Avoid control flow for copying heap allocations to temporaries #8364
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Andrew @andrewcraik, may I ask you to review this change? |
Updates of all the temporaries that contain the address of a candidate object for cold block heapification are currently guarded with ifacmpne instructions. In order to simplify the control flow graph produced for heapification before cold blocks, replace the conditional update of each temporary with an unconditional store using the result of an aternary instruction that either updates the temporary with the heap object address or with the current contents of the temporary unconditionally. This update is inserted into the start of the cold block rather than in a new block preceding the cold block. This is only done if code generation supports ternary opcodes. If ternary opcodes are not supported, ifacmpne checks are still generated instead. The ifacmpne checks can also be forced by setting the environment variable TR_disableTernaryOpForEA. Signed-off-by: Henry Zongaro <zongaro@ca.ibm.com>
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Andrew @andrewcraik, I've squashed the two commits into one. By the way, I know there are pull requests #7797 and eclipse/omr#4578 outstanding for renaming the |
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#7797 is dependent on eclipse/omr#4578 so is marked WIP. 4578 is still under review while I think this is pretty much ready. I am going to start sanity and unless there are objections from @alvee-unb or @0xdaryl I feel this should merge once ready and that mans #7797 will need to be updated... If the rename lands before we are ready then the update to this PR will not be significant to handle the name change. |
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Jenkins test sanity all jdk11 |
Updates of all the temporaries that contain the address of a candidate object for cold block heapification are currently guarded with
ifacmpneinstructions. In order to simplify the control flow graph produced for heapification before cold blocks, replace the conditional update of eachtemporary with an unconditional store using the result of an
aternaryinstruction that either updates the temporary with the heap object address or with the current contents of the temporary unconditionally. This update is inserted into the start of the cold block rather than ina new block preceding the cold block.
This is only done if code generation supports ternary opcodes. If ternary opcodes are not supported,
ifacmpnechecks are still generated instead. Theifacmpnechecks can also be forced by setting the environment variableTR_disableTernaryOpForEA.Signed-off-by: Henry Zongaro zongaro@ca.ibm.com