[llvm-commits] Fwd: Re: [LLVMdev] [PATCH] Fix for bug in JIT exception table allocation

[Duncan Sands]

Hi Michael,

> --- lib/ExecutionEngine/JIT/JITEmitter.cpp	(revision 163478)
> +++ lib/ExecutionEngine/JIT/JITEmitter.cpp	(working copy)
> @@ -974,14 +974,24 @@
>      SavedBufferBegin = BufferBegin;
>      SavedBufferEnd = BufferEnd;
>      SavedCurBufferPtr = CurBufferPtr;
> +    uint8_t *FrameRegister;
>
> -    BufferBegin = CurBufferPtr = MemMgr->startExceptionTable(F.getFunction(),
> -                                                             ActualSize);
> -    BufferEnd = BufferBegin+ActualSize;
> -    EmittedFunctions[F.getFunction()].ExceptionTable = BufferBegin;
> -    uint8_t *EhStart;
> -    uint8_t *FrameRegister = DE->EmitDwarfTable(F, *this, FnStart, FnEnd,
> -                                                EhStart);
> +    while (true) {
> +      BufferBegin = CurBufferPtr = MemMgr->startExceptionTable(F.getFunction(),
> +                                                              ActualSize);
> +      BufferEnd = BufferBegin+ActualSize;
> +      EmittedFunctions[F.getFunction()].ExceptionTable = BufferBegin;
> +      uint8_t *EhStart;
> +      FrameRegister = DE->EmitDwarfTable(F, *this, FnStart, FnEnd, EhStart);
> +
> +      // If we've run out of memory, try again with twice as much space.
> +      if (CurBufferPtr == BufferEnd) {
> +        ActualSize = (CurBufferPtr-BufferBegin)*2;
> +        MemMgr->deallocateExceptionTable(BufferBegin);
> +      } else {
> +        break;
> +      }

here I think it would be more conformant with LLVM style to do:

        // If the buffer was large enough to hold the table then we are done.
        if (CurBufferPtr != BufferEnd)
          break;

        // Try again with twice as much space.
        ActualSize = (CurBufferPtr-BufferBegin)*2;
        MemMgr->deallocateExceptionTable(BufferBegin);

Otherwise looks good to me, though that's not saying much since I don't know
this part of LLVM.

Ciao, Duncan.

> +    }
>      MemMgr->endExceptionTable(F.getFunction(), BufferBegin, CurBufferPtr,
>                                FrameRegister);
>      BufferBegin = SavedBufferBegin;