Vladimir,
Thanks for the feedback!
Updated webrev in place:
http://cr.openjdk.java.net/~vlivanov/8074548/webrev.00/
You already have 'result' variable for argument(0), why reread?:
CmpINode(argument(0)
Good point. Fixed.
Usually IfTrue is the fast path. IGVN will revert that check to have
that. But it is better to have it in code. Current code looks like
double negation.
Fixed.
There is no explanation in changes why false_count never seen (== 0) is
more important than true_count == 0. The comment says "one of the values".
The code is the following:
if (false_cnt == 0 || true_cnt == 0) {
// According to profile, one value has been never seen.
int expected_val = (false_cnt == 0) ? 1 : 0;
(false_cnt != 0) => (true_cnt == 0).
Do you want me to add additional comment about that?
I chose (false_cnt == 0) because it refers to "always true" case.
Best regards,
Vladimir Ivanov
Thanks,
Vladimir
On 3/16/15 11:26 AM, Vladimir Ivanov wrote:
http://cr.openjdk.java.net/~vlivanov/8074548/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8074548
MethodHandleImpl::profileBoolean doesn't update never-taken branch count
when hitting a deopt on it. As a result, for rarely taken branches
consequent compilations consider them as never-taken and prune them
again causing repeated deopts. It severely affects peak performance.
The fix is to update MHI::profileBoolean intrinsic to insert a guard and
uncommon trap w/ reexecute bit set for never-seen value. Once previously
never seen value is encountered, the execution resumes after deopt in
MHI::profileBoolean and corresponding count becomes non-zero.
The guard doesn't add any additional overhead, since it dominates all
value usages and all branches on the same value are eliminated.
Testing: java/lang/invoke, nashorn, octane
Best regards,
Vladimir Ivanov
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