Line data Source code
1 : //===-- llvm/CodeGen/TargetFrameLowering.h ----------------------*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 : //
10 : // Interface to describe the layout of a stack frame on the target machine.
11 : //
12 : //===----------------------------------------------------------------------===//
13 :
14 : #ifndef LLVM_CODEGEN_TARGETFRAMELOWERING_H
15 : #define LLVM_CODEGEN_TARGETFRAMELOWERING_H
16 :
17 : #include "llvm/CodeGen/MachineBasicBlock.h"
18 : #include <utility>
19 : #include <vector>
20 :
21 : namespace llvm {
22 : class BitVector;
23 : class CalleeSavedInfo;
24 : class MachineFunction;
25 : class RegScavenger;
26 :
27 : /// Information about stack frame layout on the target. It holds the direction
28 : /// of stack growth, the known stack alignment on entry to each function, and
29 : /// the offset to the locals area.
30 : ///
31 : /// The offset to the local area is the offset from the stack pointer on
32 : /// function entry to the first location where function data (local variables,
33 : /// spill locations) can be stored.
34 34778 : class TargetFrameLowering {
35 : public:
36 : enum StackDirection {
37 : StackGrowsUp, // Adding to the stack increases the stack address
38 : StackGrowsDown // Adding to the stack decreases the stack address
39 : };
40 :
41 : // Maps a callee saved register to a stack slot with a fixed offset.
42 : struct SpillSlot {
43 : unsigned Reg;
44 : int Offset; // Offset relative to stack pointer on function entry.
45 : };
46 : private:
47 : StackDirection StackDir;
48 : unsigned StackAlignment;
49 : unsigned TransientStackAlignment;
50 : int LocalAreaOffset;
51 : bool StackRealignable;
52 : public:
53 : TargetFrameLowering(StackDirection D, unsigned StackAl, int LAO,
54 : unsigned TransAl = 1, bool StackReal = true)
55 41319 : : StackDir(D), StackAlignment(StackAl), TransientStackAlignment(TransAl),
56 41319 : LocalAreaOffset(LAO), StackRealignable(StackReal) {}
57 :
58 : virtual ~TargetFrameLowering();
59 :
60 : // These methods return information that describes the abstract stack layout
61 : // of the target machine.
62 :
63 : /// getStackGrowthDirection - Return the direction the stack grows
64 : ///
65 0 : StackDirection getStackGrowthDirection() const { return StackDir; }
66 :
67 : /// getStackAlignment - This method returns the number of bytes to which the
68 : /// stack pointer must be aligned on entry to a function. Typically, this
69 : /// is the largest alignment for any data object in the target.
70 : ///
71 0 : unsigned getStackAlignment() const { return StackAlignment; }
72 :
73 : /// alignSPAdjust - This method aligns the stack adjustment to the correct
74 : /// alignment.
75 : ///
76 0 : int alignSPAdjust(int SPAdj) const {
77 142 : if (SPAdj < 0) {
78 0 : SPAdj = -alignTo(-SPAdj, StackAlignment);
79 : } else {
80 284 : SPAdj = alignTo(SPAdj, StackAlignment);
81 : }
82 0 : return SPAdj;
83 : }
84 :
85 : /// getTransientStackAlignment - This method returns the number of bytes to
86 : /// which the stack pointer must be aligned at all times, even between
87 : /// calls.
88 : ///
89 0 : unsigned getTransientStackAlignment() const {
90 0 : return TransientStackAlignment;
91 : }
92 :
93 : /// isStackRealignable - This method returns whether the stack can be
94 : /// realigned.
95 0 : bool isStackRealignable() const {
96 0 : return StackRealignable;
97 : }
98 :
99 : /// Return the skew that has to be applied to stack alignment under
100 : /// certain conditions (e.g. stack was adjusted before function \p MF
101 : /// was called).
102 : virtual unsigned getStackAlignmentSkew(const MachineFunction &MF) const;
103 :
104 : /// getOffsetOfLocalArea - This method returns the offset of the local area
105 : /// from the stack pointer on entrance to a function.
