[LLVMdev] JIT machine code deletion

[Chris Lattner]

On Sun, 14 May 2006, Ralph Corderoy wrote:
>> PPC should be 4 bytes in the normal case.  It is up to the backend to
>> implement this API correctly... if it doesn't, that's a bug: please
>> report it!
>
> No, EmitBranchToAt() always emits 16 bytes.
>
>    AtI[0] = BUILD_LIS(12, Addr >> 16);   // lis r12, hi16(address)
>    AtI[1] = BUILD_ORI(12, 12, Addr);     // ori r12, r12, low16(address)
>    AtI[2] = BUILD_MTCTR(12);             // mtctr r12
>    AtI[3] = BUILD_BCTR(isCall);          // bctr/bctrl
>
> but I understand now how startFunctionStub() is given StubSize and on
> PowerPC it's 16 so there's no problem.

Ah, that's silly.  If the source and target are within range (as they 
should almost always be), a simple unconditional branch should be used. 
Patches welcome :)

-Chris

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