[LLVMdev] global type legalization?

[Bob Wilson]

On Aug 18, 2010, at 11:31 AM, Jakob Stoklund Olesen wrote:

> 
> On Aug 18, 2010, at 11:22 AM, Chris Lattner wrote:
> 
>> 
>> On Aug 18, 2010, at 11:13 AM, Jakob Stoklund Olesen wrote:
>> 
>>> 
>>> On Aug 18, 2010, at 9:56 AM, Chris Lattner wrote:
>>> 
>>>> Some things to consider: When the input to the zext is spilled, the reload can be folded into the zext on almost all targets, making the zext free.  When the zext *isn't* folded into a load, what you're really looking for is a code placement pass which tries to put the zexts in non-redundant (and non-partially redundant) places.
>>> 
>>> That makes sense to me, but note that this is not currently implemented. All our RISC-like targets only support folding of COPY to load/store through the target-independent mechanisms.
>>> 
>>> It should be fairly simple to add a foldMemoryOperandImpl override to ARM that folds load+zext into a zextload.
>> 
>> Really?  I'm pretty sure that ppc folded load into [sz]ext (with custom code).  If ARM isn't doing this, it should - it is a clear win.
> 
> It is entirely possible I broke it when I added the COPY instruction.
> 
> I deleted the RISC target hooks for foldMemoryOperandImpl, thinking that COPY folding was all they needed.

The issue I'm looking at predates your COPY changes:
<rdar://problem/7999181> values spilled to the stack should not need to be sign- or zero-extended