[compiler] Don't fallthrough liveness across Return/Throw

Return/Throw/Rethrow all unconditionally exit the bytecode, so the
bytecode liveness analysis shouldn't merge their next bytecode's
liveness into them.

Change-Id: I62f53d16f2763e12a702b8b40b2573c264488968
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3439915
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78951}

src/compiler/bytecode-analysis.cc

@@ -254,7 +254,9 @@ void UpdateOutLiveness(Bytecode bytecode, BytecodeLiveness& liveness,
   // Update from next bytecode (unless there isn't one or this is an
   // unconditional jump).
   if (next_bytecode_in_liveness != nullptr &&
-      !Bytecodes::IsUnconditionalJump(bytecode)) {
+      !Bytecodes::IsUnconditionalJump(bytecode) &&
+      !Bytecodes::Returns(bytecode) &&
+      !Bytecodes::UnconditionallyThrows(bytecode)) {
     if (IsFirstUpdate) {
       // On first update, we can assume that this out-liveness is the same as
       // the next liveness, and can directly alias it -- we'll allocate a new

src/interpreter/bytecodes.h

@@ -537,6 +537,10 @@ namespace interpreter {
   V(Return)                     \
   V(SuspendGenerator)
 
+#define UNCONDITIONAL_THROW_BYTECODE_LIST(V) \
+  V(Throw)                                   \
+  V(ReThrow)
+
 // Enumeration of interpreter bytecodes.
 enum class Bytecode : uint8_t {
 #define DECLARE_BYTECODE(Name, ...) k##Name,
@@ -801,6 +805,13 @@ class V8_EXPORT_PRIVATE Bytecodes final : public AllStatic {
 #undef OR_BYTECODE
   }
 
+  // Returns true if the bytecode unconditionally throws.
+  static constexpr bool UnconditionallyThrows(Bytecode bytecode) {
+#define OR_BYTECODE(NAME) || bytecode == Bytecode::k##NAME
+    return false UNCONDITIONAL_THROW_BYTECODE_LIST(OR_BYTECODE);
+#undef OR_BYTECODE
+  }
+
   // Returns the number of operands expected by |bytecode|.
   static int NumberOfOperands(Bytecode bytecode) {
     DCHECK_LE(bytecode, Bytecode::kLast);