[Beignet] [PATCH] GBE: skip current BB if it is not in a PN node's incoming BB list.

[Song, Ruiling]

> -----Original Message-----
> From: Beignet [mailto:beignet-bounces at lists.freedesktop.org] On Behalf Of
> Zhigang Gong
> Sent: Thursday, April 02, 2015 12:24 PM
> To: beignet at lists.freedesktop.org
> Cc: Gong, Zhigang
> Subject: [Beignet] [PATCH] GBE: skip current BB if it is not in a PN node's
> incoming BB list.
> 
> This is a possible situation especially for a complex switch case lowering.

Could you give me an example, according to llvm doc @lib/IR/Verifier.cpp
//  * PHI nodes must have an entry for each predecessor, with no extras.

I think if you add one verifier pass before genwriter, it could not pass verifier pass.
Does it occur only on special llvm version?

Thanks!
Ruiling
> 
> Signed-off-by: Zhigang Gong <zhigang.gong at intel.com>
> ---
>  backend/src/llvm/llvm_gen_backend.cpp | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/backend/src/llvm/llvm_gen_backend.cpp
> b/backend/src/llvm/llvm_gen_backend.cpp
> index 0487bcb..4008704 100644
> --- a/backend/src/llvm/llvm_gen_backend.cpp
> +++ b/backend/src/llvm/llvm_gen_backend.cpp
> @@ -1186,6 +1186,10 @@ namespace gbe
>    void GenWriter::emitMovForPHI(BasicBlock *curr, BasicBlock *succ) {
>      for (BasicBlock::iterator I = succ->begin(); isa<PHINode>(I); ++I) {
>        PHINode *PN = cast<PHINode>(I);
> +      // If current BB is not in the PN's incomming block list,
> +      // just skip it here.
> +      if (PN->getBasicBlockIndex(curr) < 0)
> +        continue;
>        Value *IV = PN->getIncomingValueForBlock(curr);
>        Type *llvmType = PN->getType();
>        const ir::Type type = getType(ctx, llvmType);
> --
> 1.9.1
> 
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