[TLI] Add a new hook to TargetLowering to query the target if a load of a constant should be converted to simply the constant itself.

Before this patch we used getIntImmCost from TargetTransformInfo to determine if
a load of a constant should be converted to just a constant, but the threshold
for this was set to an arbitrary value. This value works well for the two
targets (X86 and ARM) that implement this target-hook, but it isn't
target-independent at all.

Now targets have the possibility to decide directly if this optimization should
be performed. The default value is set to false to preserve the current
behavior. The target hook has been moved to TargetLowering, which removed the
last use and need of TargetTransformInfo in SelectionDAG.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200271 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 10 insertions, 8 deletions

diff --git a/include/llvm/Analysis/TargetTransformInfo.h b/include/llvm/Analysis/TargetTransformInfo.h
index f2613e35c5..ec3e606544 100644
--- a/include/llvm/Analysis/TargetTransformInfo.h
+++ b/include/llvm/Analysis/TargetTransformInfo.h
@@ -92,7 +92,6 @@ public:
   enum TargetCostConstants {
     TCC_Free = 0,       ///< Expected to fold away in lowering.
     TCC_Basic = 1,      ///< The cost of a typical 'add' instruction.
-    TCC_Load = 3,
     TCC_Expensive = 4   ///< The cost of a 'div' instruction on x86.
   };
 
diff --git a/include/llvm/CodeGen/SelectionDAG.h b/include/llvm/CodeGen/SelectionDAG.h
index 523c81337c..e3aed4d93b 100644
--- a/include/llvm/CodeGen/SelectionDAG.h
+++ b/include/llvm/CodeGen/SelectionDAG.h
@@ -36,7 +36,6 @@ class MDNode;
 class SDDbgValue;
 class TargetLowering;
 class TargetSelectionDAGInfo;
-class TargetTransformInfo;
 
 class SDVTListNode : public FoldingSetNode {
   friend struct FoldingSetTrait<SDVTListNode>;
@@ -169,7 +168,6 @@ void checkForCycles(const SelectionDAG *DAG);
 class SelectionDAG {
   const TargetMachine &TM;
   const TargetSelectionDAGInfo &TSI;
-  const TargetTransformInfo *TTI;
   const TargetLowering *TLI;
   MachineFunction *MF;
   LLVMContext *Context;
@@ -269,8 +267,7 @@ public:
   /// init - Prepare this SelectionDAG to process code in the given
   /// MachineFunction.
   ///
-  void init(MachineFunction &mf, const TargetTransformInfo *TTI,
-            const TargetLowering *TLI);
+  void init(MachineFunction &mf, const TargetLowering *TLI);
 
   /// clear - Clear state and free memory necessary to make this
   /// SelectionDAG ready to process a new block.
@@ -281,7 +278,6 @@ public:
   const TargetMachine &getTarget() const { return TM; }
   const TargetLowering &getTargetLoweringInfo() const { return *TLI; }
   const TargetSelectionDAGInfo &getSelectionDAGInfo() const { return TSI; }
-  const TargetTransformInfo *getTargetTransformInfo() const { return TTI; }
   LLVMContext *getContext() const {return Context; }
 
   /// viewGraph - Pop up a GraphViz/gv window with the DAG rendered using 'dot'.
diff --git a/include/llvm/CodeGen/SelectionDAGISel.h b/include/llvm/CodeGen/SelectionDAGISel.h
index b5ec8cb075..5f1c636dc6 100644
--- a/include/llvm/CodeGen/SelectionDAGISel.h
+++ b/include/llvm/CodeGen/SelectionDAGISel.h
@@ -30,7 +30,6 @@ namespace llvm {
   class MachineInstr;
   class TargetLowering;
   class TargetLibraryInfo;
-  class TargetTransformInfo;
   class FunctionLoweringInfo;
   class ScheduleHazardRecognizer;
   class GCFunctionInfo;
@@ -43,7 +42,6 @@ class SelectionDAGISel : public MachineFunctionPass {
 public:
   TargetMachine &TM;
   const TargetLibraryInfo *LibInfo;
-  const TargetTransformInfo *TTI;
   FunctionLoweringInfo *FuncInfo;
   MachineFunction *MF;
   MachineRegisterInfo *RegInfo;
diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index c8351b7c5e..e9d87291aa 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -1287,6 +1287,15 @@ public:
     return false;
   }
 
+  /// \brief Return true if it is beneficial to convert a load of a constant to
+  /// just the constant itself.
+  /// On some targets it might be more efficient to use a combination of
+  /// arithmetic instructions to materialize the constant instead of loading it
+  /// from a constant pool.
+  virtual bool shouldConvertConstantLoadToIntImm(const APInt &Imm,
+                                                 Type *Ty) const {
+    return false;
+  }
   //===--------------------------------------------------------------------===//
   // Runtime Library hooks
   //