[LLVMdev] X86 -tailcallopt and C calling conversion

[Evan Cheng]

On Jan 1, 2011, at 4:20 PM, NAKAMURA Takumi wrote:

> Happy 2011, everybody!
> 
> It seems -tailcallopt prevents tailcall optimization when both caller
> and callee have ccc,
> even when it is optimized without an option -tailcallopt.

Sorry, I don't understand your question. What do you mean by both caller and callee have ccc?

Evan

> Is it intended or misoptimized?
> 
> In X86ISelLowering.cpp:X86TargetLowering::IsEligibleForTailCallOptimization():
> 
>  if (GuaranteedTailCallOpt) {
>    if (IsTailCallConvention(CalleeCC) && CCMatch)
>      return true;
>    return false;
>  }
> 
> I know -tailcallopt changes calling conversion of fastcc to callee-pop.
> 
> ps. I am tweaking tailcallopt on Win64.
> 
> ...Takumi
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