CostModel: Add parameter to instruction cost to further classify operand values

On certain architectures we can support efficient vectorized version of
instructions if the operand value is uniform (splat) or a constant scalar.
An example of this is a vector shift on x86.

We can efficiently support

for (i = 0 ; i < ; i += 4)
  w[0:3] = v[0:3] << <2, 2, 2, 2>

but not

for (i = 0; i < ; i += 4)
  w[0:3] = v[0:3] << x[0:3]

This patch adds a parameter to getArithmeticInstrCost to further qualify operand
values as uniform or uniform constant.

Targets can then choose to return a different cost for instructions with such
operand values.

A follow-up commit will test this feature on x86.

radar://13576547

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178807 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 1 deletions

diff --git a/include/llvm/Analysis/TargetTransformInfo.h b/include/llvm/Analysis/TargetTransformInfo.h
index ccab19495f..a9d6725d86 100644
--- a/include/llvm/Analysis/TargetTransformInfo.h
+++ b/include/llvm/Analysis/TargetTransformInfo.h
@@ -263,6 +263,13 @@ public:
     SK_ExtractSubvector ///< ExtractSubvector Index indicates start offset.
   };
 
+  /// \brief Additonal information about an operand's possible values.
+  enum OperandValueKind {
+    OK_AnyValue,            // Operand can have any value.
+    OK_UniformValue,        // Operand is uniform (splat of a value).
+    OK_UniformConstantValue // Operand is uniform constant.
+  };
+
   /// \return The number of scalar or vector registers that the target has.
   /// If 'Vectors' is true, it returns the number of vector registers. If it is
   /// set to false, it returns the number of scalar registers.
@@ -277,7 +284,9 @@ public:
   virtual unsigned getMaximumUnrollFactor() const;
 
   /// \return The expected cost of arithmetic ops, such as mul, xor, fsub, etc.
-  virtual unsigned getArithmeticInstrCost(unsigned Opcode, Type *Ty) const;
+  virtual unsigned getArithmeticInstrCost(unsigned Opcode, Type *Ty,
+                                  OperandValueKind Opd1Info = OK_AnyValue,
+                                  OperandValueKind Opd2Info = OK_AnyValue) const;
 
   /// \return The cost of a shuffle instruction of kind Kind and of type Tp.
   /// The index and subtype parameters are used by the subvector insertion and