llvm dev - Jun 2010 - [LLVMdev] redundant checking of terminator in Verifier?

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?

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

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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