[llvm] r269236 - SDAG: Add a helper to replace and remove a node during ISel

[H.J. Lu via llvm-commits]

On Wed, May 11, 2016 at 2:13 PM, Justin Bogner via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: bogner
> Date: Wed May 11 16:13:17 2016
> New Revision: 269236
>
> URL: http://llvm.org/viewvc/llvm-project?rev=269236&view=rev
> Log:
> SDAG: Add a helper to replace and remove a node during ISel
>
> It's very common to want to replace a node and then remove it since
> it's dead, especially as we port backends from the SDNode *Select API
> to the void Select one. This helper makes this sequence a bit less
> verbose.
>
> Modified:
>     llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h
>     llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp
>
> Modified: llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h?rev=269236&r1=269235&r2=269236&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h (original)
> +++ llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h Wed May 11 16:13:17 2016
> @@ -234,6 +234,11 @@ protected:
>      CurDAG->ReplaceAllUsesWith(F, T);
>    }
>
> +  /// Replace all uses of \c F with \c T, then remove \c F from the DAG.
> +  void ReplaceNode(SDNode *F, SDNode *T) {
> +    CurDAG->ReplaceAllUsesWith(F, T);
> +    CurDAG->RemoveDeadNode(F);
> +  }
>
>    /// SelectInlineAsmMemoryOperands - Calls to this are automatically generated
>    /// by tblgen.  Others should not call it.
>

Did you miss

 case ISD::BRIND: {
    if (Subtarget->isTargetNaCl())
      // NaCl has its own pass where jmp %r32 are converted to jmp %r64. We
      // leave the instruction alone.
      break;
    if (Subtarget->isTarget64BitILP32()) {
      // Converts a 32-bit register to a 64-bit, zero-extended version of
      // it. This is needed because x86-64 can do many things, but jmp %r32
      // ain't one of them.
      const SDValue &Target = Node->getOperand(1);
      assert(Target.getSimpleValueType() == llvm::MVT::i32);
      SDValue ZextTarget = CurDAG->getZExtOrTrunc(Target, dl, EVT(MVT::i64));
      SDValue Brind = CurDAG->getNode(ISD::BRIND, dl, MVT::Other,
                                      Node->getOperand(0), ZextTarget);
      ReplaceUses(SDValue(Node, 0), Brind);
      SelectCode(ZextTarget.getNode());
      SelectCode(Brind.getNode());
      return nullptr;
    }
    break;
  }

It leaves dead and invalid nodes behind.

H.J.