8371205: AArch64: Remove unused cmpxchg* methods

Co-authored-by: Samuel Chee <[email protected]>
Reviewed-by: aph, kbarrett, haosun

Author: spchee

src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp

@@ -3315,97 +3315,6 @@ void MacroAssembler::reinit_heapbase()
   }
 }
 
-// this simulates the behaviour of the x86 cmpxchg instruction using a
-// load linked/store conditional pair. we use the acquire/release
-// versions of these instructions so that we flush pending writes as
-// per Java semantics.
-
-// n.b the x86 version assumes the old value to be compared against is
-// in rax and updates rax with the value located in memory if the
-// cmpxchg fails. we supply a register for the old value explicitly
-
-// the aarch64 load linked/store conditional instructions do not
-// accept an offset. so, unlike x86, we must provide a plain register
-// to identify the memory word to be compared/exchanged rather than a
-// register+offset Address.
-
-void MacroAssembler::cmpxchgptr(Register oldv, Register newv, Register addr, Register tmp,
-                                Label &succeed, Label *fail) {
-  // oldv holds comparison value
-  // newv holds value to write in exchange
-  // addr identifies memory word to compare against/update
-  if (UseLSE) {
-    mov(tmp, oldv);
-    casal(Assembler::xword, oldv, newv, addr);
-    cmp(tmp, oldv);
-    br(Assembler::EQ, succeed);
-    membar(AnyAny);
-  } else {
-    Label retry_load, nope;
-    prfm(Address(addr), PSTL1STRM);
-    bind(retry_load);
-    // flush and load exclusive from the memory location
-    // and fail if it is not what we expect
-    ldaxr(tmp, addr);
-    cmp(tmp, oldv);
-    br(Assembler::NE, nope);
-    // if we store+flush with no intervening write tmp will be zero
-    stlxr(tmp, newv, addr);
-    cbzw(tmp, succeed);
-    // retry so we only ever return after a load fails to compare
-    // ensures we don't return a stale value after a failed write.
-    b(retry_load);
-    // if the memory word differs we return it in oldv and signal a fail
-    bind(nope);
-    membar(AnyAny);
-    mov(oldv, tmp);
-  }
-  if (fail)
-    b(*fail);
-}
-
-void MacroAssembler::cmpxchg_obj_header(Register oldv, Register newv, Register obj, Register tmp,
-                                        Label &succeed, Label *fail) {
-  assert(oopDesc::mark_offset_in_bytes() == 0, "assumption");
-  cmpxchgptr(oldv, newv, obj, tmp, succeed, fail);
-}
-
-void MacroAssembler::cmpxchgw(Register oldv, Register newv, Register addr, Register tmp,
-                                Label &succeed, Label *fail) {
-  // oldv holds comparison value
-  // newv holds value to write in exchange
-  // addr identifies memory word to compare against/update
-  // tmp returns 0/1 for success/failure
-  if (UseLSE) {
-    mov(tmp, oldv);
-    casal(Assembler::word, oldv, newv, addr);
-    cmp(tmp, oldv);
-    br(Assembler::EQ, succeed);
-    membar(AnyAny);
-  } else {
-    Label retry_load, nope;
-    prfm(Address(addr), PSTL1STRM);
-    bind(retry_load);
-    // flush and load exclusive from the memory location
-    // and fail if it is not what we expect
-    ldaxrw(tmp, addr);
-    cmp(tmp, oldv);
-    br(Assembler::NE, nope);
-    // if we store+flush with no intervening write tmp will be zero
-    stlxrw(tmp, newv, addr);
-    cbzw(tmp, succeed);
-    // retry so we only ever return after a load fails to compare
-    // ensures we don't return a stale value after a failed write.
-    b(retry_load);
-    // if the memory word differs we return it in oldv and signal a fail
-    bind(nope);
-    membar(AnyAny);
-    mov(oldv, tmp);
-  }
-  if (fail)
-    b(*fail);
-}
-
 // A generic CAS; success or failure is in the EQ flag.  A weak CAS
 // doesn't retry and may fail spuriously.  If the oldval is wanted,
 // Pass a register for the result, otherwise pass noreg.

src/hotspot/cpu/aarch64/macroAssembler_aarch64.hpp

@@ -1200,16 +1200,6 @@ class MacroAssembler: public Assembler {
 
   void cmpoop(Register obj1, Register obj2);
 
-  // Various forms of CAS
-
-  void cmpxchg_obj_header(Register oldv, Register newv, Register obj, Register tmp,
-                          Label &succeed, Label *fail);
-  void cmpxchgptr(Register oldv, Register newv, Register addr, Register tmp,
-                  Label &succeed, Label *fail);
-
-  void cmpxchgw(Register oldv, Register newv, Register addr, Register tmp,
-                  Label &succeed, Label *fail);
-
   void atomic_add(Register prev, RegisterOrConstant incr, Register addr);
   void atomic_addw(Register prev, RegisterOrConstant incr, Register addr);
   void atomic_addal(Register prev, RegisterOrConstant incr, Register addr);