[PATCH] D17181: [X86] Don't turn (c?-v:v) into (c?-v:0) by blindly using PSIGN.

[Sanjay Patel via llvm-commits]

spatel added a comment.

In http://reviews.llvm.org/D17181#353035, @ab wrote:

> This also means that we can completely remove PSIGN, as this was the only user in the codebase. I'll do that when we agree.


Great! I didn't think it was worth the effort to optimize the codegen, but we did better than I initially thought we could. And deleting an X86-specific node is better still. psign...quite an instruction. :)

> > Side note: it's been 10 years since SSSE3 (Merom) came out...can we change the default x86 subtarget now from Yonah/SSE2?

> 

> 

> Heh, I would love to see that, but I guess that the hardware vendors (Sony, Apple?) changed it already, and most of the others (distros?) want to stick to the minimal meaning of "x86_64".


My memory was off - Yonah had SSE3:
https://en.wikipedia.org/wiki/Yonah_%28microprocessor%29

In any case, it looks like we default to "Core2" as our CPU model which actually is Merom, but then we limit it to SSE2. Seems odd. A Darwin x86 target required SSE3 from the start. There might be something to chase down here.


http://reviews.llvm.org/D17181