[WIP - JEP 491] Loom: s390 Port

There are couple of traps which are part of JEP 491. So unexpected crash are to expected.

Author: offamitkumar

src/hotspot/cpu/s390/abstractInterpreter_s390.cpp

@@ -197,7 +197,8 @@ void AbstractInterpreter::layout_activation(Method* method,
     assert(is_bottom_frame && (sender_sp == caller->unextended_sp()),
            "must initialize sender_sp of bottom skeleton frame when pushing it");
   } else {
-    assert(caller->is_entry_frame() || caller->is_upcall_stub_frame(), "is there a new frame type??");
+    // FIXME: sender_sp correctly calculated for native frames ?
+    assert(caller->is_entry_frame() || caller->is_upcall_stub_frame() || caller->is_native_frame(), "is there a new frame type??");
     sender_sp = caller->sp(); // Call_stub only uses it's fp.
   }
 

src/hotspot/cpu/s390/assembler_s390.hpp

@@ -3279,6 +3279,9 @@ class Assembler : public AbstractAssembler {
   static bool is_z_nop(address x) {
     return is_z_nop(* (short *) x);
   }
+  static bool is_z_illtrap(address x) {
+    return *(uint16_t*)x == 0u;
+  }
   static bool is_z_br(long x) {
     return is_z_bcr(x) && ((x & 0x00f0) == 0x00f0);
   }

src/hotspot/cpu/s390/c1_LIRAssembler_s390.cpp

@@ -511,6 +511,7 @@ void LIR_Assembler::call(LIR_OpJavaCall* op, relocInfo::relocType rtype) {
   __ z_nop();
   __ z_brasl(Z_R14, op->addr());
   add_call_info(code_offset(), op->info());
+  __ post_call_nop();
 }
 
 void LIR_Assembler::ic_call(LIR_OpJavaCall* op) {
@@ -527,6 +528,7 @@ void LIR_Assembler::ic_call(LIR_OpJavaCall* op) {
   // to determine who we intended to call.
   __ relocate(virtual_call_Relocation::spec(virtual_call_oop_addr));
   call(op, relocInfo::none);
+  __ post_call_nop();
 }
 
 void LIR_Assembler::move_regs(Register from_reg, Register to_reg) {
@@ -2839,6 +2841,7 @@ void LIR_Assembler::rt_call(LIR_Opr result, address dest,
   if (info != nullptr) {
     add_call_info_here(info);
   }
+  __ post_call_nop();
 }
 
 void LIR_Assembler::volatile_move_op(LIR_Opr src, LIR_Opr dest, BasicType type, CodeEmitInfo* info) {

src/hotspot/cpu/s390/compiledIC_s390.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2026, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2016, 2019 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -29,17 +29,13 @@
 #include "memory/resourceArea.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/safepoint.hpp"
-#ifdef COMPILER2
-#include "opto/matcher.hpp"
-#endif
 
 // ----------------------------------------------------------------------------
 
 #undef  __
 #define __ masm->
 
 address CompiledDirectCall::emit_to_interp_stub(MacroAssembler *masm, address mark/* = nullptr*/) {
-#ifdef COMPILER2
   // Stub is fixed up when the corresponding call is converted from calling
   // compiled code to calling interpreted code.
   if (mark == nullptr) {
@@ -55,7 +51,7 @@ address CompiledDirectCall::emit_to_interp_stub(MacroAssembler *masm, address ma
   __ relocate(static_stub_Relocation::spec(mark));
 
   AddressLiteral meta = __ allocate_metadata_address(nullptr);
-  bool success = __ load_const_from_toc(as_Register(Matcher::inline_cache_reg_encode()), meta);
+  bool success = __ load_const_from_toc(Z_inline_cache, meta);
 
   __ set_inst_mark();
   AddressLiteral a((address)-1);
@@ -67,10 +63,6 @@ address CompiledDirectCall::emit_to_interp_stub(MacroAssembler *masm, address ma
   __ z_br(Z_R1);
   __ end_a_stub(); // Update current stubs pointer and restore insts_end.
   return stub;
-#else
-  ShouldNotReachHere();
-  return nullptr;
-#endif
 }
 
 #undef __

src/hotspot/cpu/s390/continuationEntry_s390.hpp

@@ -25,8 +25,11 @@
 #ifndef CPU_S390_CONTINUATIONENTRY_S390_HPP
 #define CPU_S390_CONTINUATIONENTRY_S390_HPP
 
+#include "runtime/frame.hpp"
+
 class ContinuationEntryPD {
-  // empty
+  // This is needed to position the ContinuationEntry at the unextended sp of the entry frame
+  frame::z_abi_160_base _abi;
 };
 
 #endif // CPU_S390_CONTINUATIONENTRY_S390_HPP

src/hotspot/cpu/s390/continuationEntry_s390.inline.hpp

@@ -25,22 +25,26 @@
 #ifndef CPU_S390_CONTINUATIONENTRY_S390_INLINE_HPP
 #define CPU_S390_CONTINUATIONENTRY_S390_INLINE_HPP
 
+#include "oops/method.inline.hpp"
+#include "runtime/frame.inline.hpp"
+#include "runtime/registerMap.hpp"
+#include "utilities/macros.hpp"
 #include "runtime/continuationEntry.hpp"
 
-// TODO: Implement
-
 inline frame ContinuationEntry::to_frame() const {
-  Unimplemented();
-  return frame();
+  static CodeBlob* cb = CodeCache::find_blob_fast(entry_pc());
+  assert(cb != nullptr, "");
+  assert(cb->as_nmethod()->method()->is_continuation_enter_intrinsic(), "");
+  return frame(entry_sp(), entry_pc(), entry_sp(), entry_fp(), cb);
 }
 
 inline intptr_t* ContinuationEntry::entry_fp() const {
-  Unimplemented();
-  return nullptr;
+  return (intptr_t*)((address)this + size());
 }
 
 inline void ContinuationEntry::update_register_map(RegisterMap* map) const {
-  Unimplemented();
+  // TODO: need to revisit
+  // Nothing to do (no non-volatile registers in java calling convention)
 }
 
 #endif // CPU_S390_CONTINUATIONENTRY_S390_INLINE_HPP