commit e15ea086439b41a805d164d2beb07b4ba96aaa97
author Hiroshi Yamauchi <yamauchi@google.com> Mon Feb 09 17:11:42 2015 -0800
committer Hiroshi Yamauchi <yamauchi@google.com> Tue Mar 03 17:33:18 2015 -0800
tree 465ee3780acd8b7cb35c8a7f42a1f3c5df3d26ec
parent 0b25c71ac93fb10c484dbacb9e23db505a8e2353

Reserve bits in the lock word for read barriers.

This prepares for the CC collector to use the standard object header
model by storing the read barrier state in the lock word.

Bug: 19355854
Bug: 12687968
Change-Id: Ia7585662dd2cebf0479a3e74f734afe5059fb70f

compiler/dex/quick/arm64/call_arm64.cc

diff --git a/compiler/dex/quick/arm64/call_arm64.cc b/compiler/dex/quick/arm64/call_arm64.cc
index 24e8fdf..15edcc5 100644
--- a/compiler/dex/quick/arm64/call_arm64.cc
+++ b/compiler/dex/quick/arm64/call_arm64.cc
@@ -172,7 +172,12 @@
   OpRegRegImm(kOpAdd, rs_x2, rs_x0, mirror::Object::MonitorOffset().Int32Value());
   NewLIR2(kA64Ldxr2rX, rw3, rx2);
   MarkPossibleNullPointerException(opt_flags);
-  LIR* not_unlocked_branch = OpCmpImmBranch(kCondNe, rs_w3, 0, NULL);
+  // Zero out the read barrier bits.
+  OpRegRegImm(kOpAnd, rs_w2, rs_w3, LockWord::kReadBarrierStateMaskShiftedToggled);
+  LIR* not_unlocked_branch = OpCmpImmBranch(kCondNe, rs_w2, 0, NULL);
+  // w3 is zero except for the rb bits here. Copy the read barrier bits into w1.
+  OpRegRegReg(kOpOr, rs_w1, rs_w1, rs_w3);
+  OpRegRegImm(kOpAdd, rs_x2, rs_x0, mirror::Object::MonitorOffset().Int32Value());
   NewLIR3(kA64Stxr3wrX, rw3, rw1, rx2);
   LIR* lock_success_branch = OpCmpImmBranch(kCondEq, rs_w3, 0, NULL);
 
@@ -217,13 +222,28 @@
     }
   }
   Load32Disp(rs_xSELF, Thread::ThinLockIdOffset<8>().Int32Value(), rs_w1);
-  Load32Disp(rs_x0, mirror::Object::MonitorOffset().Int32Value(), rs_w2);
+  if (!kUseReadBarrier) {
+    Load32Disp(rs_x0, mirror::Object::MonitorOffset().Int32Value(), rs_w2);
+  } else {
+    OpRegRegImm(kOpAdd, rs_x3, rs_x0, mirror::Object::MonitorOffset().Int32Value());
+    NewLIR2(kA64Ldxr2rX, rw2, rx3);
+  }
   MarkPossibleNullPointerException(opt_flags);
-  LIR* slow_unlock_branch = OpCmpBranch(kCondNe, rs_w1, rs_w2, NULL);
+  // Zero out the read barrier bits.
+  OpRegRegImm(kOpAnd, rs_w3, rs_w2, LockWord::kReadBarrierStateMaskShiftedToggled);
+  // Zero out except the read barrier bits.
+  OpRegRegImm(kOpAnd, rs_w2, rs_w2, LockWord::kReadBarrierStateMaskShifted);
+  LIR* slow_unlock_branch = OpCmpBranch(kCondNe, rs_w3, rs_w1, NULL);
   GenMemBarrier(kAnyStore);
-  Store32Disp(rs_x0, mirror::Object::MonitorOffset().Int32Value(), rs_wzr);
-  LIR* unlock_success_branch = OpUnconditionalBranch(NULL);
-
+  LIR* unlock_success_branch;
+  if (!kUseReadBarrier) {
+    Store32Disp(rs_x0, mirror::Object::MonitorOffset().Int32Value(), rs_w2);
+    unlock_success_branch = OpUnconditionalBranch(NULL);
+  } else {
+    OpRegRegImm(kOpAdd, rs_x3, rs_x0, mirror::Object::MonitorOffset().Int32Value());
+    NewLIR3(kA64Stxr3wrX, rw1, rw2, rx3);
+    unlock_success_branch = OpCmpImmBranch(kCondEq, rs_w1, 0, NULL);
+  }
   LIR* slow_path_target = NewLIR0(kPseudoTargetLabel);
   slow_unlock_branch->target = slow_path_target;
   if (null_check_branch != nullptr) {