zext / truncate is free on msp430. Inform codegen about this.

llvm-svn: 93556

lib/Target/MSP430/MSP430ISelLowering.cpp

@@ -967,6 +967,31 @@ const char *MSP430TargetLowering::getTargetNodeName(unsigned Opcode) const {
   }
 }
 
+bool MSP430TargetLowering::isTruncateFree(const Type *Ty1,
+                                          const Type *Ty2) const {
+  if (!Ty1->isInteger() || !Ty2->isInteger())
+    return false;
+
+  return (Ty1->getPrimitiveSizeInBits() > Ty2->getPrimitiveSizeInBits());
+}
+
+bool MSP430TargetLowering::isTruncateFree(EVT VT1, EVT VT2) const {
+  if (!VT1.isInteger() || !VT2.isInteger())
+    return false;
+
+  return (VT1.getSizeInBits() > VT2.getSizeInBits());
+}
+
+bool MSP430TargetLowering::isZExtFree(const Type *Ty1, const Type *Ty2) const {
+  // MSP430 implicitly zero-extends 8-bit results in 16-bit registers.
+  return 0 && Ty1->isInteger(8) && Ty2->isInteger(16);
+}
+
+bool MSP430TargetLowering::isZExtFree(EVT VT1, EVT VT2) const {
+  // MSP430 implicitly zero-extends 8-bit results in 16-bit registers.
+  return 0 && VT1 == MVT::i8 && VT2 == MVT::i16;
+}
+
 //===----------------------------------------------------------------------===//
 //  Other Lowering Code
 //===----------------------------------------------------------------------===//

lib/Target/MSP430/MSP430ISelLowering.h

@@ -99,6 +99,23 @@ namespace llvm {
     std::pair<unsigned, const TargetRegisterClass*>
     getRegForInlineAsmConstraint(const std::string &Constraint, EVT VT) const;
 
+    /// isTruncateFree - Return true if it's free to truncate a value of type
+    /// Ty1 to type Ty2. e.g. On msp430 it's free to truncate a i16 value in
+    /// register R15W to i8 by referencing its sub-register R15B.
+    virtual bool isTruncateFree(const Type *Ty1, const Type *Ty2) const;
+    virtual bool isTruncateFree(EVT VT1, EVT VT2) const;
+
+    /// isZExtFree - Return true if any actual instruction that defines a value
+    /// of type Ty1 implicit zero-extends the value to Ty2 in the result
+    /// register. This does not necessarily include registers defined in unknown
+    /// ways, such as incoming arguments, or copies from unknown virtual
+    /// registers. Also, if isTruncateFree(Ty2, Ty1) is true, this does not
+    /// necessarily apply to truncate instructions. e.g. on msp430, all
+    /// instructions that define 8-bit values implicit zero-extend the result
+    /// out to 16 bits.
+    virtual bool isZExtFree(const Type *Ty1, const Type *Ty2) const;
+    virtual bool isZExtFree(EVT VT1, EVT VT2) const;
+
     MachineBasicBlock* EmitInstrWithCustomInserter(MachineInstr *MI,
                                                    MachineBasicBlock *BB,
                     DenseMap<MachineBasicBlock*, MachineBasicBlock*> *EM) const;