Sub-word comparisons

[Andrew Haley]

On 03/11/16 19:18, Doug Simon wrote:

> The lowering of a CompareNode to a CompareOp is AArch64 specific as
> far as I can see. This originates from the AArch64 implementations
> of LIRGenerator.emitCompareBranch and
> LIRGenerator.emitConditionalMove. You’ll have to change those
> methods to generate LIR ops that AArch64 actually supports.

Oh sure, I can do that, but that wasn't my problem, it was how to stop
Graal from creating sub-word comparisons in the first place.  Such
operations aren't part of the JVM at all, but are generated when the
bytecode is canonicalized.  I can generate code for sub-word
comparisons, but it won't be good code.  AArch64 is designed to work
well for languages like C and Java, which don't have any arithmetic
operations on sub-word types.

Andrew.