[LLVMbugs] [Bug 16562] New: LegalizeTypes.cpp:618: void llvm::DAGTypeLegalizer::RemapValue(llvm::SDValue&): Assertion `N.getNode()->getNodeId() != NewNode && "Mapped to new node!"' failed.

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=16562

            Bug ID: 16562
           Summary: LegalizeTypes.cpp:618: void
                    llvm::DAGTypeLegalizer::RemapValue(llvm::SDValue&):
                    Assertion `N.getNode()->getNodeId() != NewNode &&
                    "Mapped to new node!"' failed.
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: hfinkel at anl.gov
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 10829
  --> http://llvm.org/bugs/attachment.cgi?id=10829&action=edit
bugpoint reduced test case

If you run the attached test case with:
llc -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7

then this crashes:
Scalarize node result 0: 0x123b0dc0: v1i64 = extract_subvector 0x12392bc0,
0x1239d790 [ORD=7] [ID=0]

Scalarize node operand 0: 0x123ad790: i64 = extract_vector_elt 0x123b0dc0,
0x123929c0 [ORD=7] [ID=0]

llc: /llvm-trunk/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp:618: void
llvm::DAGTypeLegalizer::RemapValue(llvm::SDValue&): Assertion
`N.getNode()->getNodeId() != NewNode && "Mapped to new node!"' failed.

This seems similar to http://llvm.org/bugs/show_bug.cgi?id=8923 (which Nadav
fixed a couple of years ago).

Also, this might just be a symptom of a more-general problem that I've noticed
before: we currently cannot replace a node with one of its operands.

(gdb) call Res.getNode()->dump()
0x123929c0: i64 = Constant<0> [ID=-3]

(gdb) call N->dump()
0x123ad790: i64 = extract_vector_elt 0x123b0dc0, 0x123929c0 [ORD=7] [ID=0]
(gdb) call N->getOperand(0).getNode()->dump()
0x123b0dc0: v1i64 = extract_subvector 0x12392bc0, 0x1239d790 [ORD=7] [ID=-3]
(gdb) call N->getOperand(1).getNode()->dump()
0x123929c0: i64 = Constant<0> [ID=-3]

(so the result is the constant 0 and so is one of the original operands)

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