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| ID | Project | Category | View Status | Date Submitted | Last Update | ||||
|---|---|---|---|---|---|---|---|---|---|
| 0000103 | mercury | Bug | public | 2009-09-14 12:17 | 2011-03-08 21:33 | ||||
| Reporter | wangp | ||||||||
| Assigned To | zs | ||||||||
| Priority | normal | Severity | minor | Reproducibility | always | ||||
| Status | resolved | Resolution | fixed | ||||||
| Product Version | |||||||||
| Target Version | Fixed in Version | ||||||||
| Summary | 0000103: bug in lcmc transformation | ||||||||
| Description | The compiler crashes on the given test case. % mmc --optimize-constructor-last-call lco_bug Uncaught Mercury exception: Software Error: map.lookup: key not found Key Type: term.var(parse_tree.prog_data.prog_var_type) Key Value: var(2) Value Type: ll_backend.var_locn.var_state | ||||||||
| Tags | No tags attached. | ||||||||
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zs (developer) 2011-03-08 21:33 |
If an argument in a recursive call is both a head variable AND is used in a unification that we are trying to move before the recursive call, like this: rec_call(..., HV2, X), HV3 = functor(HV2, X) then each call through this recursive call site is next to a unification that creates a cell with a field (in this case the first field) that needs to be set to the value of HV2 finally computed by a base case. After the Nth recursive call, there will be N cells. There is no way we can pass N addresses to the base case without making the transformed code pass a LIST of addresses in place of HV2 in the argument list. That would be a different transformation than what lco.m does, and it is far from clear that that transformation would be a good idea, since it doubles the number of loop iterations we would need to execute (N recursive calls, and N iterations of a loop to fill in the fields). The fix is to just disable the application of the lco transformation to this call. Fix committed 8 March 2011. |
| Notes |
| Issue History |
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| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2009-09-14 12:17 | wangp | New Issue | |
| 2009-09-14 12:17 | wangp | File Added: lco_bug.m | |
| 2009-09-14 12:18 | wangp | Status | new => assigned |
| 2009-09-14 12:18 | wangp | Assigned To | => zs |
| 2011-03-08 21:33 | zs | Note Added: 0000315 | |
| 2011-03-08 21:33 | zs | Status | assigned => resolved |
| 2011-03-08 21:33 | zs | Resolution | open => fixed |
| Issue History |