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/* -----------------------------------------------------------------------------
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* (c) The GHC Team, 1998-2009
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* Registers in the STG machine.
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* Do not #include this file directly: #include "Rts.h" instead.
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* To understand the structure of the RTS headers, see the wiki:
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* http://hackage.haskell.org/trac/ghc/wiki/Commentary/SourceTree/Includes
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* ---------------------------------------------------------------------------*/
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* The STG machine has a collection of "registers", each one of which
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* may or may not correspond to an actual machine register when
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* The register set is backed by a table in memory (struct
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* StgRegTable). If a particular STG register is not mapped to a
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* machine register, then the apprpriate slot in this table is used
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* This table is itself pointed to by another register, BaseReg. If
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* BaseReg is not in a machine register, then the register table is
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* used from an absolute location (MainCapability).
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StgWord stgEagerBlackholeInfo;
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StgFunPtr stgGCEnter1;
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* Vanilla registers are given this union type, which is purely so
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* that we can cast the vanilla reg to a variety of types with the
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* minimum of syntax. eg. R1.w instead of (StgWord)R1.
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* This is the table that holds shadow-locations for all the STG
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* registers. The shadow locations are used when:
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* 1) the particular register isn't mapped to a real machine
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* register, probably because there's a shortage of real registers.
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* 2) caller-saves registers are saved across a CCall
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typedef struct StgRegTable_ {
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StgUnion rR9; /* used occasionally by heap/stack checks */
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StgUnion rR10; /* used occasionally by heap/stack checks */
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struct StgTSO_ * rCurrentTSO;
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struct nursery_ * rNursery;
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struct bdescr_ * rCurrentNursery; /* Hp/HpLim point into this block */
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struct bdescr_ * rCurrentAlloc; /* for allocation using allocate() */
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StgWord rHpAlloc; /* number of *bytes* being allocated in heap */
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StgWord rRet; // holds the return code of the thread
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* Registers Hp and HpLim are global across the entire system, and are
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* copied into the RegTable before executing a thread.
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* Registers Sp and SpLim are saved in the TSO for the
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* thread, but are copied into the RegTable before executing a thread.
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* All other registers are "general purpose", and are used for passing
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* arguments to functions, and returning values. The code generator
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* knows how many of these are in real registers, and avoids
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* generating code that uses non-real registers. General purpose
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* registers are never saved when returning to the scheduler, instead
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* we save whatever is live at the time on the stack, and restore it
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* later. This should reduce the context switch time, amongst other
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* For argument passing, the stack will be used in preference to
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* pseudo-registers if the architecture has too few general purpose
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* Some special RTS functions like newArray and the Integer primitives
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* expect their arguments to be in registers R1-Rn, so we use these
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* (pseudo-)registers in those cases.
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* Locations for saving per-thread registers.
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#define SAVE_Sp (CurrentTSO->sp)
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#define SAVE_SpLim (CurrentTSO->splim)
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#define SAVE_Hp (BaseReg->rHp)
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#define SAVE_CurrentTSO (BaseReg->rCurrentTSO)
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#define SAVE_CurrentNursery (BaseReg->rCurrentNursery)
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#define SAVE_HpAlloc (BaseReg->rHpAlloc)
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/* We sometimes need to save registers across a C-call, eg. if they
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* are clobbered in the standard calling convention. We define the
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* save locations for all registers in the register table.
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#define SAVE_R1 (BaseReg->rR1)
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#define SAVE_R2 (BaseReg->rR2)
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#define SAVE_R3 (BaseReg->rR3)
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#define SAVE_R4 (BaseReg->rR4)
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#define SAVE_R5 (BaseReg->rR5)
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#define SAVE_R6 (BaseReg->rR6)
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#define SAVE_R7 (BaseReg->rR7)
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#define SAVE_R8 (BaseReg->rR8)
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#define SAVE_F1 (BaseReg->rF1)
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#define SAVE_F2 (BaseReg->rF2)
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#define SAVE_F3 (BaseReg->rF3)
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#define SAVE_F4 (BaseReg->rF4)
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#define SAVE_D1 (BaseReg->rD1)
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#define SAVE_D2 (BaseReg->rD2)
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#define SAVE_L1 (BaseReg->rL1)
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/* -----------------------------------------------------------------------------
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* Emit the GCC-specific register declarations for each machine
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* register being used. If any STG register isn't mapped to a machine
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* register, then map it to an offset from BaseReg.
