represent combinations of constraints from instructions and sub-registers.
The synthetic register classes inherit most of their properties form their
closest user-defined super-class.</li>
+ <li><code>MachineRegisterInfo</code> now allows the reserved registers to be
+ frozen when register allocation starts. Target hooks should use the
+ <code>MRI->canReserveReg(FramePtr)</code> method to avoid accidentally
+ disabling frame pointer elimination during register allocation.</li>
</ul>
</div>
/// so that the code generator knows which callee save registers to save and
/// for other target specific uses.
BitVector UsedPhysRegs;
-
+
+ /// ReservedRegs - This is a bit vector of reserved registers. The target
+ /// may change its mind about which registers should be reserved. This
+ /// vector is the frozen set of reserved registers when register allocation
+ /// started.
+ BitVector ReservedRegs;
+
/// LiveIns/LiveOuts - Keep track of the physical registers that are
/// livein/liveout of the function. Live in values are typically arguments in
/// registers, live out values are typically return values in registers.
/// subregisters. That means that if R is used, so are all subregisters.
void closePhysRegsUsed(const TargetRegisterInfo&);
+
+ //===--------------------------------------------------------------------===//
+ // Reserved Register Info
+ //===--------------------------------------------------------------------===//
+ //
+ // The set of reserved registers must be invariant during register
+ // allocation. For example, the target cannot suddenly decide it needs a
+ // frame pointer when the register allocator has already used the frame
+ // pointer register for something else.
+ //
+ // These methods can be used by target hooks like hasFP() to avoid changing
+ // the reserved register set during register allocation.
+
+ /// freezeReservedRegs - Called by the register allocator to freeze the set
+ /// of reserved registers before allocation begins.
+ void freezeReservedRegs(const MachineFunction&);
+
+ /// reservedRegsFrozen - Returns true after freezeReservedRegs() was called
+ /// to ensure the set of reserved registers stays constant.
+ bool reservedRegsFrozen() const {
+ return !ReservedRegs.empty();
+ }
+
+ /// canReserveReg - Returns true if PhysReg can be used as a reserved
+ /// register. Any register can be reserved before freezeReservedRegs() is
+ /// called.
+ bool canReserveReg(unsigned PhysReg) const {
+ return !reservedRegsFrozen() || ReservedRegs.test(PhysReg);
+ }
+
+
//===--------------------------------------------------------------------===//
// LiveIn/LiveOut Management
//===--------------------------------------------------------------------===//