[LLVMdev] redundant checking of terminator in Verifier?

[Chris Lattner]

On Jun 25, 2010, at 8:47 AM, Jianzhou Zhao wrote:

> Hi,
> 
> The checking about that if this is a terminator that it is at the end
> of the block has been applied twice (bellow). One is at
> Verifier::visitInstruction, and the other is at
> Verifier::visitTerminatorInst. Since visitInstruction is called when
> visiting each instruction, the checking at visitTerminatorInst seems
> redundant to me. Did I miss any case?

These are checking two subtly different things.  The first one is checking that there isn't a terminator in the middle of the block, the second is checking that there is a terminator at the end of a block.

-Chris

> 
> void Verifier::visitInstruction(Instruction &I) {
> ...
> line 1356:
>  // Verify that if this is a terminator that it is at the end of the block.
>  if (isa<TerminatorInst>(I))
>    Assert1(BB->getTerminator() == &I, "Terminator not at end of block!", &I);
> ...
> }
> 
> void Verifier::visitTerminatorInst(TerminatorInst &I) {
>  // Ensure that terminators only exist at the end of the basic block.
>  Assert1(&I == I.getParent()->getTerminator(),
>          "Terminator found in the middle of a basic block!", I.getParent());
>  visitInstruction(I);
> }
> 
> -- 
> Jianzhou
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