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* First, the general purpose registers. The idea is, if a particular
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* general-purpose STG register can't be mapped to a real machine
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* register, it won't be used at all. Instead, we'll use the stack.
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* This is an improvement on the way things used to be done, when all
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* registers were mapped to locations in the register table, and stuff
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* was being shifted from the stack to the register table and back
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* again for no good reason (on register-poor architectures).
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/* define NO_REGS to omit register declarations - used in RTS C code
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* that needs all the STG definitions but not the global register
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#define GLOBAL_REG_DECL(type,name,reg) register type name REG(reg);
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#if defined(REG_R1) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R1,REG_R1)
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# define R1 (BaseReg->rR1)
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#if defined(REG_R2) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R2,REG_R2)
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# define R2 (BaseReg->rR2)
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#if defined(REG_R3) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R3,REG_R3)
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# define R3 (BaseReg->rR3)
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#if defined(REG_R4) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R4,REG_R4)
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# define R4 (BaseReg->rR4)
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#if defined(REG_R5) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R5,REG_R5)
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# define R5 (BaseReg->rR5)
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#if defined(REG_R6) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R6,REG_R6)
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# define R6 (BaseReg->rR6)
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#if defined(REG_R7) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R7,REG_R7)
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# define R7 (BaseReg->rR7)
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#if defined(REG_R8) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R8,REG_R8)
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# define R8 (BaseReg->rR8)
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#if defined(REG_R9) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R9,REG_R9)
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# define R9 (BaseReg->rR9)
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#if defined(REG_R10) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgUnion,R10,REG_R10)
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# define R10 (BaseReg->rR10)
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#if defined(REG_F1) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgFloat,F1,REG_F1)
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#define F1 (BaseReg->rF1)
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#if defined(REG_F2) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgFloat,F2,REG_F2)
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#define F2 (BaseReg->rF2)
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#if defined(REG_F3) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgFloat,F3,REG_F3)
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#define F3 (BaseReg->rF3)
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#if defined(REG_F4) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgFloat,F4,REG_F4)
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#define F4 (BaseReg->rF4)
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#if defined(REG_D1) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgDouble,D1,REG_D1)
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#define D1 (BaseReg->rD1)
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#if defined(REG_D2) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgDouble,D2,REG_D2)
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#define D2 (BaseReg->rD2)
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#if defined(REG_L1) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgWord64,L1,REG_L1)
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#define L1 (BaseReg->rL1)
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* If BaseReg isn't mapped to a machine register, just use the global
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* address of the current register table (CurrentRegTable in
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* concurrent Haskell, MainRegTable otherwise).
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/* A capability is a combination of a FunTable and a RegTable. In STG
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* code, BaseReg normally points to the RegTable portion of this
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* structure, so that we can index both forwards and backwards to take
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* advantage of shorter instruction forms on some archs (eg. x86).
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* This is a cut-down version of the Capability structure; the full
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* version is defined in Capability.h.
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struct PartCapability_ {
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/* No such thing as a MainCapability under THREADED_RTS - each thread must have
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* its own Capability.
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#if IN_STG_CODE && !(defined(THREADED_RTS) && !defined(NOSMP))
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extern W_ MainCapability[];
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* Assigning to BaseReg (the ASSIGN_BaseReg macro): this happens on
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* return from a "safe" foreign call, when the thread might be running
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* on a new Capability. Obviously if BaseReg is not a register, then
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* we are restricted to a single Capability (this invariant is enforced
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* in Capability.c:initCapabilities), and assigning to BaseReg can be omitted.
