llvm dev - Dec 2015 - Help with new llvm.debug.value metadata API

Hi all,

So I started working on upgrading our tool from LLVM 3.5 to 3.6, and I
would appreciate your help with the new metadata API.

In particular, I currently have the following snippet of code:
// ci is llvm.debug.value instruction
    const llvm::MDNode* m1 = dyn_cast<const
llvm::MDNode>(ci.getArgOperand(0));
    const llvm::MDNode* m2 = dyn_cast<const
llvm::MDNode>(ci.getArgOperand(2));
    assert(m1 && "Expected metadata node in first argument to
llvm.dbg.value.");
    assert(m2 && "Expected metadata node in third argument to
llvm.dbg.value.");
    const llvm::MDString* m3 = dyn_cast<const
llvm::MDString>(m2->getOperand(2));
    assert(m3 && "Expected metadata string in the third argument to
metadata node.");

   if (const llvm::Value* V = m1->getOperand(0)) { // this does not compile
any more!
   ... Need Type of Value V here.
    }

In LLVM 3.6, the expression in the if condition does not compile any more.

What I basically need in the if body is to access the type (Type) of the
variable specified in the llvm.debug.value metadata. How do I access its
type using the new metadata API?

Any pointers would be greatly appreciated.

Thanks!
-- Zvonimir
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> On Dec 22, 2015, at 6:53 AM, Zvonimir Rakamaric via llvm-dev <llvm-dev
at lists.llvm.org> wrote:
> 
> Hi all,
> 
> So I started working on upgrading our tool from LLVM 3.5 to 3.6, and I
would appreciate your help with the new metadata API.
> 
> In particular, I currently have the following snippet of code:
> // ci is llvm.debug.value instruction
>     const llvm::MDNode* m1 = dyn_cast<const
llvm::MDNode>(ci.getArgOperand(0));
>     const llvm::MDNode* m2 = dyn_cast<const
llvm::MDNode>(ci.getArgOperand(2));
>     assert(m1 && "Expected metadata node in first argument to
llvm.dbg.value.");
>     assert(m2 && "Expected metadata node in third argument to
llvm.dbg.value.");
>     const llvm::MDString* m3 = dyn_cast<const
llvm::MDString>(m2->getOperand(2));
>     assert(m3 && "Expected metadata string in the third
argument to metadata node.");
> 
>    if (const llvm::Value* V = m1->getOperand(0)) { // this does not
compile any more!
>    ... Need Type of Value V here.
>     }
> 
> In LLVM 3.6, the expression in the if condition does not compile any more.
> 
> What I basically need in the if body is to access the type (Type) of the
variable specified in the llvm.debug.value metadata. How do I access its type
using the new metadata API?
There are now convenient accessors to do all of this:

http://www.llvm.org/docs/doxygen/html/classllvm_1_1DbgValueInst.html

You’ll probably want:
   resolve(ci->getVariable()->getType())

-- adrian
> 
> Any pointers would be greatly appreciated.
> 
> Thanks!
> -- Zvonimir
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Hi Zvonimir,
> Hi all,
> 
> So I started working on upgrading our tool from LLVM 3.5 to 3.6, and I
would appreciate your help with the new metadata API.
> 
> In particular, I currently have the following snippet of code:
> // ci is llvm.debug.value instruction
>     const llvm::MDNode* m1 = dyn_cast<const
llvm::MDNode>(ci.getArgOperand(0));
>     const llvm::MDNode* m2 = dyn_cast<const
llvm::MDNode>(ci.getArgOperand(2));
>     assert(m1 && "Expected metadata node in first argument to
llvm.dbg.value.");
>     assert(m2 && "Expected metadata node in third argument to
llvm.dbg.value.");
>     const llvm::MDString* m3 = dyn_cast<const
llvm::MDString>(m2->getOperand(2));
>     assert(m3 && "Expected metadata string in the third
argument to metadata node.");
> 
>    if (const llvm::Value* V = m1->getOperand(0)) { // this does not
compile any more!
>    ... Need Type of Value V here.
>     }
> 
> In LLVM 3.6, the expression in the if condition does not compile any more.
It looks like MDNode::getOperand() returns `const MDOperand &` now, not
`Value *`.

> What I basically need in the if body is to access the type (Type) of the
variable specified in the llvm.debug.value metadata. How do I access its type
using the new metadata API?
I haven't tried this, but I suspect you'd need something like:

  if (auto *VAM =
dyn_cast<llvm::ValueAsMetadata>(m1->getOperand(0).get())) {
    // VAM->getType()
  }

This should be documented in:

  http://llvm.org/docs/doxygen/html/classllvm_1_1MDNode.html


best
vedant