106 : ///
107 0 : int getOffsetOfLocalArea() const { return LocalAreaOffset; }
108 :
109 : /// isFPCloseToIncomingSP - Return true if the frame pointer is close to
110 : /// the incoming stack pointer, false if it is close to the post-prologue
111 : /// stack pointer.
112 204782 : virtual bool isFPCloseToIncomingSP() const { return true; }
113 :
114 : /// assignCalleeSavedSpillSlots - Allows target to override spill slot
115 : /// assignment logic. If implemented, assignCalleeSavedSpillSlots() should
116 : /// assign frame slots to all CSI entries and return true. If this method
117 : /// returns false, spill slots will be assigned using generic implementation.
118 : /// assignCalleeSavedSpillSlots() may add, delete or rearrange elements of
119 : /// CSI.
120 : virtual bool
121 82654 : assignCalleeSavedSpillSlots(MachineFunction &MF,
122 : const TargetRegisterInfo *TRI,
123 : std::vector<CalleeSavedInfo> &CSI) const {
124 82654 : return false;
125 : }
126 :
127 : /// getCalleeSavedSpillSlots - This method returns a pointer to an array of
128 : /// pairs, that contains an entry for each callee saved register that must be
129 : /// spilled to a particular stack location if it is spilled.
130 : ///
131 : /// Each entry in this array contains a <register,offset> pair, indicating the
132 : /// fixed offset from the incoming stack pointer that each register should be
133 : /// spilled at. If a register is not listed here, the code generator is
134 : /// allowed to spill it anywhere it chooses.
135 : ///
136 : virtual const SpillSlot *
137 8048 : getCalleeSavedSpillSlots(unsigned &NumEntries) const {
138 8048 : NumEntries = 0;
139 8048 : return nullptr;
140 : }
141 :
142 : /// targetHandlesStackFrameRounding - Returns true if the target is
143 : /// responsible for rounding up the stack frame (probably at emitPrologue
144 : /// time).
145 390874 : virtual bool targetHandlesStackFrameRounding() const {
146 390874 : return false;
147 : }
148 :
149 : /// Returns true if the target will correctly handle shrink wrapping.
150 33847 : virtual bool enableShrinkWrapping(const MachineFunction &MF) const {
151 33847 : return false;
152 : }
153 :
154 : /// Returns true if the stack slot holes in the fixed and callee-save stack
155 : /// area should be used when allocating other stack locations to reduce stack
156 : /// size.
157 12795 : virtual bool enableStackSlotScavenging(const MachineFunction &MF) const {
158 12795 : return false;
159 : }
160 :
161 : /// Returns true if the target can safely skip saving callee-saved registers
162 : /// for noreturn nounwind functions.
163 : virtual bool enableCalleeSaveSkip(const MachineFunction &MF) const;
164 :
165 : /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
166 : /// the function.
167 : virtual void emitPrologue(MachineFunction &MF,
168 : MachineBasicBlock &MBB) const = 0;
169 : virtual void emitEpilogue(MachineFunction &MF,
170 : MachineBasicBlock &MBB) const = 0;
171 :
172 : /// Replace a StackProbe stub (if any) with the actual probe code inline
173 90484 : virtual void inlineStackProbe(MachineFunction &MF,
174 90484 : MachineBasicBlock &PrologueMBB) const {}
175 :
176 : /// Adjust the prologue to have the function use segmented stacks. This works
177 : /// by adding a check even before the "normal" function prologue.
178 0 : virtual void adjustForSegmentedStacks(MachineFunction &MF,
179 0 : MachineBasicBlock &PrologueMBB) const {}
180 :
181 : /// Adjust the prologue to add Erlang Run-Time System (ERTS) specific code in
182 : /// the assembly prologue to explicitly handle the stack.
183 0 : virtual void adjustForHiPEPrologue(MachineFunction &MF,
184 0 : MachineBasicBlock &PrologueMBB) const {}
185 :
186 : /// spillCalleeSavedRegisters - Issues instruction(s) to spill all callee
187 : /// saved registers and returns true if it isn't possible / profitable to do
188 : /// so by issuing a series of store instructions via
189 : /// storeRegToStackSlot(). Returns false otherwise.
