Encode register class constreaints in inline asm instructions.

The inline asm operand constraint is initially encoded in the virtual
register for the operand, but that register class may change during
coalescing, and the original constraint is lost.

Encode the original register class as part of the flag word for each
inline asm operand.  This makes it possible to recover the actual
constraint required by inline asm, just like we can for normal
instructions.

llvm-svn: 141833

include/llvm/InlineAsm.h

@@ -219,6 +219,7 @@ public:
   
   static unsigned getFlagWord(unsigned Kind, unsigned NumOps) {
     assert(((NumOps << 3) & ~0xffff) == 0 && "Too many inline asm operands!");
+    assert(Kind >= Kind_RegUse && Kind <= Kind_Mem && "Invalid Kind");
     return Kind | (NumOps << 3);
   }
   
@@ -227,9 +228,24 @@ public:
   /// to a previous output operand.
   static unsigned getFlagWordForMatchingOp(unsigned InputFlag,
                                            unsigned MatchedOperandNo) {
+    assert(MatchedOperandNo <= 0x7fff && "Too big matched operand");
+    assert((InputFlag & ~0xffff) == 0 && "High bits already contain data");
     return InputFlag | Flag_MatchingOperand | (MatchedOperandNo << 16);
   }
 
+  /// getFlagWordForRegClass - Augment an existing flag word returned by
+  /// getFlagWord with the required register class for the following register
+  /// operands.
+  /// A tied use operand cannot have a register class, use the register class
+  /// from the def operand instead.
+  static unsigned getFlagWordForRegClass(unsigned InputFlag, unsigned RC) {
+    // Store RC + 1, reserve the value 0 to mean 'no register class'.
+    ++RC;
+    assert(RC <= 0x7fff && "Too large register class ID");
+    assert((InputFlag & ~0xffff) == 0 && "High bits already contain data");
+    return InputFlag | (RC << 16);
+  }
+
   static unsigned getKind(unsigned Flags) {
     return Flags & 7;
   }
@@ -259,6 +275,19 @@ public:
     return true;
   }
 
+  /// hasRegClassConstraint - Returns true if the flag contains a register
+  /// class constraint.  Sets RC to the register class ID.
+  static bool hasRegClassConstraint(unsigned Flag, unsigned &RC) {
+    if (Flag & Flag_MatchingOperand)
+      return false;
+    unsigned High = Flag >> 16;
+    // getFlagWordForRegClass() uses 0 to mean no register class, and otherwise
+    // stores RC + 1.
+    if (!High)
+      return false;
+    RC = High - 1;
+    return true;
+  }
 
 };
 

lib/CodeGen/MachineInstr.cpp

@@ -1422,18 +1422,27 @@ void MachineInstr::print(raw_ostream &OS, const TargetMachine *TM) const {
       OS << '$' << AsmOpCount++;
       unsigned Flag = MO.getImm();
       switch (InlineAsm::getKind(Flag)) {
-      case InlineAsm::Kind_RegUse:             OS << ":[reguse]"; break;
-      case InlineAsm::Kind_RegDef:             OS << ":[regdef]"; break;
-      case InlineAsm::Kind_RegDefEarlyClobber: OS << ":[regdef-ec]"; break;
-      case InlineAsm::Kind_Clobber:            OS << ":[clobber]"; break;
-      case InlineAsm::Kind_Imm:                OS << ":[imm]"; break;
-      case InlineAsm::Kind_Mem:                OS << ":[mem]"; break;
-      default: OS << ":[??" << InlineAsm::getKind(Flag) << ']'; break;
+      case InlineAsm::Kind_RegUse:             OS << ":[reguse"; break;
+      case InlineAsm::Kind_RegDef:             OS << ":[regdef"; break;
+      case InlineAsm::Kind_RegDefEarlyClobber: OS << ":[regdef-ec"; break;
+      case InlineAsm::Kind_Clobber:            OS << ":[clobber"; break;
+      case InlineAsm::Kind_Imm:                OS << ":[imm"; break;
+      case InlineAsm::Kind_Mem:                OS << ":[mem"; break;
+      default: OS << ":[??" << InlineAsm::getKind(Flag); break;
       }
 
+      unsigned RCID = 0;
+      if (InlineAsm::hasRegClassConstraint(Flag, RCID))
+        if (TM)
+          OS << ':' << TM->getRegisterInfo()->getRegClass(RCID)->getName();
+        else
+          OS << ":RC" << RCID;
+
       unsigned TiedTo = 0;
       if (InlineAsm::isUseOperandTiedToDef(Flag, TiedTo))
-        OS << " [tiedto:$" << TiedTo << ']';
+        OS << " tiedto:$" << TiedTo;
+
+      OS << ']';
 
       // Compute the index of the next operand descriptor.
       AsmDescOp += 1 + InlineAsm::getNumOperandRegisters(Flag);

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -788,6 +788,18 @@ void RegsForValue::AddInlineAsmOperands(unsigned Code, bool HasMatching,
   unsigned Flag = InlineAsm::getFlagWord(Code, Regs.size());
   if (HasMatching)
     Flag = InlineAsm::getFlagWordForMatchingOp(Flag, MatchingIdx);
+  else if (!Regs.empty() &&
+           TargetRegisterInfo::isVirtualRegister(Regs.front())) {
+    // Put the register class of the virtual registers in the flag word.  That
+    // way, later passes can recompute register class constraints for inline
+    // assembly as well as normal instructions.
+    // Don't do this for tied operands that can use the regclass information
+    // from the def.
+    const MachineRegisterInfo &MRI = DAG.getMachineFunction().getRegInfo();
+    const TargetRegisterClass *RC = MRI.getRegClass(Regs.front());
+    Flag = InlineAsm::getFlagWordForRegClass(Flag, RC->getID());
+  }
+
   SDValue Res = DAG.getTargetConstant(Flag, MVT::i32);
   Ops.push_back(Res);