6884973: java -XX:Atomics=2 crashes

Summary: Remove buggy experimental option
Reviewed-by: acorn, coleenp
Contributed-by: harold.seigel@oracle.com

src/cpu/x86/vm/assembler_x86.cpp

@@ -1170,26 +1170,11 @@ void Assembler::cmpw(Address dst, int imm16) {
 // and stores reg into adr if so; otherwise, the value at adr is loaded into rax,.
 // The ZF is set if the compared values were equal, and cleared otherwise.
 void Assembler::cmpxchgl(Register reg, Address adr) { // cmpxchg
-  if (Atomics & 2) {
-     // caveat: no instructionmark, so this isn't relocatable.
-     // Emit a synthetic, non-atomic, CAS equivalent.
-     // Beware.  The synthetic form sets all ICCs, not just ZF.
-     // cmpxchg r,[m] is equivalent to rax, = CAS (m, rax, r)
-     cmpl(rax, adr);
-     movl(rax, adr);
-     if (reg != rax) {
-        Label L ;
-        jcc(Assembler::notEqual, L);
-        movl(adr, reg);
-        bind(L);
-     }
-  } else {
   InstructionMark im(this);
   prefix(adr, reg);
   emit_byte(0x0F);
   emit_byte(0xB1);
   emit_operand(reg, adr);
-  }
 }
 
 void Assembler::comisd(XMMRegister dst, Address src) {
@@ -1513,12 +1498,7 @@ void Assembler::leal(Register dst, Address src) {
 }
 
 void Assembler::lock() {
-  if (Atomics & 1) {
-     // Emit either nothing, a NOP, or a NOP: prefix
-     emit_byte(0x90) ;
-  } else {
   emit_byte(0xF0);
-  }
 }
 
 void Assembler::lzcntl(Register dst, Register src) {

src/share/vm/runtime/globals.hpp

@@ -1066,9 +1066,6 @@ class CommandLineFlags {
                                                                             \
   product(bool, MonitorInUseLists, false, "Track Monitors for Deflation")   \
                                                                             \
-  product(intx, Atomics, 0,                                                 \
-          "(Unsafe,Unstable) Diagnostic - Controls emission of atomics")    \
-                                                                            \
   product(intx, SyncFlags, 0, "(Unsafe,Unstable) Experimental Sync flags" ) \
                                                                             \
   product(intx, SyncVerbose, 0, "(Unstable)" )                              \