src/hotspot/cpu/x86/jniFastGetField_x86_64.cpp

rev 55834 : 8227680: FastJNIAccessors: Check for JVMTI field access event requests at runtime
Summary: Check JvmtiExport::_field_access_count != 0 at runtime
Reviewed-by: dholmes, eosterlund, bulasevich

*** 1,7 ****
  /*
!  * Copyright (c) 2004, 2017, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
--- 1,7 ----
  /*
!  * Copyright (c) 2004, 2019, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
*** 39,53 ****
  // rax/xmm0: result
  // c_rarg0:    jni env
  // c_rarg1:    obj
  // c_rarg2:    jfield id
  
! static const Register rtmp          = r8;
  static const Register robj          = r9;
! static const Register rcounter      = r10;
! static const Register roffset       = r11;
! static const Register rcounter_addr = r11;
  
  // Warning: do not use rip relative addressing after the first counter load
  // since that may scratch r10!
  
  address JNI_FastGetField::generate_fast_get_int_field0(BasicType type) {
--- 39,52 ----
  // rax/xmm0: result
  // c_rarg0:    jni env
  // c_rarg1:    obj
  // c_rarg2:    jfield id
  
! static const Register rtmp     = rax; // r8 == c_rarg2 on Windows
  static const Register robj     = r9;
! static const Register roffset  = r10;
! static const Register rcounter = r11;
  
  // Warning: do not use rip relative addressing after the first counter load
  // since that may scratch r10!
  
  address JNI_FastGetField::generate_fast_get_int_field0(BasicType type) {
*** 72,81 ****
--- 71,89 ----
    ExternalAddress counter(SafepointSynchronize::safepoint_counter_addr());
    __ mov32 (rcounter, counter);
    __ mov   (robj, c_rarg1);
    __ testb (rcounter, 1);
    __ jcc (Assembler::notZero, slow);
+ 
+   if (JvmtiExport::can_post_field_access()) {
+     // Check to see if a field access watch has been set before we
+     // take the fast path.
+     assert_different_registers(rscratch1, robj, rcounter); // cmp32 clobbers rscratch1!
+     __ cmp32(ExternalAddress((address) JvmtiExport::get_field_access_count_addr()), 0);
+     __ jcc(Assembler::notZero, slow);
+   }
+ 
    __ mov   (roffset, c_rarg2);
    __ shrptr(roffset, 2);                         // offset
  
    // Both robj and rtmp are clobbered by try_resolve_jobject_in_native.
    BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
*** 162,171 ****
--- 170,186 ----
    __ mov32 (rcounter, counter);
    __ mov   (robj, c_rarg1);
    __ testb (rcounter, 1);
    __ jcc (Assembler::notZero, slow);
  
+   if (JvmtiExport::can_post_field_access()) {
+     // Check to see if a field access watch has been set before we
+     // take the fast path.
+     __ cmp32(ExternalAddress((address) JvmtiExport::get_field_access_count_addr()), 0);
+     __ jcc(Assembler::notZero, slow);
+   }
+ 
    // Both robj and rtmp are clobbered by try_resolve_jobject_in_native.
    BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
    bs->try_resolve_jobject_in_native(masm, /* jni_env */ c_rarg0, robj, rtmp, slow);
    DEBUG_ONLY(__ movl(rtmp, 0xDEADC0DE);)