Why is vsldoi's SHB parameter signed?

[Doerr, Martin]

Hi Gustavo,

I also think that using unsigned would be more comprehensible. Feel free to change it to uimm with the next change which uses it. There are only a few places which will need to get updated.

Best regards,
Martin


-----Original Message-----
From: ppc-aix-port-dev [mailto:ppc-aix-port-dev-bounces at openjdk.java.net] On Behalf Of Gustavo Serra Scalet
Sent: Dienstag, 7. Februar 2017 19:11
To: ppc-aix-port-dev at openjdk.java.net
Subject: Why is vsldoi's SHB parameter signed?

Hi,

I noticed that vsldoi instruction parameter SHB is being checked as a signed argument of 4 bits:

assembler_ppc.inline.hpp:804:inline void Assembler::vsldoi(  VectorRegister d, VectorRegister a, VectorRegister b, int si4)         { emit_int32( VSLDOI_OPCODE| vrt(d) | vra(a) | vrb(b) | vsldoi_shb(simm(si4,4))); }

I wonder why it was not defined as an unsigned parameter of 4 bits as described by ISA (attached). Is there a different way to look at it?!

Thanks