190 127 : virtual bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
191 : MachineBasicBlock::iterator MI,
192 : const std::vector<CalleeSavedInfo> &CSI,
193 : const TargetRegisterInfo *TRI) const {
194 127 : return false;
195 : }
196 :
197 : /// restoreCalleeSavedRegisters - Issues instruction(s) to restore all callee
198 : /// saved registers and returns true if it isn't possible / profitable to do
199 : /// so by issuing a series of load instructions via loadRegToStackSlot().
200 : /// If it returns true, and any of the registers in CSI is not restored,
201 : /// it sets the corresponding Restored flag in CSI to false.
202 : /// Returns false otherwise.
203 2100 : virtual bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
204 : MachineBasicBlock::iterator MI,
205 : std::vector<CalleeSavedInfo> &CSI,
206 : const TargetRegisterInfo *TRI) const {
207 2100 : return false;
208 : }
209 :
210 : /// Return true if the target needs to disable frame pointer elimination.
211 : virtual bool noFramePointerElim(const MachineFunction &MF) const;
212 :
213 : /// hasFP - Return true if the specified function should have a dedicated
214 : /// frame pointer register. For most targets this is true only if the function
215 : /// has variable sized allocas or if frame pointer elimination is disabled.
216 : virtual bool hasFP(const MachineFunction &MF) const = 0;
217 :
218 : /// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
219 : /// not required, we reserve argument space for call sites in the function
220 : /// immediately on entry to the current function. This eliminates the need for
221 : /// add/sub sp brackets around call sites. Returns true if the call frame is
222 : /// included as part of the stack frame.
223 6720 : virtual bool hasReservedCallFrame(const MachineFunction &MF) const {
224 6720 : return !hasFP(MF);
225 : }
226 :
227 : /// canSimplifyCallFramePseudos - When possible, it's best to simplify the
228 : /// call frame pseudo ops before doing frame index elimination. This is
229 : /// possible only when frame index references between the pseudos won't
230 : /// need adjusting for the call frame adjustments. Normally, that's true
231 : /// if the function has a reserved call frame or a frame pointer. Some
232 : /// targets (Thumb2, for example) may have more complicated criteria,
233 : /// however, and can override this behavior.
234 16644 : virtual bool canSimplifyCallFramePseudos(const MachineFunction &MF) const {
235 16644 : return hasReservedCallFrame(MF) || hasFP(MF);
236 : }
237 :
238 : // needsFrameIndexResolution - Do we need to perform FI resolution for
239 : // this function. Normally, this is required only when the function
240 : // has any stack objects. However, targets may want to override this.
241 : virtual bool needsFrameIndexResolution(const MachineFunction &MF) const;
242 :
243 : /// getFrameIndexReference - This method should return the base register
244 : /// and offset used to reference a frame index location. The offset is
245 : /// returned directly, and the base register is returned via FrameReg.
246 : virtual int getFrameIndexReference(const MachineFunction &MF, int FI,
247 : unsigned &FrameReg) const;
248 :
249 : /// Same as \c getFrameIndexReference, except that the stack pointer (as
250 : /// opposed to the frame pointer) will be the preferred value for \p
251 : /// FrameReg. This is generally used for emitting statepoint or EH tables that
252 : /// use offsets from RSP. If \p IgnoreSPUpdates is true, the returned
253 : /// offset is only guaranteed to be valid with respect to the value of SP at
254 : /// the end of the prologue.
255 0 : virtual int getFrameIndexReferencePreferSP(const MachineFunction &MF, int FI,
256 : unsigned &FrameReg,
257 : bool IgnoreSPUpdates) const {
258 : // Always safe to dispatch to getFrameIndexReference.
259 0 : return getFrameIndexReference(MF, FI, FrameReg);
260 : }
261 :
262 : /// This method determines which of the registers reported by
263 : /// TargetRegisterInfo::getCalleeSavedRegs() should actually get saved.
264 : /// The default implementation checks populates the \p SavedRegs bitset with
265 : /// all registers which are modified in the function, targets may override
266 : /// this function to save additional registers.
267 : /// This method also sets up the register scavenger ensuring there is a free
268 : /// register or a frameindex available.
