2 files changed, 46 insertions, 0 deletions
diff --git a/include/llvm/CodeGen/MachineInstr.h b/include/llvm/CodeGen/MachineInstr.h
index a6376bee4e..cae38f3470 100644
--- a/include/llvm/CodeGen/MachineInstr.h
+++ b/include/llvm/CodeGen/MachineInstr.h
@@ -32,6 +32,7 @@ namespace llvm {
 template <typename T> class SmallVectorImpl;
 class AliasAnalysis;
 class TargetInstrInfo;
+class TargetRegisterClass;
 class TargetRegisterInfo;
 class MachineFunction;
 class MachineMemOperand;
@@ -400,6 +401,18 @@ public:
   ///
   int findInlineAsmFlagIdx(unsigned OpIdx, unsigned *GroupNo = 0) const;
 
+  /// getRegClassConstraint - Compute the static register class constraint for
+  /// operand OpIdx.  For normal instructions, this is derived from the
+  /// MCInstrDesc.  For inline assembly it is derived from the flag words.
+  ///
+  /// Returns NULL if the static register classs constraint cannot be
+  /// determined.
+  ///
+  const TargetRegisterClass*
+  getRegClassConstraint(unsigned OpIdx,
+                        const TargetInstrInfo *TII,
+                        const TargetRegisterInfo *TRI) const;
+
   /// isRegTiedToUseOperand - Given the index of a register def operand,
   /// check if the register def is tied to a source operand, due to either
   /// two-address elimination or inline assembly constraints. Returns the
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index 965c6c5bca..0ef1ef603b 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -854,6 +854,39 @@ int MachineInstr::findInlineAsmFlagIdx(unsigned OpIdx,
   return -1;
 }
 
+const TargetRegisterClass*
+MachineInstr::getRegClassConstraint(unsigned OpIdx,
+                                    const TargetInstrInfo *TII,
+                                    const TargetRegisterInfo *TRI) const {
+  // Most opcodes have fixed constraints in their MCInstrDesc.
+  if (!isInlineAsm())
+    return TII->getRegClass(getDesc(), OpIdx, TRI);
+
+  if (!getOperand(OpIdx).isReg())
+    return NULL;
+
+  // For tied uses on inline asm, get the constraint from the def.
+  unsigned DefIdx;
+  if (getOperand(OpIdx).isUse() && isRegTiedToDefOperand(OpIdx, &DefIdx))
+    OpIdx = DefIdx;
+
+  // Inline asm stores register class constraints in the flag word.
+  int FlagIdx = findInlineAsmFlagIdx(OpIdx);
+  if (FlagIdx < 0)
+    return NULL;
+
+  unsigned Flag = getOperand(FlagIdx).getImm();
+  unsigned RCID;
+  if (InlineAsm::hasRegClassConstraint(Flag, RCID))
+    return TRI->getRegClass(RCID);
+
+  // Assume that all registers in a memory operand are pointers.
+  if (InlineAsm::getKind(Flag) == InlineAsm::Kind_Mem)
+    return TRI->getPointerRegClass();
+
+  return NULL;
+}
+
 /// findRegisterUseOperandIdx() - Returns the MachineOperand that is a use of
 /// the specific register or -1 if it is not found. It further tightens
 /// the search criteria to a use that kills the register if isKill is true.