[AArch64] Consider widening instructions in cost calculations

The AArch64 instruction set has a few "widening" instructions (e.g., uaddl,
saddl, uaddw, etc.) that take one or more doubleword operands and produce
quadword results. The operands are automatically sign- or zero-extended as
appropriate. However, in LLVM IR, these extends are explicit. This patch
updates TTI to consider these widening instructions as single operations whose
cost is attached to the arithmetic instruction. It marks extends that are part
of a widening operation "free" and applies a sub-target specified overhead
(zero by default) to the arithmetic instructions.

Differential Revision: https://reviews.llvm.org/D32706

llvm-svn: 302582

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 99084444bdd..960019f41df 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -1819,11 +1819,13 @@ int BoUpSLP::getEntryCost(TreeEntry *E) {
           CInt->getValue().isPowerOf2())
         Op2VP = TargetTransformInfo::OP_PowerOf2;
 
-      int ScalarCost = VecTy->getNumElements() *
-                       TTI->getArithmeticInstrCost(Opcode, ScalarTy, Op1VK,
-                                                   Op2VK, Op1VP, Op2VP);
+      SmallVector<const Value *, 4> Operands(VL0->operand_values());
+      int ScalarCost =
+          VecTy->getNumElements() *
+          TTI->getArithmeticInstrCost(Opcode, ScalarTy, Op1VK, Op2VK, Op1VP,
+                                      Op2VP, Operands);
       int VecCost = TTI->getArithmeticInstrCost(Opcode, VecTy, Op1VK, Op2VK,
-                                                Op1VP, Op2VP);
+                                                Op1VP, Op2VP, Operands);
       return VecCost - ScalarCost;
     }
     case Instruction::GetElementPtr: {