269 : virtual void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
270 : RegScavenger *RS = nullptr) const;
271 :
272 : /// processFunctionBeforeFrameFinalized - This method is called immediately
273 : /// before the specified function's frame layout (MF.getFrameInfo()) is
274 : /// finalized. Once the frame is finalized, MO_FrameIndex operands are
275 : /// replaced with direct constants. This method is optional.
276 : ///
277 48672 : virtual void processFunctionBeforeFrameFinalized(MachineFunction &MF,
278 : RegScavenger *RS = nullptr) const {
279 48672 : }
280 :
281 0 : virtual unsigned getWinEHParentFrameOffset(const MachineFunction &MF) const {
282 0 : report_fatal_error("WinEH not implemented for this target");
283 : }
284 :
285 : /// This method is called during prolog/epilog code insertion to eliminate
286 : /// call frame setup and destroy pseudo instructions (but only if the Target
287 : /// is using them). It is responsible for eliminating these instructions,
288 : /// replacing them with concrete instructions. This method need only be
289 : /// implemented if using call frame setup/destroy pseudo instructions.
290 : /// Returns an iterator pointing to the instruction after the replaced one.
291 : virtual MachineBasicBlock::iterator
292 0 : eliminateCallFramePseudoInstr(MachineFunction &MF,
293 : MachineBasicBlock &MBB,
294 : MachineBasicBlock::iterator MI) const {
295 0 : llvm_unreachable("Call Frame Pseudo Instructions do not exist on this "
296 : "target!");
297 : }
298 :
299 :
300 : /// Order the symbols in the local stack frame.
301 : /// The list of objects that we want to order is in \p objectsToAllocate as
302 : /// indices into the MachineFrameInfo. The array can be reordered in any way
303 : /// upon return. The contents of the array, however, may not be modified (i.e.
304 : /// only their order may be changed).
305 : /// By default, just maintain the original order.
306 : virtual void
307 85237 : orderFrameObjects(const MachineFunction &MF,
308 : SmallVectorImpl<int> &objectsToAllocate) const {
309 85237 : }
310 :
311 : /// Check whether or not the given \p MBB can be used as a prologue
312 : /// for the target.
313 : /// The prologue will be inserted first in this basic block.
314 : /// This method is used by the shrink-wrapping pass to decide if
315 : /// \p MBB will be correctly handled by the target.
316 : /// As soon as the target enable shrink-wrapping without overriding
317 : /// this method, we assume that each basic block is a valid
318 : /// prologue.
319 169 : virtual bool canUseAsPrologue(const MachineBasicBlock &MBB) const {
320 169 : return true;
321 : }
322 :
323 : /// Check whether or not the given \p MBB can be used as a epilogue
324 : /// for the target.
325 : /// The epilogue will be inserted before the first terminator of that block.
326 : /// This method is used by the shrink-wrapping pass to decide if
327 : /// \p MBB will be correctly handled by the target.
328 : /// As soon as the target enable shrink-wrapping without overriding
329 : /// this method, we assume that each basic block is a valid
330 : /// epilogue.
331 224 : virtual bool canUseAsEpilogue(const MachineBasicBlock &MBB) const {
332 224 : return true;
333 : }
334 :
335 : /// Check if given function is safe for not having callee saved registers.
336 : /// This is used when interprocedural register allocation is enabled.
337 58351 : static bool isSafeForNoCSROpt(const Function &F) {
338 6 : if (!F.hasLocalLinkage() || F.hasAddressTaken() ||
339 : !F.hasFnAttribute(Attribute::NoRecurse))
340 58348 : return false;
341 : // Function should not be optimized as tail call.
342 6 : for (const User *U : F.users())
343 3 : if (auto CS = ImmutableCallSite(U))
344 : if (CS.isTailCall())
345 : return false;
346 : return true;
347 : }
348 :
349 : /// Return initial CFA offset value i.e. the one valid at the beginning of the
350 : /// function (before any stack operations).
351 : virtual int getInitialCFAOffset(const MachineFunction &MF) const;
352 :
353 : /// Return initial CFA register value i.e. the one valid at the beginning of
354 : /// the function (before any stack operations).
355 : virtual unsigned getInitialCFARegister(const MachineFunction &MF) const;
356 : };
357 :
358 : } // End llvm namespace
359 :
360 : #endif
|
