llvm dev - Mar 2011 - [LLVMdev] indirectbr implementation for Alpha backend

Hi,

I encountered an error while trying to use the indirectbr instruction with
Alpha backend (current build).  Here's part of the code sequence that I
tried to compile:

bb1:
  %1 = load i32* %i, align 4
  %2 = add nsw i32 %1, 1
  store i32 %2, i32* %i, align 4
  indirectbr i8* blockaddress(@main, %bb1), [ label %bb1 ]
  br label %return

This compiles correctly when I use the X86 or PPC backend, but results in
the following error with Alpha backend:

LLVM ERROR: Cannot select: 0x95a0490: i64 = BlockAddress<@main, %bb1>
[ID=3]

I also found the following line commented out in the file
lib/Target/Alpha/AlphaISelLowering.cpp:

//  setOperationAction(ISD::BRIND,        MVT::Other,   Expand);

My guess is that indirectbr is not implemented for Alpha.  If that's the
case, where do I need to make changes to implement this instruction?

Thank you,

Giang
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On Thu, Mar 31, 2011 at 9:22 AM, Giang Hoang <ghoang84 at gmail.com>
wrote:
> Hi,
> I encountered an error while trying to use the indirectbr instruction with
> Alpha backend (current build).  Here's part of the code sequence that I
> tried to compile:
> bb1:
>   %1 = load i32* %i, align 4
>   %2 = add nsw i32 %1, 1
>   store i32 %2, i32* %i, align 4
>   indirectbr i8* blockaddress(@main, %bb1), [ label %bb1 ]
>   br label %return
> This compiles correctly when I use the X86 or PPC backend, but results in
> the following error with Alpha backend:
> LLVM ERROR: Cannot select: 0x95a0490: i64 = BlockAddress<@main, %bb1>
[ID=3]
> I also found the following line commented out in the file
> lib/Target/Alpha/AlphaISelLowering.cpp:
> //  setOperationAction(ISD::BRIND,        MVT::Other,   Expand);
> My guess is that indirectbr is not implemented for Alpha.  If that's
the
> case, where do I need to make changes to implement this instruction?
What is missing is lowering block addresses to target addresses.  Have
you tried uncommenting that line?  Otherwise lowering directly to a
target address (if that expansion doesn't) may work.

Andrew
> Thank you,
> Giang
>
>
>
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