Move CalculateRegClass to MRI::recomputeRegClass.

This function doesn't have anything to do with spill weights, and MRI
already has functions for manipulating the register class of a virtual
register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137123 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineRegisterInfo.cpp

@@ -14,7 +14,7 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Support/CommandLine.h"
+#include "llvm/Target/TargetMachine.h"
 using namespace llvm;
 
 MachineRegisterInfo::MachineRegisterInfo(const TargetRegisterInfo &TRI)
@@ -61,6 +61,37 @@ MachineRegisterInfo::constrainRegClass(unsigned Reg,
   return NewRC;
 }
 
+bool
+MachineRegisterInfo::recomputeRegClass(unsigned Reg, const TargetMachine &TM) {
+  const TargetInstrInfo *TII = TM.getInstrInfo();
+  const TargetRegisterInfo *TRI = TM.getRegisterInfo();
+  const TargetRegisterClass *OldRC = getRegClass(Reg);
+  const TargetRegisterClass *NewRC = TRI->getLargestLegalSuperClass(OldRC);
+
+  // Stop early if there is no room to grow.
+  if (NewRC == OldRC)
+    return false;
+
+  // Accumulate constraints from all uses.
+  for (reg_nodbg_iterator I = reg_nodbg_begin(Reg), E = reg_nodbg_end(); I != E;
+       ++I) {
+    // TRI doesn't have accurate enough information to model this yet.
+    if (I.getOperand().getSubReg())
+      return false;
+    // Inline asm instuctions don't remember their constraints.
+    if (I->isInlineAsm())
+      return false;
+    const TargetRegisterClass *OpRC =
+      TII->getRegClass(I->getDesc(), I.getOperandNo(), TRI);
+    if (OpRC)
+      NewRC = getCommonSubClass(NewRC, OpRC);
+    if (!NewRC || NewRC == OldRC)
+      return false;
+  }
+  setRegClass(Reg, NewRC);
+  return true;
+}
+
 /// createVirtualRegister - Create and return a new virtual register in the
 /// function with the specified register class.
 ///