Integrated: 8257531: Super word not applied to a loop of simple Buffer operations

[Vladimir Kozlov]

On Fri, 4 Dec 2020 07:28:05 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

> In Buffer case there is additional (loop invariant) load from java/nio/IntBuffer.offset field.
> SuperWord did not handle loop's invariants in complex address expressions (only when vectorization is forced):
> 
> `AddP(addr, AddP(addr, addr, LShiftL(ConvI2L(CastII(AddI(AddI(iv_phi, invariant_LoadI), incr))), shift)), 16)`
> 
> Invariant reference is used to make sure all memory accesses in vectors use the same one. And only when alignment code is generated in pre-loop it is used for code generatin. But that code did not take into account that invariant have to be scaled if needed as in this example (invariant_LoadI << shift).
> 
> I propose to record scaling (left shift) for invariant when it is present and use it to compare invariants and in pre-loop alignment code generation. I also slightly modified tracing output code for invariants.
> 
> This allow vectorize Java code which uses Buffer.
> 
> I added new test based on @PaulSandoz example. It tests presence of new vectors and correctness of vectorized code.
> I included case (ByteBuffer.allocateDirect()) which is not vectorized because it uses Unsafe access - SuperWord complains about CastX2P(AddL) nodes which it sees instead of AddP.  We may consider vectorizing such code too later.
> 
> Testing: tier1-4, precheckin-comp (-Xcomp), renaissance test

This pull request has now been integrated.

Changeset: dd0b9454
Author:    Vladimir Kozlov <kvn at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/dd0b9454
Stats:     270 lines in 3 files changed: 247 ins; 2 del; 21 mod

8257531: Super word not applied to a loop of simple Buffer operations

Reviewed-by: roland, psandoz

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PR: https://git.openjdk.java.net/jdk/pull/1618