llvm dev - Jun 2011 - [LLVMdev] ARM instructions clobbering frame pointer

Someone hit a bug (not in bugs.llvm.org) caused by the non-Darwin call
instructions not being marked as using the frame pointer. Is it safe to just add
r11 / r7 as uses to the appropriate instructions like we do on Darwin? Does
anyone care about the slight pessimization this would cause in the
-fomit-frame-pointer case?

Thanks,
Cameron

On Jun 25, 2011, at 11:39 PM, Cameron Zwarich wrote:
> Someone hit a bug (not in bugs.llvm.org) caused by the non-Darwin call
instructions not being marked as using the frame pointer. Is it safe to just add
r11 / r7 as uses to the appropriate instructions like we do on Darwin? Does
anyone care about the slight pessimization this would cause in the
-fomit-frame-pointer case?
That sounds very odd, the frame pointer should be reserved so it shouldn't
matter who clobbers it.

Are you calling a function that uses a frame pointer from a function that omits
the frame pointer?

/jakob

On 2011-06-26, at 8:44 AM, Jakob Stoklund Olesen wrote:
> On Jun 25, 2011, at 11:39 PM, Cameron Zwarich wrote:
> 
>> Someone hit a bug (not in bugs.llvm.org) caused by the non-Darwin call
instructions not being marked as using the frame pointer. Is it safe to just add
r11 / r7 as uses to the appropriate instructions like we do on Darwin? Does
anyone care about the slight pessimization this would cause in the
-fomit-frame-pointer case?
> 
> That sounds very odd, the frame pointer should be reserved so it
shouldn't matter who clobbers it.
> 
> Are you calling a function that uses a frame pointer from a function that
omits the frame pointer?
I guess it's not actually a clobber of the FP. The various call instructions
are not marked as users of the FP, so post-RA scheduling will move the prologue
FP setup code after the function call.

Cameron