1 -----------------------------------------------------------------------------
5 -- (c) The University of Glasgow 2004-2006
7 -----------------------------------------------------------------------------
11 GenCmmTop(..), CmmTop,
12 GenBasicBlock(..), CmmBasicBlock, blockId, blockStmts,
13 CmmStmt(..), CmmActuals, CmmFormals,
15 CmmStatic(..), Section(..),
16 CmmExpr(..), cmmExprRep,
17 CmmReg(..), cmmRegRep,
18 CmmLit(..), cmmLitRep,
19 LocalReg(..), localRegRep,
20 BlockId(..), BlockEnv,
21 GlobalReg(..), globalRegRep,
23 node, nodeReg, spReg, hpReg, spLimReg
26 #include "HsVersions.h"
37 -----------------------------------------------------------------------------
38 -- Cmm, CmmTop, CmmBasicBlock
39 -----------------------------------------------------------------------------
41 -- A file is a list of top-level chunks. These may be arbitrarily
42 -- re-orderd during code generation.
44 -- GenCmm is abstracted over
45 -- (a) the type of static data elements
46 -- (b) the contents of a basic block.
47 -- We expect there to be two main instances of this type:
48 -- (a) Plain C--, i.e. populated with CmmLit and CmmExpr respectively,
49 -- (b) Native code, populated with instructions
51 newtype GenCmm d i = Cmm [GenCmmTop d i]
53 type Cmm = GenCmm CmmStatic CmmStmt
55 -- A top-level chunk, abstracted over the type of the contents of
56 -- the basic blocks (Cmm or instructions are the likely instantiations).
59 [d] -- Info table, may be empty
60 CLabel -- Used to generate both info & entry labels
61 [LocalReg] -- Argument locals live on entry (C-- procedure params)
62 [GenBasicBlock i] -- Code, may be empty. The first block is
63 -- the entry point. The order is otherwise initially
64 -- unimportant, but at some point the code gen will
67 -- the BlockId of the first block does not give rise
68 -- to a label. To jump to the first block in a Proc,
69 -- use the appropriate CLabel.
72 | CmmData Section [d] -- constant values only
74 type CmmTop = GenCmmTop CmmStatic CmmStmt
76 -- A basic block containing a single label, at the beginning.
77 -- The list of basic blocks in a top-level code block may be re-ordered.
78 -- Fall-through is not allowed: there must be an explicit jump at the
79 -- end of each basic block, but the code generator might rearrange basic
80 -- blocks in order to turn some jumps into fallthroughs.
82 data GenBasicBlock i = BasicBlock BlockId [i]
83 -- ToDo: Julian suggests that we might need to annotate this type
84 -- with the out & in edges in the graph, i.e. two * [BlockId]. This
85 -- information can be derived from the contents, but it might be
86 -- helpful to cache it here.
88 type CmmBasicBlock = GenBasicBlock CmmStmt
90 blockId :: GenBasicBlock i -> BlockId
91 -- The branch block id is that of the first block in
92 -- the branch, which is that branch's entry point
93 blockId (BasicBlock blk_id _ ) = blk_id
95 blockStmts :: GenBasicBlock i -> [i]
96 blockStmts (BasicBlock _ stmts) = stmts
99 -----------------------------------------------------------------------------
101 -- A "statement". Note that all branches are explicit: there are no
102 -- control transfers to computed addresses, except when transfering
103 -- control to a new function.
104 -----------------------------------------------------------------------------
108 | CmmComment FastString
110 | CmmAssign CmmReg CmmExpr -- Assign to register
112 | CmmStore CmmExpr CmmExpr -- Assign to memory location. Size is
113 -- given by cmmExprRep of the rhs.
115 | CmmCall -- A foreign call, with
117 CmmFormals -- zero or more results
118 CmmActuals -- zero or more arguments
119 (Maybe [GlobalReg]) -- Global regs that may need to be saved
120 -- if they will be clobbered by the call.
121 -- Nothing <=> save *all* globals that
122 -- might be clobbered.
