[llvm-bugs] [Bug 40294] New: DAGCombiner doesn't check legality for merging stores with noimplicitfloat

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=40294

            Bug ID: 40294
           Summary: DAGCombiner doesn't check legality for merging stores
                    with noimplicitfloat
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: nemanja.i.ibm at gmail.com
                CC: llvm-bugs at lists.llvm.org

This can be reproduced as follows:
$ cat a.ll 
define dso_local void @test(i64* nocapture %arr1) local_unnamed_addr #0 {
entry:
  %arrayidx = getelementptr inbounds i64, i64* %arr1, i64 2
  %0 = load i64, i64* %arrayidx, align 8
  store i64 %0, i64* %arr1, align 8
  %arrayidx2 = getelementptr inbounds i64, i64* %arr1, i64 3
  %1 = load i64, i64* %arrayidx2, align 8
  %arrayidx3 = getelementptr inbounds i64, i64* %arr1, i64 1
  store i64 %1, i64* %arrayidx3, align 8
  ret void
}

attributes #0 = { noimplicitfloat }

$ llc a.ll -mtriple=powerpc64le-unknown-unknown
llc:
/home/nemanjai/llvm/llvm-clean/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp:970:
void {anonymous}::SelectionDAGLegalize::LegalizeOp(llvm::SDNode*): Assertion
`(TLI.getTypeAction(*DAG.getContext(), Op.getValueType()) ==
TargetLowering::TypeLegal || TLI.isTypeLegal(Op.getValueType()) ||
Op.getOpcode() == ISD::TargetConstant || Op.getOpcode() == ISD::Register) &&
"Unexpected illegal type!"' failed.


The problem is that PPC does not override
TargetLowering::mergeStoresAfterLegalization() and the merging will produce an
i128 which isn't legal.
It will of course produce it prior to legalization as well, but the legalizer
will undo that, the problem is after legalization.

Note that without the noimplicitfloat attribute, things work because using
vectors is allowed and then it will find a corresponding vector type.

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