Adding simple cast cost to ARM

Changing ARMBaseTargetMachine to return ARMTargetLowering intead of
the generic one (similar to x86 code).

Tests showing which instructions were added to cast when necessary
or cost zero when not. Downcast to 16 bits are not lowered in NEON,
so costs are not there yet.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173849 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 42 insertions, 2 deletions

diff --git a/lib/Target/ARM/ARMTargetTransformInfo.cpp b/lib/Target/ARM/ARMTargetTransformInfo.cpp
index 404a6fff11..61cb1f6b9a 100644
--- a/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -20,6 +20,7 @@
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/CostTable.h"
 using namespace llvm;
 
 // Declare the pass initialization routine locally as target-specific passes
@@ -34,18 +35,20 @@ namespace {
 class ARMTTI : public ImmutablePass, public TargetTransformInfo {
   const ARMBaseTargetMachine *TM;
   const ARMSubtarget *ST;
+  const ARMTargetLowering *TLI;
 
   /// Estimate the overhead of scalarizing an instruction. Insert and Extract
   /// are set if the result needs to be inserted and/or extracted from vectors.
   unsigned getScalarizationOverhead(Type *Ty, bool Insert, bool Extract) const;
 
 public:
-  ARMTTI() : ImmutablePass(ID), TM(0), ST(0) {
+  ARMTTI() : ImmutablePass(ID), TM(0), ST(0), TLI(0) {
     llvm_unreachable("This pass cannot be directly constructed");
   }
 
   ARMTTI(const ARMBaseTargetMachine *TM)
-      : ImmutablePass(ID), TM(TM), ST(TM->getSubtargetImpl()) {
+      : ImmutablePass(ID), TM(TM), ST(TM->getSubtargetImpl()),
+        TLI(TM->getTargetLowering()) {
     initializeARMTTIPass(*PassRegistry::getPassRegistry());
   }
 
@@ -111,6 +114,9 @@ public:
     return 1;
   }
 
+  unsigned getCastInstrCost(unsigned Opcode, Type *Dst,
+                                      Type *Src) const;
+
   /// @}
 };
 
@@ -157,3 +163,37 @@ unsigned ARMTTI::getIntImmCost(const APInt &Imm, Type *Ty) const {
   }
   return 2;
 }
+
+unsigned ARMTTI::getCastInstrCost(unsigned Opcode, Type *Dst,
+                                    Type *Src) const {
+  int ISD = TLI->InstructionOpcodeToISD(Opcode);
+  assert(ISD && "Invalid opcode");
+
+  EVT SrcTy = TLI->getValueType(Src);
+  EVT DstTy = TLI->getValueType(Dst);
+
+  if (!SrcTy.isSimple() || !DstTy.isSimple())
+    return TargetTransformInfo::getCastInstrCost(Opcode, Dst, Src);
+
+  // Some arithmetic, load and store operations have specific instructions
+  // to cast up/down their types automatically at no extra cost
+  // TODO: Get these tables to know at least what the related operations are
+  static const TypeConversionCostTblEntry<MVT> NEONConversionTbl[] = {
+    { ISD::SIGN_EXTEND, MVT::v4i32, MVT::v4i16, 0 },
+    { ISD::ZERO_EXTEND, MVT::v4i32, MVT::v4i16, 0 },
+    { ISD::SIGN_EXTEND, MVT::v2i64, MVT::v2i32, 1 },
+    { ISD::ZERO_EXTEND, MVT::v2i64, MVT::v2i32, 1 },
+    { ISD::TRUNCATE,    MVT::v4i32, MVT::v4i64, 0 },
+    { ISD::TRUNCATE,    MVT::v4i16, MVT::v4i32, 1 },
+  };
+
+  if (ST->hasNEON()) {
+    int Idx = ConvertCostTableLookup<MVT>(NEONConversionTbl,
+                                array_lengthof(NEONConversionTbl),
+                                ISD, DstTy.getSimpleVT(), SrcTy.getSimpleVT());
+    if (Idx != -1)
+      return NEONConversionTbl[Idx].Cost;
+  }
+
+  return TargetTransformInfo::getCastInstrCost(Opcode, Dst, Src);
+}