124 | CmmBranch BlockId -- branch to another BB in this fn
126 | CmmCondBranch CmmExpr BlockId -- conditional branch
128 | CmmSwitch CmmExpr [Maybe BlockId] -- Table branch
129 -- The scrutinee is zero-based;
130 -- zero -> first block
131 -- one -> second block etc
132 -- Undefined outside range, and when there's a Nothing
134 | CmmJump CmmExpr -- Jump to another function,
135 CmmActuals -- with these parameters.
137 | CmmReturn -- Return from a function,
138 CmmActuals -- with these return values.
140 type CmmActuals = [(CmmExpr,MachHint)]
141 type CmmFormals = [(CmmReg,MachHint)]
147 One possible problem with the above type is that the only way to do a
148 non-local conditional jump is to encode it as a branch to a block that
149 contains a single jump. This leads to inefficient code in the back end.
151 One possible way to fix this would be:
155 | CmmJump CmmBranchDest
156 | CmmCondJump CmmExpr CmmBranchDest
161 | NonLocal CmmExpr [LocalReg]
165 + one fewer constructors in CmmStmt
166 + allows both cond branch and switch to jump to non-local destinations
170 - not strictly necessary: can already encode as branch+jump
171 - not always possible to implement any better in the back end
172 - could do the optimisation in the back end (but then plat-specific?)
173 - C-- doesn't have it
174 - back-end optimisation might be more general (jump shortcutting)
176 So we'll stick with the way it is, and add the optimisation to the NCG.
179 -----------------------------------------------------------------------------
182 -- The target of a CmmCall.
183 -----------------------------------------------------------------------------
186 = CmmForeignCall -- Call to a foreign function
187 CmmExpr -- literal label <=> static call
188 -- other expression <=> dynamic call
189 CCallConv -- The calling convention
191 | CmmPrim -- Call to a "primitive" (eg. sin, cos)
192 CallishMachOp -- These might be implemented as inline
193 -- code by the backend.
195 -----------------------------------------------------------------------------
197 -- An expression. Expressions have no side effects.
198 -----------------------------------------------------------------------------
201 = CmmLit CmmLit -- Literal
202 | CmmLoad CmmExpr MachRep -- Read memory location
203 | CmmReg CmmReg -- Contents of register
204 | CmmMachOp MachOp [CmmExpr] -- Machine operation (+, -, *, etc.)
205 | CmmRegOff CmmReg Int
207 -- ** is shorthand only, meaning **
208 -- CmmMachOp (MO_S_Add rep (CmmReg reg) (CmmLit (CmmInt i rep)))
209 -- where rep = cmmRegRep reg
212 cmmExprRep :: CmmExpr -> MachRep
213 cmmExprRep (CmmLit lit) = cmmLitRep lit
214 cmmExprRep (CmmLoad _ rep) = rep
215 cmmExprRep (CmmReg reg) = cmmRegRep reg
216 cmmExprRep (CmmMachOp op _) = resultRepOfMachOp op
217 cmmExprRep (CmmRegOff reg _) = cmmRegRep reg
221 | CmmGlobal GlobalReg
224 cmmRegRep :: CmmReg -> MachRep
225 cmmRegRep (CmmLocal reg) = localRegRep reg
226 cmmRegRep (CmmGlobal reg) = globalRegRep reg
229 = LocalReg !Unique MachRep
231 instance Eq LocalReg where
232 (LocalReg u1 _) == (LocalReg u2 _) = u1 == u2
234 instance Uniquable LocalReg where
235 getUnique (LocalReg uniq _) = uniq
237 localRegRep :: LocalReg -> MachRep
238 localRegRep (LocalReg _ rep) = rep
241 = CmmInt Integer MachRep
242 -- Interpretation: the 2's complement representation of the value
243 -- is truncated to the specified size. This is easier than trying
244 -- to keep the value within range, because we don't know whether
245 -- it will be used as a signed or unsigned value (the MachRep doesn't
246 -- distinguish between signed & unsigned).
247 | CmmFloat Rational MachRep
248 | CmmLabel CLabel -- Address of label
249 | CmmLabelOff CLabel Int -- