Add TRI::getSubClassWithSubReg(RC, Idx) function.

This function is used to constrain a register class to a sub-class that
supports the given sub-register index.

For example, getSubClassWithSubReg(GR32, sub_8bit) -> GR32_ABCD.

The function will be used to compute register classes when emitting
INSERT_SUBREG and EXTRACT_SUBREG nodes and for register class inflation
of sub-register operations.

The version provided by TableGen is usually adequate, but targets can
override.

llvm-svn: 141142

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/utils/TableGen/CodeGenRegisters.h b/llvm/utils/TableGen/CodeGenRegisters.h
index 72c8ac05025..ab3e68efc24 100644
--- a/llvm/utils/TableGen/CodeGenRegisters.h
+++ b/llvm/utils/TableGen/CodeGenRegisters.h
@@ -101,6 +101,9 @@ namespace llvm {
     // super-class.
     void inheritProperties(CodeGenRegBank&);
 
+    // Map SubRegIndex -> sub-class
+    DenseMap<Record*, CodeGenRegisterClass*> SubClassWithSubReg;
+
   public:
     unsigned EnumValue;
     std::string Namespace;
@@ -145,6 +148,16 @@ namespace llvm {
       return SubClasses.test(RC->EnumValue);
     }
 
+    // getSubClassWithSubReg - Returns the largest sub-class where all
+    // registers have a SubIdx sub-register.
+    CodeGenRegisterClass *getSubClassWithSubReg(Record *SubIdx) const {
+      return SubClassWithSubReg.lookup(SubIdx);
+    }
+
+    void setSubClassWithSubReg(Record *SubIdx, CodeGenRegisterClass *SubRC) {
+      SubClassWithSubReg[SubIdx] = SubRC;
+    }
+
     // getSubClasses - Returns a constant BitVector of subclasses indexed by
     // EnumValue.
     // The SubClasses vector includs an entry for this class.