tree 04df22eecc061cf808aa3a7a8a33ba02dc2b8ebf
parent 52d65ab72dcdb3b5de8b84743537355067819c31
author Tim Northover <tnorthover@apple.com> 1369919982 +0000
committer Tim Northover <tnorthover@apple.com> 1369919982 +0000

X86: use sub-register sequences for MOV*r0 operations

Instead of having a bunch of separate MOV8r0, MOV16r0, ... pseudo-instructions,
it's better to use a single MOV32r0 (which will expand to "xorl %reg, %reg")
and obtain other sizes with EXTRACT_SUBREG and SUBREG_TO_REG. The encoding is
smaller and partial register updates can sometimes be avoided.

Until recently, this sequence was a barrier to rematerialization though. That
should now be fixed so it's an appropriate time to make the change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182928 91177308-0d34-0410-b5e6-96231b3b80d8