CMM compiles with 8.0.2, fails with git HEAD

I'm trying to implement Float <-> Word32 bit casts (Double <-> Word64 works fine) in CMM using:

stg_word32ToFloatzh(I32 w)
{
    F_ f;
    P_ ptr;

    STK_CHK_GEN_N (FLOAT_STACK_WDS);

    reserve FLOAT_STACK_WDS = ptr {
        I32[ptr] = w;
        f = F_[ptr];
    }

    return (f);
}

stg_floatToWord32zh(F_ f)
{
    I32 w;
    P_ ptr;

    STK_CHK_GEN_N (FLOAT_STACK_WDS);

    reserve FLOAT_STACK_WDS = ptr {
        I32[ptr] = f;
        w = I32[ptr];
    }

    return (w);
}

This compiles correctly and passes all tests with ghc 8.0.2, but compiling the above CMM with git HEAD (currently 1e58efb1) results in:

Cmm lint error:
  in basic block cq
    in assignment: 
      _cj::I32 = R1;
      Reg ty: I32
      Rhs ty: I64
Program was:
  {offset
    cq: // global
        _cj::I32 = R1;
        //tick src<rts/CastFloatWord.cmm:(49,1)-(61,1)>
        goto cm;
    cm: // global
        if ((old + 0) - 8 / 8 < SpLim) (likely: False) goto co; else goto cp;
    co: // global
        I64[(young<cn> + 8)] = cn;
        call stg_gc_noregs() returns to cn, args: 8, res: 8, upd: 8;
    cn: // global
        goto cm;
    cp: // global
        _cl::P64 = (old + 16);
        //tick src<rts/CastFloatWord.cmm:(55,29)-(58,5)>
        I32[_cl::P64] = _cj::I32;
        _ck::F32 = F32[_cl::P64];
        F1 = _ck::F32;
        call (P64[(old + 8)])(F1) args: 8, res: 0, upd: 8;
  }

ghc 8.0.2 is accepts this code and gives the correct results, so I can only assume that git HEAD is incorrect.

Trac metadata

Trac field	Value
Version	8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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