[liftoff][arm] Implement AssertUnreachable

This implements AssertUnreachable for the arm32 port of Liftoff.

Bug: v8:6600
Change-Id: I9aa5083dc1be175fc5f2f386d8aace021bab3b03
Reviewed-on: https://chromium-review.googlesource.com/c/1346335
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57767}

src/arm/macro-assembler-arm.cc

@@ -1884,6 +1884,10 @@ void TurboAssembler::Assert(Condition cond, AbortReason reason) {
     Check(cond, reason);
 }
 
+void TurboAssembler::AssertUnreachable(AbortReason reason) {
+  if (emit_debug_code()) Abort(reason);
+}
+
 void TurboAssembler::Check(Condition cond, AbortReason reason) {
   Label L;
   b(cond, &L);

src/arm/macro-assembler-arm.h

@@ -281,9 +281,13 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   void MovFromFloatResult(DwVfpRegister dst);
 
   // Calls Abort(msg) if the condition cond is not satisfied.
-  // Use --debug_code to enable.
+  // Use --debug-code to enable.
   void Assert(Condition cond, AbortReason reason);
 
+  // Like Assert(), but without condition.
+  // Use --debug-code to enable.
+  void AssertUnreachable(AbortReason reason);
+
   // Like Assert(), but always enabled.
   void Check(Condition cond, AbortReason reason);
 

src/wasm/baseline/arm/liftoff-assembler-arm.h

@@ -476,6 +476,7 @@ void LiftoffAssembler::FillI64Half(Register reg, uint32_t half_index) {
                                      Register rhs) {             \
     instruction(dst, lhs, rhs);                                  \
   }
+
 #define UNIMPLEMENTED_I64_BINOP(name)                                          \
   void LiftoffAssembler::emit_##name(LiftoffRegister dst, LiftoffRegister lhs, \
                                      LiftoffRegister rhs) {                    \
@@ -804,7 +805,8 @@ void LiftoffAssembler::CallTrapCallbackForTesting() {
 }
 
 void LiftoffAssembler::AssertUnreachable(AbortReason reason) {
-  BAILOUT("AssertUnreachable");
+  // Asserts unreachable within the wasm code.
+  TurboAssembler::AssertUnreachable(reason);
 }
 
 void LiftoffAssembler::PushRegisters(LiftoffRegList regs) {