[PATCH] D106351: [CostModel] Templatize EntryCost::Cost to allow custom cost metrics

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: sdesmalen, dmgreen, spatel, ABataev.
RKSimon requested review of this revision.
Herald added a project: LLVM.

We currently use an unsigned value for our CostTblEntry and TypeConversionCostTblEntry cost tables which is limiting depending on how the target wishes to handle various CostKinds etc.

For instance, targets might wish to store separate instruction count, latency or throughput values etc. On D46276 <https://reviews.llvm.org/D46276> we have been investigating storing a code snippet to improve latency/throughput cost calculations.

There is a slight problem in that template argument deduction was struggling to match the now templatized Costs[] tables in a ArrayRef constructor - I've added helper wrappers for CostTableLookup/ConvertCostTableLookup which avoids us having to update all existing calls with a template hint.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D106351

Files:
  llvm/include/llvm/CodeGen/CostTable.h


Index: llvm/include/llvm/CodeGen/CostTable.h
===================================================================
--- llvm/include/llvm/CodeGen/CostTable.h
+++ llvm/include/llvm/CodeGen/CostTable.h
@@ -21,15 +21,18 @@
 namespace llvm {
 
 /// Cost Table Entry
-struct CostTblEntry {
+template <typename CostKind>
+struct CostTblEntryT {
   int ISD;
   MVT::SimpleValueType Type;
-  unsigned Cost;
+  CostKind Cost;
 };
+using CostTblEntry = CostTblEntryT<unsigned>;
 
-/// Find in cost table, TypeTy must be comparable to CompareTy by ==
-inline const CostTblEntry *CostTableLookup(ArrayRef<CostTblEntry> Tbl,
-                                           int ISD, MVT Ty) {
+/// Find in cost table.
+template <class CostType>
+inline const CostTblEntryT<CostType> *
+CostTableLookup(ArrayRef<CostTblEntryT<CostType>> Tbl, int ISD, MVT Ty) {
   auto I = find_if(Tbl, [=](const CostTblEntry &Entry) {
     return ISD == Entry.ISD && Ty == Entry.Type;
   });
@@ -40,22 +43,33 @@
   return nullptr;
 }
 
+template <size_t N, class CostType>
+inline const CostTblEntry *
+CostTableLookup(const llvm::CostTblEntryT<CostType> (&Table)[N], int ISD,
+                MVT Ty) {
+  // Wrapper to fix template argument deduction failures.
+  return CostTableLookup<CostType>(
+      llvm::ArrayRef<llvm::CostTblEntryT<CostType>>(Table), ISD, Ty);
+}
+
 /// Type Conversion Cost Table
-struct TypeConversionCostTblEntry {
+template <typename CostKind> struct TypeConversionCostTblEntryT {
   int ISD;
   MVT::SimpleValueType Dst;
   MVT::SimpleValueType Src;
-  unsigned Cost;
+  CostKind Cost;
 };
+using TypeConversionCostTblEntry = TypeConversionCostTblEntryT<unsigned>;
 
-/// Find in type conversion cost table, TypeTy must be comparable to CompareTy
-/// by ==
-inline const TypeConversionCostTblEntry *
-ConvertCostTableLookup(ArrayRef<TypeConversionCostTblEntry> Tbl,
+/// Find in type conversion cost table.
+template <class CostType>
+inline const TypeConversionCostTblEntryT<CostType> *
+ConvertCostTableLookup(ArrayRef<TypeConversionCostTblEntryT<CostType>> Tbl,
                        int ISD, MVT Dst, MVT Src) {
-  auto I = find_if(Tbl, [=](const TypeConversionCostTblEntry &Entry) {
-    return ISD == Entry.ISD && Src == Entry.Src && Dst == Entry.Dst;
-  });
+  auto I =
+      find_if(Tbl, [=](const TypeConversionCostTblEntryT<CostType> &Entry) {
+        return ISD == Entry.ISD && Src == Entry.Src && Dst == Entry.Dst;
+      });
   if (I != Tbl.end())
     return I;
 
@@ -63,6 +77,16 @@
   return nullptr;
 }
 
+template <size_t N, class CostType>
+inline const TypeConversionCostTblEntryT<CostType> *ConvertCostTableLookup(
+    const llvm::TypeConversionCostTblEntryT<CostType> (&Table)[N], int ISD,
+    MVT Dst, MVT Src) {
+  // Wrapper to fix template argument deduction failures.
+  return ConvertCostTableLookup<CostType>(
+      llvm::ArrayRef<TypeConversionCostTblEntryT<CostType>>(Table), ISD, Dst,
+      Src);
+}
+
 } // namespace llvm
 
 #endif /* LLVM_CODEGEN_COSTTABLE_H_ */


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