ARM cost model: Address computation in vector mem ops not free

Adds a function to target transform info to query for the cost of address
computation. The cost model analysis pass now also queries this interface.
The code in LoopVectorize adds the cost of address computation as part of the
memory instruction cost calculation. Only there, we know whether the instruction
will be scalarized or not.
Increase the penality for inserting in to D registers on swift. This becomes
necessary because we now always assume that address computation has a cost and
three is a closer value to the architecture.

radar://13097204

llvm-svn: 174713

1 files changed, 14 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 91d565976ad..f12b0bf0f39 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -3056,9 +3056,10 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
   // TODO: We need to estimate the cost of intrinsic calls.
   switch (I->getOpcode()) {
   case Instruction::GetElementPtr:
-    // We mark this instruction as zero-cost because scalar GEPs are usually
-    // lowered to the intruction addressing mode. At the moment we don't
-    // generate vector geps.
+    // We mark this instruction as zero-cost because the cost of GEPs in
+    // vectorized code depends on whether the corresponding memory instruction
+    // is scalarized or not. Therefore, we handle GEPs with the memory
+    // instruction cost.
     return 0;
   case Instruction::Br: {
     return TTI.getCFInstrCost(I->getOpcode());
@@ -3113,9 +3114,12 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
     unsigned AS = SI ? SI->getPointerAddressSpace() :
       LI->getPointerAddressSpace();
     Value *Ptr = SI ? SI->getPointerOperand() : LI->getPointerOperand();
-
+    // We add the cost of address computation here instead of with the gep
+    // instruction because only here we know whether the operation is
+    // scalarized.
     if (VF == 1)
-      return TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
+      return TTI.getAddressComputationCost(VectorTy) +
+        TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
 
     // Scalarized loads/stores.
     int Stride = Legal->isConsecutivePtr(Ptr);
@@ -3135,15 +3139,17 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
                                             VectorTy, i);
       }
 
-      // The cost of the scalar stores.
+      // The cost of the scalar loads/stores.
+      Cost += VF * TTI.getAddressComputationCost(ValTy->getScalarType());
       Cost += VF * TTI.getMemoryOpCost(I->getOpcode(), ValTy->getScalarType(),
                                        Alignment, AS);
       return Cost;
     }
 
     // Wide load/stores.
-    unsigned Cost = TTI.getMemoryOpCost(I->getOpcode(), VectorTy,
-                                        Alignment, AS);
+    unsigned Cost = TTI.getAddressComputationCost(VectorTy);
+    Cost += TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
+
     if (Reverse)
       Cost += TTI.getShuffleCost(TargetTransformInfo::SK_Reverse,
                                   VectorTy, 0);