Request for review (L): 6378821: where available, bitCount() should use POPC on SPARC processors and AMD+10h

[Tom Rodriguez]

The PopCount nodes should only take one argument since they are never  
required to have control.

I think there are problems with register usage with PopCountL in  
x86_32.ad.  USEs (inputs) and TEMPs are guaranteed to be different  
registers but DEFs are not.  KILLs and DEFs are guaranteed to be  
different.  The model of register interference is like a single  
hardware instruction where all the effects occur simultaneously so the  
DEFs and USEs can't interfere.  So for this:

+instruct popCountL(eRegI dst, eRegL src, eRegI tmp, eFlagsReg cr) %{
+  match(Set dst (PopCountL src));
+  effect(KILL cr, TEMP tmp);

dst isn't required to be different than src or tmp which will break  
you code generation.  If you add TEMP dst to the effects then the  
register allocator will make the output interfere with the inputs so  
you can use it as a temp in the code generation.  The memory one has  
the same problem.

Otherwise this looks good.

tom

On Mar 12, 2009, at 10:21 AM, Christian Thalinger wrote:

> http://cr.openjdk.java.net/~twisti/6378821/webrev.00/
>