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Detect proper register sub-classes.
Some instructions require restricted register classes, but most of the time that doesn't affect register allocation. For example, some instructions don't work with the stack pointer, but that is a reserved register anyway. Sometimes it matters, GR32_ABCD only has 4 allocatable registers. For such a proper sub-class, the register allocator should try to enable register class inflation since that makes more registers available for allocation. Make sure only legal super-classes are considered. For example, tGPR is not a proper sub-class in Thumb mode, but in ARM mode it is. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136981 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -99,11 +99,16 @@ void RegisterClassInfo::compute(const TargetRegisterClass *RC) const {
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// CSR aliases go after the volatile registers, preserve the target's order.
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std::copy(CSRAlias.begin(), CSRAlias.end(), &RCI.Order[N]);
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// Check if RC is a proper sub-class.
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if (const TargetRegisterClass *Super = TRI->getLargestLegalSuperClass(RC))
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if (Super != RC && getNumAllocatableRegs(Super) > RCI.NumRegs)
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RCI.ProperSubClass = true;
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DEBUG({
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dbgs() << "AllocationOrder(" << RC->getName() << ") = [";
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for (unsigned I = 0; I != RCI.NumRegs; ++I)
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dbgs() << ' ' << PrintReg(RCI.Order[I], TRI);
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dbgs() << " ]\n";
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dbgs() << (RCI.ProperSubClass ? " ] (sub-class)\n" : " ]\n");
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});
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// RCI is now up-to-date.
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@ -28,9 +28,10 @@ class RegisterClassInfo {
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struct RCInfo {
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unsigned Tag;
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unsigned NumRegs;
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bool ProperSubClass;
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OwningArrayPtr<unsigned> Order;
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RCInfo() : Tag(0), NumRegs(0) {}
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RCInfo() : Tag(0), NumRegs(0), ProperSubClass(false) {}
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operator ArrayRef<unsigned>() const {
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return makeArrayRef(Order.get(), NumRegs);
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}
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@ -87,6 +88,16 @@ public:
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return get(RC);
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}
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/// isProperSubClass - Returns true if RC has a legal super-class with more
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/// allocatable registers.
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///
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/// Register classes like GR32_NOSP are not proper sub-classes because %esp
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/// is not allocatable. Similarly, tGPR is not a proper sub-class in Thumb
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/// mode because the GPR super-class is not legal.
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bool isProperSubClass(const TargetRegisterClass *RC) const {
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return get(RC).ProperSubClass;
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}
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/// getLastCalleeSavedAlias - Returns the last callee saved register that
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/// overlaps PhysReg, or 0 if Reg doesn't overlap a CSR.
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unsigned getLastCalleeSavedAlias(unsigned PhysReg) const {
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