Fold trivial two-operand tokenfactors where the operands are equal

[oota-llvm.git] / lib / CodeGen / LowerSubregs.cpp

diff --git a/lib/CodeGen/LowerSubregs.cpp b/lib/CodeGen/LowerSubregs.cpp
index 30894ad6ad71fa3f84b49c4afe489fdf13706a93..f9cef4ccfb7880cb02166a6638fa766c371d2c66 100644 (file)
--- a/lib/CodeGen/LowerSubregs.cpp
+++ b/lib/CodeGen/LowerSubregs.cpp
@@ -6,6 +6,13 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// This file defines a MachineFunction pass which runs after register
+// allocation that turns subreg insert/extract instructions into register
+// copies, as needed. This ensures correct codegen even if the coalescer
+// isn't able to remove all subreg instructions.
+//
+//===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "lowersubregs"
 #include "llvm/CodeGen/Passes.h"
@@ -24,12 +31,18 @@ namespace {
   struct VISIBILITY_HIDDEN LowerSubregsInstructionPass
    : public MachineFunctionPass {
     static char ID; // Pass identification, replacement for typeid
-    LowerSubregsInstructionPass() : MachineFunctionPass((intptr_t)&ID) {}
+    LowerSubregsInstructionPass() : MachineFunctionPass(&ID) {}
     
     const char *getPassName() const {
       return "Subregister lowering instruction pass";
     }
 
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addPreservedID(MachineLoopInfoID);
+      AU.addPreservedID(MachineDominatorsID);
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+
     /// runOnMachineFunction - pass entry point
     bool runOnMachineFunction(MachineFunction&);
     
@@ -118,8 +131,8 @@ bool LowerSubregsInstructionPass::LowerSubregToReg(MachineInstr *MI) {
     TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
 
 #ifndef NDEBUG
-  MachineBasicBlock::iterator dMI = MI;
-  DOUT << "subreg: " << *(--dMI);
+    MachineBasicBlock::iterator dMI = MI;
+    DOUT << "subreg: " << *(--dMI);
 #endif
   }