Provide AltOrders for specifying alternative allocation orders.

A register class can define AltOrders and AltOrderSelect instead of
defining method protos and bodies. The AltOrders lists can be defined
with set operations, and TableGen can verify that the alternative
allocation orders only contain valid registers.

This is currently an opt-in feature, and it is still possible to
override allocation_order_begin/end. That will not be true for long.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133320 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 3 deletions

diff --git a/utils/TableGen/CodeGenRegisters.h b/utils/TableGen/CodeGenRegisters.h
index 55f0b9b3aa..5e3d5e59c1 100644
--- a/utils/TableGen/CodeGenRegisters.h
+++ b/utils/TableGen/CodeGenRegisters.h
@@ -86,6 +86,7 @@ namespace llvm {
   class CodeGenRegisterClass {
     CodeGenRegister::Set Members;
     const std::vector<Record*> *Elements;
+    std::vector<SmallVector<Record*, 16> > AltOrders;
   public:
     Record *TheDef;
     std::string Namespace;
@@ -96,7 +97,7 @@ namespace llvm {
     bool Allocatable;
     // Map SubRegIndex -> RegisterClass
     DenseMap<Record*,Record*> SubRegClasses;
-    std::string MethodProtos, MethodBodies;
+    std::string MethodProtos, MethodBodies, AltOrderSelect;
 
     const std::string &getName() const;
     const std::vector<MVT::SimpleValueType> &getValueTypes() const {return VTs;}
@@ -125,10 +126,17 @@ namespace llvm {
 
     // Returns an ordered list of class members.
     // The order of registers is the same as in the .td file.
-    ArrayRef<Record*> getOrder() const {
-      return *Elements;
+    // No = 0 is the default allocation order, No = 1 is the first alternative.
+    ArrayRef<Record*> getOrder(unsigned No = 0) const {
+      if (No == 0)
+        return *Elements;
+      else
+        return AltOrders[No - 1];
     }
 
+    // Return the total number of allocation orders available.
+    unsigned getNumOrders() const { return 1 + AltOrders.size(); }
+
     CodeGenRegisterClass(CodeGenRegBank&, Record *R);
   };