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7190310: Inlining WeakReference.get(), and hoisting $referent may lead to non-terminating loops

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In C2 add software membar after load from Reference.referent field to prevent commoning of loads across safepoint since GC can change its value. In C1 always generate Reference.get() intrinsic.

Reviewed-by: roland, twisti, dholmes, johnc
This commit is contained in:
Vladimir Kozlov 2012-08-20 09:58:58 -07:00
parent e3c3c8527e
commit 04c6a7ce10
9 changed files with 333 additions and 300 deletions
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21
hotspot/src/share/vm/c1/c1_GraphBuilder.cpp
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@ -3058,7 +3058,7 @@ GraphBuilder::GraphBuilder(Compilation* compilation, IRScope* scope)
case vmIntrinsics::_Reference_get:
{
if (UseG1GC) {
{
// With java.lang.ref.reference.get() we must go through the
// intrinsic - when G1 is enabled - even when get() is the root
// method of the compile so that, if necessary, the value in
@ -3070,6 +3070,9 @@ GraphBuilder::GraphBuilder(Compilation* compilation, IRScope* scope)
// object removed from the list of discovered references during
// reference processing.
// Also we need intrinsic to prevent commoning reads from this field
// across safepoint since GC can change its value.
// Set up a stream so that appending instructions works properly.
ciBytecodeStream s(scope->method());
s.reset_to_bci(0);
@ -3226,7 +3229,6 @@ const char* GraphBuilder::should_not_inline(ciMethod* callee) const {
bool GraphBuilder::try_inline_intrinsics(ciMethod* callee) {
if (!InlineNatives ) INLINE_BAILOUT("intrinsic method inlining disabled");
if (callee->is_synchronized()) {
// We don't currently support any synchronized intrinsics
return false;
@ -3234,9 +3236,13 @@ bool GraphBuilder::try_inline_intrinsics(ciMethod* callee) {
// callee seems like a good candidate
// determine id
vmIntrinsics::ID id = callee->intrinsic_id();
if (!InlineNatives && id != vmIntrinsics::_Reference_get) {
// InlineNatives does not control Reference.get
INLINE_BAILOUT("intrinsic method inlining disabled");
}
bool preserves_state = false;
bool cantrap = true;
vmIntrinsics::ID id = callee->intrinsic_id();
switch (id) {
case vmIntrinsics::_arraycopy:
if (!InlineArrayCopy) return false;
@ -3376,11 +3382,10 @@ bool GraphBuilder::try_inline_intrinsics(ciMethod* callee) {
return true;
case vmIntrinsics::_Reference_get:
// It is only when G1 is enabled that we absolutely
// need to use the intrinsic version of Reference.get()
// so that the value in the referent field, if necessary,
// can be registered by the pre-barrier code.
if (!UseG1GC) return false;
// Use the intrinsic version of Reference.get() so that the value in
// the referent field can be registered by the G1 pre-barrier code.
// Also to prevent commoning reads from this field across safepoint
// since GC can change its value.
preserves_state = true;
break;