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7fc5011e8d
The ELFv2 ABI reduces the amount of stack required to implement an ABI-compliant function call in two ways: * the "linkage area" is reduced from 48 bytes to 32 bytes by eliminating two unused doublewords * the 64-byte "parameter save area" is now optional and need not be present in certain cases (it remains mandatory in functions with variable arguments, and functions that have any parameter that is passed on the stack) The following patch implements this required changes: - reducing the linkage area, and associated relocation of the TOC save slot, in getLinkageSize / getTOCSaveOffset (this requires updating all callers of these routines to pass in the isELFv2ABI flag). - (partially) handling the case where the parameter save are is optional This latter part requires some extra explanation: Currently, we still always allocate the parameter save area when *calling* a function. That is certainly always compliant with the ABI, but may cause code to allocate stack unnecessarily. This can be addressed by a follow-on optimization patch. On the *callee* side, in LowerFormalArguments, we *must* track correctly whether the ABI guarantees that the caller has allocated the parameter save area for our use, and the patch does so. However, there is one complication: the code that handles incoming "byval" arguments will currently *always* write to the parameter save area, because it has to force incoming register arguments to the stack since it must return an *address* to implement the byval semantics. To fix this, the patch changes the LowerFormalArguments code to write arguments to a freshly allocated stack slot on the function's own stack frame instead of the argument save area in those cases where that area is not present. Reviewed by Hal Finkel. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213490 91177308-0d34-0410-b5e6-96231b3b80d8
127 lines
4.6 KiB
C++
127 lines
4.6 KiB
C++
//===-- PPCFrameLowering.h - Define frame lowering for PowerPC --*- 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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//
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//===----------------------------------------------------------------------===//
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#ifndef POWERPC_FRAMEINFO_H
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#define POWERPC_FRAMEINFO_H
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#include "PPC.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Target/TargetFrameLowering.h"
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#include "llvm/Target/TargetMachine.h"
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namespace llvm {
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class PPCSubtarget;
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class PPCFrameLowering: public TargetFrameLowering {
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const PPCSubtarget &Subtarget;
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public:
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PPCFrameLowering(const PPCSubtarget &STI);
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unsigned determineFrameLayout(MachineFunction &MF,
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bool UpdateMF = true,
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bool UseEstimate = false) const;
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/// emitProlog/emitEpilog - These methods insert prolog and epilog code into
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/// the function.
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void emitPrologue(MachineFunction &MF) const override;
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void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
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bool hasFP(const MachineFunction &MF) const override;
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bool needsFP(const MachineFunction &MF) const;
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void replaceFPWithRealFP(MachineFunction &MF) const;
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void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
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RegScavenger *RS = nullptr) const override;
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void processFunctionBeforeFrameFinalized(MachineFunction &MF,
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RegScavenger *RS = nullptr) const override;
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void addScavengingSpillSlot(MachineFunction &MF, RegScavenger *RS) const;
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bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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const std::vector<CalleeSavedInfo> &CSI,
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const TargetRegisterInfo *TRI) const override;
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void eliminateCallFramePseudoInstr(MachineFunction &MF,
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MachineBasicBlock &MBB,
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MachineBasicBlock::iterator I) const override;
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bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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const std::vector<CalleeSavedInfo> &CSI,
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const TargetRegisterInfo *TRI) const override;
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/// targetHandlesStackFrameRounding - Returns true if the target is
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/// responsible for rounding up the stack frame (probably at emitPrologue
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/// time).
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bool targetHandlesStackFrameRounding() const override { return true; }
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/// getReturnSaveOffset - Return the previous frame offset to save the
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/// return address.
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static unsigned getReturnSaveOffset(bool isPPC64, bool isDarwinABI) {
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if (isDarwinABI)
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return isPPC64 ? 16 : 8;
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// SVR4 ABI:
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return isPPC64 ? 16 : 4;
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}
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/// getTOCSaveOffset - Return the previous frame offset to save the
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/// TOC register -- 64-bit SVR4 ABI only.
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static unsigned getTOCSaveOffset(bool isELFv2ABI) {
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return isELFv2ABI ? 24 : 40;
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}
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/// getFramePointerSaveOffset - Return the previous frame offset to save the
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/// frame pointer.
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static unsigned getFramePointerSaveOffset(bool isPPC64, bool isDarwinABI) {
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// For the Darwin ABI:
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// We cannot use the TOC save slot (offset +20) in the PowerPC linkage area
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// for saving the frame pointer (if needed.) While the published ABI has
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// not used this slot since at least MacOSX 10.2, there is older code
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// around that does use it, and that needs to continue to work.
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if (isDarwinABI)
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return isPPC64 ? -8U : -4U;
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// SVR4 ABI: First slot in the general register save area.
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return isPPC64 ? -8U : -4U;
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}
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/// getBasePointerSaveOffset - Return the previous frame offset to save the
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/// base pointer.
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static unsigned getBasePointerSaveOffset(bool isPPC64,
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bool isDarwinABI,
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bool isPIC) {
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if (isDarwinABI)
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return isPPC64 ? -16U : -8U;
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// SVR4 ABI: First slot in the general register save area.
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return isPPC64 ? -16U : isPIC ? -12U : -8U;
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}
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/// getLinkageSize - Return the size of the PowerPC ABI linkage area.
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///
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static unsigned getLinkageSize(bool isPPC64, bool isDarwinABI,
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bool isELFv2ABI) {
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if (isDarwinABI || isPPC64)
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return (isELFv2ABI ? 4 : 6) * (isPPC64 ? 8 : 4);
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// SVR4 ABI:
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return 8;
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}
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const SpillSlot *
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getCalleeSavedSpillSlots(unsigned &NumEntries) const override;
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};
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} // End llvm namespace
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#endif
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