[llvm-commits] [llvm] r52421 - /llvm/trunk/lib/CodeGen/LowerSubregs.cpp

[Chris Lattner]

On Jun 17, 2008, at 10:59 AM, Evan Cheng wrote:

> Author: evancheng
> Date: Tue Jun 17 12:59:16 2008
> New Revision: 52421
>
> URL: http://llvm.org/viewvc/llvm-project?rev=52421&view=rev
> Log:
> It's not safe to remove SUBREG_TO_REG that looks like identity  
> copies, e.g. movl %eax, %eax on x86-64 actually does a zero-extend.

It sounds like we need a "movl %eax, %eax" that is a copy, and a  
separate "movl %eax, %eax" machine instr that is a zeroextend.

-Chris