[SPARC] Cleanup handling of the Y/ASR registers.

- Implement copying ASR to/from GPR regs.
- Mark ASRs as non-allocatable, so it won't try to arbitrarily use
  them inappropriately.
- Instead of inserting explicit WRASR/RDASR nodes in the MUL/DIV
  routines, just do normal register copies.
- Also...mark div as using Y, not just writing it.

Added a test case with some code which previously died with an
assertion failure (with -O0), or produced wrong code (otherwise).

(Third time's the charm?)

Differential Revision: http://reviews.llvm.org/D10401

llvm-svn: 241686
diff --git a/llvm/test/CodeGen/SPARC/basictest.ll b/llvm/test/CodeGen/SPARC/basictest.ll
index 7b54007..3792100 100644
--- a/llvm/test/CodeGen/SPARC/basictest.ll
+++ b/llvm/test/CodeGen/SPARC/basictest.ll
@@ -38,7 +38,7 @@
 
 ; CHECK-LABEL: signed_divide:
 ; CHECK: sra %o0, 31, %o2
-; CHECK: wr %o2, %g0, %y
+; CHECK: wr %g0, %o2, %y
 ; CHECK: sdiv %o0, %o1, %o0
 define i32 @signed_divide(i32 %a, i32 %b) {
   %r = sdiv i32 %a, %b