[llvm] r220302 - [PBQP] Fix coalescing benefits

[Arnaud A. de Grandmaison]

This one was found by post-commit visual inspection --- I do not have any testcase handy. But I will see if I can come up with one.

 

Cheers,

Arnaud

 

From: David Blaikie [mailto:dblaikie at gmail.com] 
Sent: 21 October 2014 18:37
To: Arnaud De Grandmaison
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: [llvm] r220302 - [PBQP] Fix coalescing benefits

 

 

 

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 <http://llvm.org/viewvc/llvm-project?rev=220302&view=rev> &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 <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegAllocPBQP.cpp?rev=220302&r1=220301&r2=220302&view=diff> &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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