Add an option to use a virtual register as the global base register instead of

reserving a physical register ($gp or $28) for that purpose.

This will completely eliminate loads that restore the value of $gp after every
function call, if the register allocator assigns a callee-saved register, or
eliminate unnecessary loads if it assigns a temporary register. 

example:

.cpload $25       // set $gp.
...
.cprestore 16     // store $gp to stack slot 16($sp).
...
jalr $25          // function call. clobbers $gp.
lw $gp, 16($sp)   // not emitted if callee-saved reg is chosen.
...
lw $2, 4($gp)
...
jalr $25          // function call.
lw $gp, 16($sp)   // not emitted if $gp is not live after this instruction.
...



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151402 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 6 deletions

diff --git a/lib/Target/Mips/MipsInstrInfo.h b/lib/Target/Mips/MipsInstrInfo.h
index 70cc2cfb1a..8a83685eb5 100644
--- a/lib/Target/Mips/MipsInstrInfo.h
+++ b/lib/Target/Mips/MipsInstrInfo.h
@@ -103,12 +103,6 @@ public:
   /// Insert nop instruction when hazard condition is found
   virtual void insertNoop(MachineBasicBlock &MBB,
                           MachineBasicBlock::iterator MI) const;
-
-  /// getGlobalBaseReg - Return a virtual register initialized with the
-  /// the global base register value. Output instructions required to
-  /// initialize the register in the function entry block, if necessary.
-  ///
-  unsigned getGlobalBaseReg(MachineFunction *MF) const;
 };
 
 }