+/// getConstraintGenerality - Return an integer indicating how general CT is.
+static unsigned getConstraintGenerality(TargetLowering::ConstraintType CT) {
+ switch (CT) {
+ default: assert(0 && "Unknown constraint type!");
+ case TargetLowering::C_Other:
+ case TargetLowering::C_Unknown:
+ return 0;
+ case TargetLowering::C_Register:
+ return 1;
+ case TargetLowering::C_RegisterClass:
+ return 2;
+ case TargetLowering::C_Memory:
+ return 3;
+ }
+}
+
+void AsmOperandInfo::ComputeConstraintToUse(const TargetLowering &TLI) {
+ assert(!Codes.empty() && "Must have at least one constraint");
+
+ std::string *Current = &Codes[0];
+ TargetLowering::ConstraintType CurType = TLI.getConstraintType(*Current);
+ if (Codes.size() == 1) { // Single-letter constraints ('r') are very common.
+ ConstraintCode = *Current;
+ ConstraintType = CurType;
+ return;
+ }
+
+ unsigned CurGenerality = getConstraintGenerality(CurType);
+
+ // If we have multiple constraints, try to pick the most general one ahead
+ // of time. This isn't a wonderful solution, but handles common cases.
+ for (unsigned j = 1, e = Codes.size(); j != e; ++j) {
+ TargetLowering::ConstraintType ThisType = TLI.getConstraintType(Codes[j]);
+ unsigned ThisGenerality = getConstraintGenerality(ThisType);
+ if (ThisGenerality > CurGenerality) {
+ // This constraint letter is more general than the previous one,
+ // use it.
+ CurType = ThisType;
+ Current = &Codes[j];
+ CurGenerality = ThisGenerality;
+ }
+ }
+
+ ConstraintCode = *Current;
+ ConstraintType = CurType;
+}
+
+