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#if defined(REG_Base) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(StgRegTable *,BaseReg,REG_Base)
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#define ASSIGN_BaseReg(e) (BaseReg = (e))
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#if defined(THREADED_RTS) && !defined(NOSMP)
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#error BaseReg must be in a register for THREADED_RTS
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#define BaseReg (&((struct PartCapability_ *)MainCapability)->r)
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#define ASSIGN_BaseReg(e) (e)
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#if defined(REG_Sp) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(P_,Sp,REG_Sp)
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#define Sp (BaseReg->rSp)
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#if defined(REG_SpLim) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(P_,SpLim,REG_SpLim)
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#define SpLim (BaseReg->rSpLim)
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#if defined(REG_Hp) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(P_,Hp,REG_Hp)
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#define Hp (BaseReg->rHp)
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#if defined(REG_HpLim) && !defined(NO_GLOBAL_REG_DECLS)
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#error HpLim cannot be in a register
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#define HpLim (BaseReg->rHpLim)
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#if defined(REG_CurrentTSO) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(struct _StgTSO *,CurrentTSO,REG_CurrentTSO)
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#define CurrentTSO (BaseReg->rCurrentTSO)
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#if defined(REG_CurrentNursery) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(bdescr *,CurrentNursery,REG_CurrentNursery)
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#define CurrentNursery (BaseReg->rCurrentNursery)
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#if defined(REG_HpAlloc) && !defined(NO_GLOBAL_REG_DECLS)
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GLOBAL_REG_DECL(bdescr *,HpAlloc,REG_HpAlloc)
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#define HpAlloc (BaseReg->rHpAlloc)
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/* -----------------------------------------------------------------------------
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Get absolute function pointers from the register table, to save
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as long as the offset is within the range of a signed byte
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(-128..+127). So we pick some common absolute_addresses and put
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them in the register table. As a bonus, linking time should also
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Other possible candidates in order of importance:
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stg_CAF_BLACKHOLE_info
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anything else probably isn't worth the effort.
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-------------------------------------------------------------------------- */
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#define FunReg ((StgFunTable *)((void *)BaseReg - STG_FIELD_OFFSET(struct PartCapability_, r)))
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#define stg_EAGER_BLACKHOLE_info (FunReg->stgEagerBlackholeInfo)
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#define stg_gc_enter_1 (FunReg->stgGCEnter1)
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#define stg_gc_fun (FunReg->stgGCFun)
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/* -----------------------------------------------------------------------------
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For any registers which are denoted "caller-saves" by the C calling
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convention, we have to emit code to save and restore them across C
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-------------------------------------------------------------------------- */
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#ifdef CALLER_SAVES_R1
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#define CALLER_SAVE_R1 SAVE_R1 = R1;
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#define CALLER_RESTORE_R1 R1 = SAVE_R1;
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#define CALLER_SAVE_R1 /* nothing */
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#define CALLER_RESTORE_R1 /* nothing */
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#ifdef CALLER_SAVES_R2
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#define CALLER_SAVE_R2 SAVE_R2 = R2;
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#define CALLER_RESTORE_R2 R2 = SAVE_R2;
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#define CALLER_SAVE_R2 /* nothing */
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#define CALLER_RESTORE_R2 /* nothing */
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#ifdef CALLER_SAVES_R3
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#define CALLER_SAVE_R3 SAVE_R3 = R3;
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#define CALLER_RESTORE_R3 R3 = SAVE_R3;
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#define CALLER_SAVE_R3 /* nothing */
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#define CALLER_RESTORE_R3 /* nothing */
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#ifdef CALLER_SAVES_R4
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#define CALLER_SAVE_R4 SAVE_R4 = R4;
