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98 lines
3.4 KiB
C++
98 lines
3.4 KiB
C++
//===-- llvm/Target/TargetFrameInfo.h ---------------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Interface to describe the layout of a stack frame on the target machine.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TARGET_TARGETFRAMEINFO_H
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#define LLVM_TARGET_TARGETFRAMEINFO_H
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#include <utility>
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namespace llvm {
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/// Information about stack frame layout on the target. It holds the direction
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/// of stack growth, the known stack alignment on entry to each function, and
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/// the offset to the locals area.
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///
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/// The offset to the local area is the offset from the stack pointer on
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/// function entry to the first location where function data (local variables,
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/// spill locations) can be stored.
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class TargetFrameInfo {
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public:
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enum StackDirection {
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StackGrowsUp, // Adding to the stack increases the stack address
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StackGrowsDown // Adding to the stack decreases the stack address
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};
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// Maps a callee saved register to a stack slot with a fixed offset.
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struct SpillSlot {
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unsigned Reg;
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int Offset; // Offset relative to stack pointer on function entry.
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};
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private:
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StackDirection StackDir;
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unsigned StackAlignment;
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unsigned TransientStackAlignment;
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int LocalAreaOffset;
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public:
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TargetFrameInfo(StackDirection D, unsigned StackAl, int LAO,
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unsigned TransAl = 1)
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: StackDir(D), StackAlignment(StackAl), TransientStackAlignment(TransAl),
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LocalAreaOffset(LAO) {}
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virtual ~TargetFrameInfo();
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// These methods return information that describes the abstract stack layout
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// of the target machine.
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/// getStackGrowthDirection - Return the direction the stack grows
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///
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StackDirection getStackGrowthDirection() const { return StackDir; }
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/// getStackAlignment - This method returns the number of bytes to which the
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/// stack pointer must be aligned on entry to a function. Typically, this
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/// is the largest alignment for any data object in the target.
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///
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unsigned getStackAlignment() const { return StackAlignment; }
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/// getTransientStackAlignment - This method returns the number of bytes to
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/// which the stack pointer must be aligned at all times, even between
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/// calls.
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///
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unsigned getTransientStackAlignment() const {
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return TransientStackAlignment;
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}
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/// getOffsetOfLocalArea - This method returns the offset of the local area
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/// from the stack pointer on entrance to a function.
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///
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int getOffsetOfLocalArea() const { return LocalAreaOffset; }
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/// getCalleeSavedSpillSlots - This method returns a pointer to an array of
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/// pairs, that contains an entry for each callee saved register that must be
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/// spilled to a particular stack location if it is spilled.
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///
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/// Each entry in this array contains a <register,offset> pair, indicating the
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/// fixed offset from the incoming stack pointer that each register should be
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/// spilled at. If a register is not listed here, the code generator is
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/// allowed to spill it anywhere it chooses.
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///
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virtual const SpillSlot *
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getCalleeSavedSpillSlots(unsigned &NumEntries) const {
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NumEntries = 0;
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return 0;
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}
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};
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} // End llvm namespace
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#endif
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