debugFrame();
-    DebugState& debug = frame.instance()->debug();
+    DebugState& debug = instance->debug();
     MOZ_ASSERT(debug.hasBreakpointTrapAtOffset(site->lineOrBytecode()));
     if (debug.stepModeEnabled(debugFrame->funcIndex())) {
         RootedValue result(cx, UndefinedValue());

js/src/wasm/WasmFrameIter.cpp

@@ -216,20 +216,7 @@ DebugFrame*
 WasmFrameIter::debugFrame() const
 {
     MOZ_ASSERT(!done());
-    MOZ_ASSERT(debugEnabled());
-    return reinterpret_cast<DebugFrame*>((uint8_t*)fp_ - DebugFrame::offsetOfFrame());
-}
-
-const CallSite*
-WasmFrameIter::debugTrapCallsite() const
-{
-    MOZ_ASSERT(!done());
-    MOZ_ASSERT(callsite_);
-    MOZ_ASSERT(debugEnabled());
-    MOZ_ASSERT(callsite_->kind() == CallSite::EnterFrame ||
-               callsite_->kind() == CallSite::LeaveFrame ||
-               callsite_->kind() == CallSite::Breakpoint);
-    return callsite_;
+    return DebugFrame::from(fp_);
 }
 
 /*****************************************************************************/

js/src/wasm/WasmFrameIter.h

@@ -91,7 +91,6 @@ class WasmFrameIter
     void** unwoundAddressOfReturnAddress() const;
     bool debugEnabled() const;
     DebugFrame* debugFrame() const;
-    const CallSite* debugTrapCallsite() const;
 };
 
 enum class SymbolicAddress;

js/src/wasm/WasmTypes.cpp

@@ -562,6 +562,15 @@ wasm::ComputeMappedSize(uint32_t maxSize)
 
 #endif  // WASM_HUGE_MEMORY
 
+/* static */ DebugFrame*
+DebugFrame::from(Frame* fp)
+{
+    MOZ_ASSERT(fp->tls->instance->code().metadata().debugEnabled);
+    auto* df = reinterpret_cast<DebugFrame*>((uint8_t*)fp - DebugFrame::offsetOfFrame());
+    MOZ_ASSERT(fp->instance() == df->instance());
+    return df;
+}
+
 void
 DebugFrame::alignmentStaticAsserts()
 {

js/src/wasm/WasmTypes.h

@@ -1879,6 +1879,7 @@ class DebugFrame
     Frame frame_;
 
   public:
+    static DebugFrame* from(Frame* fp);
     Frame& frame() { return frame_; }
     uint32_t funcIndex() const { return funcIndex_; }
     Instance* instance() const { return frame_.instance(); }