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#define CALLER_RESTORE_R4 R4 = SAVE_R4;
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#define CALLER_SAVE_R4 /* nothing */
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#define CALLER_RESTORE_R4 /* nothing */
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#ifdef CALLER_SAVES_R5
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#define CALLER_SAVE_R5 SAVE_R5 = R5;
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#define CALLER_RESTORE_R5 R5 = SAVE_R5;
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#define CALLER_SAVE_R5 /* nothing */
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#define CALLER_RESTORE_R5 /* nothing */
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#ifdef CALLER_SAVES_R6
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#define CALLER_SAVE_R6 SAVE_R6 = R6;
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#define CALLER_RESTORE_R6 R6 = SAVE_R6;
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#define CALLER_SAVE_R6 /* nothing */
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#define CALLER_RESTORE_R6 /* nothing */
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#ifdef CALLER_SAVES_R7
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#define CALLER_SAVE_R7 SAVE_R7 = R7;
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#define CALLER_RESTORE_R7 R7 = SAVE_R7;
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#define CALLER_SAVE_R7 /* nothing */
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#define CALLER_RESTORE_R7 /* nothing */
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#ifdef CALLER_SAVES_R8
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#define CALLER_SAVE_R8 SAVE_R8 = R8;
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#define CALLER_RESTORE_R8 R8 = SAVE_R8;
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#define CALLER_SAVE_R8 /* nothing */
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#define CALLER_RESTORE_R8 /* nothing */
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#ifdef CALLER_SAVES_R9
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#define CALLER_SAVE_R9 SAVE_R9 = R9;
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#define CALLER_RESTORE_R9 R9 = SAVE_R9;
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#define CALLER_SAVE_R9 /* nothing */
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#define CALLER_RESTORE_R9 /* nothing */
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#ifdef CALLER_SAVES_R10
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#define CALLER_SAVE_R10 SAVE_R10 = R10;
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#define CALLER_RESTORE_R10 R10 = SAVE_R10;
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#define CALLER_SAVE_R10 /* nothing */
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#define CALLER_RESTORE_R10 /* nothing */
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#ifdef CALLER_SAVES_F1
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#define CALLER_SAVE_F1 SAVE_F1 = F1;
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#define CALLER_RESTORE_F1 F1 = SAVE_F1;
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#define CALLER_SAVE_F1 /* nothing */
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#define CALLER_RESTORE_F1 /* nothing */
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#ifdef CALLER_SAVES_F2
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#define CALLER_SAVE_F2 SAVE_F2 = F2;
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#define CALLER_RESTORE_F2 F2 = SAVE_F2;
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#define CALLER_SAVE_F2 /* nothing */
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#define CALLER_RESTORE_F2 /* nothing */
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#ifdef CALLER_SAVES_F3
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#define CALLER_SAVE_F3 SAVE_F3 = F3;
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#define CALLER_RESTORE_F3 F3 = SAVE_F3;
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#define CALLER_SAVE_F3 /* nothing */
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#define CALLER_RESTORE_F3 /* nothing */
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#ifdef CALLER_SAVES_F4
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#define CALLER_SAVE_F4 SAVE_F4 = F4;
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#define CALLER_RESTORE_F4 F4 = SAVE_F4;
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#define CALLER_SAVE_F4 /* nothing */
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#define CALLER_RESTORE_F4 /* nothing */
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#ifdef CALLER_SAVES_D1
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#define CALLER_SAVE_D1 SAVE_D1 = D1;
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#define CALLER_RESTORE_D1 D1 = SAVE_D1;
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#define CALLER_SAVE_D1 /* nothing */
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#define CALLER_RESTORE_D1 /* nothing */
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#ifdef CALLER_SAVES_D2
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#define CALLER_SAVE_D2 SAVE_D2 = D2;
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#define CALLER_RESTORE_D2 D2 = SAVE_D2;
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#define CALLER_SAVE_D2 /* nothing */
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#define CALLER_RESTORE_D2 /* nothing */
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#ifdef CALLER_SAVES_L1
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#define CALLER_SAVE_L1 SAVE_L1 = L1;
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#define CALLER_RESTORE_L1 L1 = SAVE_L1;
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#define CALLER_SAVE_L1 /* nothing */
