Add a new method which enables one to change register classes.

See the Mips16ISetLowering.cpp patch to see a use of this.
For now now the extra code in Mips16ISetLowering.cpp is a nop but is
used for test purposes. Mips32 registers are setup and then removed and
then the Mips16 registers are setup. 

Normally you need to add register classes and then call
computeRegisterProperties.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177120 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 15 insertions, 0 deletions

diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index e3e5737300..5d74848b71 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -958,6 +958,13 @@ protected:
     RegClassForVT[VT.SimpleTy] = RC;
   }
 
+  /// clearRegisterClasses - remove all register classes
+  void clearRegisterClasses() {
+    for (unsigned i = 0 ; i<array_lengthof(RegClassForVT); i++)
+      RegClassForVT[i] = 0;
+    AvailableRegClasses.clear();
+  }
+
   /// findRepresentativeClass - Return the largest legal super-reg register class
   /// of the register class for the specified type and its associated "cost".
   virtual std::pair<const TargetRegisterClass*, uint8_t>
diff --git a/lib/Target/Mips/Mips16ISelLowering.cpp b/lib/Target/Mips/Mips16ISelLowering.cpp
index 6de62cfab3..23eb5375ac 100644
--- a/lib/Target/Mips/Mips16ISelLowering.cpp
+++ b/lib/Target/Mips/Mips16ISelLowering.cpp
@@ -39,6 +39,14 @@ namespace {
 
 Mips16TargetLowering::Mips16TargetLowering(MipsTargetMachine &TM)
   : MipsTargetLowering(TM) {
+  //
+  // set up as if mips32 and then revert so we can test the mechanism
+  // for switching
+  addRegisterClass(MVT::i32, &Mips::CPURegsRegClass);
+  addRegisterClass(MVT::f32, &Mips::FGR32RegClass);
+  computeRegisterProperties();
+  clearRegisterClasses();
+
   // Set up the register classes
   addRegisterClass(MVT::i32, &Mips::CPU16RegsRegClass);