[LLVMugs][Bug 20122] Patch ready
wuhui1973
wuhui1973 at 163.com
Tue Jul 1 02:57:06 PDT 2014
Hello Hal:
I found this comment about the assertion:
// In theory, this is combinatorial. In practice, it needs to be bounded
// by a small number of sets for regpressure to be efficient.
// If the assert is hit, we need to implement pruning.
assert(Idx < (2*NumRegUnitSubSets) && "runaway unit set inference");
Seems the author had forseen this problem, and he (she) suggested to prune the unitset.
I try to prune the unitset by pruneUnitSets if it exceeds the limit, but not succeed - the set is not reduced.
I am now trying to open the debug output available in the code and see what's happening.
Just a question: How to enable DEBUG macro in this source, which is run by tablegen?
However, this error can be avoid, just using assert(Idx < (3*NumRegUnitSubSets) && "runaway unit set inference");
Regards & Thanks
At 2014-07-01 05:42:20, "Hal Finkel" <hfinkel at anl.gov> wrote:
>Hi,
>
>With this patch applied, building LLVM's AMDGPU target fails:
>
>/src/llvm-trunk/utils/TableGen/CodeGenRegisters.cpp:1588: void llvm::CodeGenRegBank::computeRegUnitSets(): Assertion `Idx < (2*NumRegUnitSubSets) && "runaway unit set inference"' failed.
>
>Maybe the threshold in the assert just needs to be loosened, but we'd need to understand what is going on here.
>
> -Hal
>
>----- Original Message -----
>> From: "wuhui1973" <wuhui1973 at 163.com>
>> To: llvm-commits at cs.uiuc.edu
>> Sent: Sunday, June 29, 2014 11:08:40 PM
>> Subject: [LLVMugs][Bug 20122] Patch ready
>>
>>
>>
>>
>>
>> [ reply ] [-] Description hui wu 2014-06-24 21:35:52 CDT In function
>> CodeGenRegBank::computeRegUnitSets, below code fragment is used to
>> calculate the transitive closure of set union of intersecting sets.
>>
>> // Iterate over all unit sets, including new ones added by this
>> loop.
>> unsigned NumRegUnitSubSets = RegUnitSets.size();
>> for (unsigned Idx = 0, EndIdx = RegUnitSets.size(); Idx != EndIdx;
>> ++Idx) {
>> // In theory, this is combinatorial. In practice, it needs to be
>> bounded
>> // by a small number of sets for regpressure to be efficient.
>> // If the assert is hit, we need to implement pruning.
>> assert(Idx < (2*NumRegUnitSubSets) && "runaway unit set
>> inference");
>>
>> // Compare new sets with all original classes.
>> for (unsigned SearchIdx = (Idx >= NumRegUnitSubSets) ? 0 : Idx+1;
>> SearchIdx != EndIdx; ++SearchIdx) {
>> std::set<unsigned> Intersection;
>> std::set_intersection(RegUnitSets[Idx].Units.begin(),
>> RegUnitSets[Idx].Units.end(),
>> RegUnitSets[SearchIdx].Units.begin(),
>> RegUnitSets[SearchIdx].Units.end(),
>> std::inserter(Intersection,
>> Intersection.begin()));
>> if (Intersection.empty())
>> continue;
>>
>> // Speculatively grow the RegUnitSets to hold the new set.
>> RegUnitSets.resize(RegUnitSets.size() + 1);
>> RegUnitSets.back().Name =
>> RegUnitSets[Idx].Name + "+" + RegUnitSets[SearchIdx].Name;
>>
>> std::set_union(RegUnitSets[Idx].Units.begin(),
>> RegUnitSets[Idx].Units.end(),
>> RegUnitSets[SearchIdx].Units.begin(),
>> RegUnitSets[SearchIdx].Units.end(),
>> std::inserter(RegUnitSets.back().Units,
>> RegUnitSets.back().Units.begin()));
>>
>> // Find an existing RegUnitSet, or add the union to the unique
>> sets.
>> std::vector<RegUnitSet>::const_iterator SetI =
>> findRegUnitSet(RegUnitSets, RegUnitSets.back());
>> if (SetI != llvm::prior(RegUnitSets.end()))
>> RegUnitSets.pop_back();
>> }
>> }
>>
>> However, the use of EndIdx like that is not correct, it makes the for
>> loop exiting too early without handling the new added sets. The
>> correct way should be:
>>
>> // Iterate over all unit sets, including new ones added by this
>> loop.
>> unsigned NumRegUnitSubSets = RegUnitSets.size();
>> for (unsigned Idx = 0; Idx != RegUnitSets.size(); ++Idx) {
>> // In theory, this is combinatorial. In practice, it needs to be
>> bounded
>> // by a small number of sets for regpressure to be efficient.
>> // If the assert is hit, we need to implement pruning.
>> assert(Idx < (2*NumRegUnitSubSets) && "runaway unit set
>> inference");
>>
>> // Compare new sets with all original classes.
>> for (unsigned SearchIdx = (Idx >= NumRegUnitSubSets) ? 0 : Idx+1;
>> SearchIdx != RegUnitSets.size(); ++SearchIdx) {
>> std::set<unsigned> Intersection;
>> std::set_intersection(RegUnitSets[Idx].Units.begin(),
>> RegUnitSets[Idx].Units.end(),
>> RegUnitSets[SearchIdx].Units.begin(),
>> RegUnitSets[SearchIdx].Units.end(),
>> std::inserter(Intersection,
>> Intersection.begin()));
>> if (Intersection.empty())
>> continue;
>>
>> // Speculatively grow the RegUnitSets to hold the new set.
>> RegUnitSets.resize(RegUnitSets.size() + 1);
>> RegUnitSets.back().Name =
>> RegUnitSets[Idx].Name + "+" + RegUnitSets[SearchIdx].Name;
>>
>> std::set_union(RegUnitSets[Idx].Units.begin(),
>> RegUnitSets[Idx].Units.end(),
>> RegUnitSets[SearchIdx].Units.begin(),
>> RegUnitSets[SearchIdx].Units.end(),
>> std::inserter(RegUnitSets.back().Units,
>> RegUnitSets.back().Units.begin()));
>>
>> // Find an existing RegUnitSet, or add the union to the unique
>> sets.
>> std::vector<RegUnitSet>::const_iterator SetI =
>> findRegUnitSet(RegUnitSets, RegUnitSets.back());
>> if (SetI != llvm::prior(RegUnitSets.end()))
>> RegUnitSets.pop_ back();
>> }
>> }
>>
>> [ reply ] [-] Comment 1 Hal Finkel 2014-06-25 05:02:27 CDT Thanks for
>> filing this bug; do you know if this is still a problem in llvm
>> trunk? If so, the best way to provide this fix is to send a patch to
>> the llvm-commits mailing list. That is how we normally review
>> proposed patches.
>> http://llvm.org/docs/DeveloperPolicy.html#making-and-submitting-a-patch
>> Also, if you know how to generate a test that triggers the incorrect
>> behavior, that would be great!
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>
>
>--
>Hal Finkel
>Assistant Computational Scientist
>Leadership Computing Facility
>Argonne National Laboratory
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