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#define CALLER_RESTORE_L1 /* nothing */
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#ifdef CALLER_SAVES_Sp
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#define CALLER_SAVE_Sp SAVE_Sp = Sp;
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#define CALLER_RESTORE_Sp Sp = SAVE_Sp;
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#define CALLER_SAVE_Sp /* nothing */
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#define CALLER_RESTORE_Sp /* nothing */
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#ifdef CALLER_SAVES_SpLim
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#define CALLER_SAVE_SpLim SAVE_SpLim = SpLim;
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#define CALLER_RESTORE_SpLim SpLim = SAVE_SpLim;
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#define CALLER_SAVE_SpLim /* nothing */
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#define CALLER_RESTORE_SpLim /* nothing */
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#ifdef CALLER_SAVES_Hp
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#define CALLER_SAVE_Hp SAVE_Hp = Hp;
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#define CALLER_RESTORE_Hp Hp = SAVE_Hp;
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#define CALLER_SAVE_Hp /* nothing */
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#define CALLER_RESTORE_Hp /* nothing */
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#ifdef CALLER_SAVES_Base
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#error "Can't have caller-saved BaseReg with THREADED_RTS"
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#define CALLER_SAVE_Base /* nothing */
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#define CALLER_RESTORE_Base BaseReg = &MainRegTable;
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#define CALLER_SAVE_Base /* nothing */
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#define CALLER_RESTORE_Base /* nothing */
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#ifdef CALLER_SAVES_CurrentTSO
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#define CALLER_SAVE_CurrentTSO SAVE_CurrentTSO = CurrentTSO;
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#define CALLER_RESTORE_CurrentTSO CurrentTSO = SAVE_CurrentTSO;
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#define CALLER_SAVE_CurrentTSO /* nothing */
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#define CALLER_RESTORE_CurrentTSO /* nothing */
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#ifdef CALLER_SAVES_CurrentNursery
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#define CALLER_SAVE_CurrentNursery SAVE_CurrentNursery = CurrentNursery;
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#define CALLER_RESTORE_CurrentNursery CurrentNursery = SAVE_CurrentNursery;
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#define CALLER_SAVE_CurrentNursery /* nothing */
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#define CALLER_RESTORE_CurrentNursery /* nothing */
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#ifdef CALLER_SAVES_HpAlloc
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#define CALLER_SAVE_HpAlloc SAVE_HpAlloc = HpAlloc;
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#define CALLER_RESTORE_HpAlloc HpAlloc = SAVE_HpAlloc;
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#define CALLER_SAVE_HpAlloc /* nothing */
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#define CALLER_RESTORE_HpAlloc /* nothing */
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#endif /* IN_STG_CODE */
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/* ----------------------------------------------------------------------------
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Handy bunches of saves/restores
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------------------------------------------------------------------------ */
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#define CALLER_SAVE_USER \
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/* Save Base last, since the others may
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be addressed relative to it */
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#define CALLER_SAVE_SYSTEM \
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CALLER_SAVE_CurrentTSO \
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CALLER_SAVE_CurrentNursery \
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#define CALLER_RESTORE_USER \
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/* Restore Base first, since the others may
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be addressed relative to it */
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#define CALLER_RESTORE_SYSTEM \
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CALLER_RESTORE_Base \
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CALLER_RESTORE_SpLim \
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CALLER_RESTORE_CurrentTSO \
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CALLER_RESTORE_CurrentNursery
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#else /* not IN_STG_CODE */
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#define CALLER_SAVE_USER /* nothing */
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#define CALLER_SAVE_SYSTEM /* nothing */
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#define CALLER_RESTORE_USER /* nothing */
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#define CALLER_RESTORE_SYSTEM /* nothing */
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#endif /* IN_STG_CODE */
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#define CALLER_SAVE_ALL \
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#define CALLER_RESTORE_ALL \
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CALLER_RESTORE_SYSTEM \