R600/SI: Allow partial unrolling and increase thresholds.

[arsenm]

Summary

Doubling the base unroll threshold is a conservative increase, and might want to be increased more later.

[arsenm]

r213985

lib/Target/R600/AMDGPUTargetTransformInfo.cpp

 
 void AMDGPUTTI::getUnrollingPreferences(Loop *L,
                                         UnrollingPreferences &UP) const {
+  UP.Threshold = 300; // Twice the default.
+  UP.Count = UINT_MAX;
+  UP.Partial = true;
+
+  // TODO: Do we want runtime unrolling?
+
   for (const BasicBlock *BB : L->getBlocks()) {
     for (const Instruction &I : *BB) {
       const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&I);

         //
         // Don't use the maximum allowed value here as it will make some
         // programs way too big.
-        UP.Threshold = 500;
+        UP.Threshold = 800;
       }
     }
   }