RFR: 8252505: C1/C2 compiler support for blackholes [v11]
Aleksey Shipilev
shade at redhat.com
Thu Dec 3 11:45:06 UTC 2020
On 12/2/20 6:21 PM, Vladimir Ivanov wrote:
>
>> So where do we go from here? Somehow recording the operands of
>> MachCallBlackhole?
>
> Have you tried `PhaseRegAlloc::dump_register(const Node *n, char *buf)`
> on argument inputs?
Yes, new commit has it. For the sample method like:
public void test_08(Blackhole bh) {
bh.consume(x + y);
bh.consume(x + y);
...
-XX:+PrintOptoAssembly finally looks like this:
02c movl R11, [RSI + #16 (8-bit)] # int ! Field: org/openjdk/jmh/samples/XplusY.y
030 addl R11, [RSI + #12 (8-bit)] # int
034 blackhole RDX, R11
034 movl R11, [RSI + #16 (8-bit)] # int ! Field: org/openjdk/jmh/samples/XplusY.y
038 addl R11, [RSI + #12 (8-bit)] # int
03c blackhole RDX, R11
RDX is receiver ("bh"), and R11 is "x + y".
--
Thanks,
-Aleksey
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