[llvm] r220302 - [PBQP] Fix coalescing benefits

[David Blaikie]

On Tue, Oct 21, 2014 at 9:24 AM, Arnaud A. de Grandmaison <
arnaud.degrandmaison at arm.com> wrote:

> Author: aadg
> Date: Tue Oct 21 11:24:15 2014
> New Revision: 220302
>
> URL: http://llvm.org/viewvc/llvm-project?rev=220302&view=rev
> Log:
> [PBQP] Fix coalescing benefits
>
> As coalescing registers is a benefit, the cost should be improved (i.e.
> made smaller) when coalescing is possible.
>
> Modified:
>     llvm/trunk/lib/CodeGen/RegAllocPBQP.cpp
>
> Modified: llvm/trunk/lib/CodeGen/RegAllocPBQP.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegAllocPBQP.cpp?rev=220302&r1=220301&r2=220302&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/RegAllocPBQP.cpp (original)
> +++ llvm/trunk/lib/CodeGen/RegAllocPBQP.cpp Tue Oct 21 11:24:15 2014
> @@ -350,7 +350,7 @@ public:
>
>            if (PRegOpt < Allowed.size()) {
>              PBQPRAGraph::RawVector NewCosts(G.getNodeCosts(NId));
> -            NewCosts[PRegOpt + 1] += CBenefit;
> +            NewCosts[PRegOpt + 1] -= CBenefit;
>

Test coverage for this?


>              G.setNodeCosts(NId, std::move(NewCosts));
>            }
>          } else {
> @@ -395,7 +395,7 @@ private:
>        for (unsigned J = 0; J != Allowed2.size(); ++J) {
>          unsigned PReg2 = Allowed2[J];
>          if (PReg1 == PReg2)
> -          CostMat[I + 1][J + 1] += -Benefit;
> +          CostMat[I + 1][J + 1] -= Benefit;
>        }
>      }
>    }
>
>
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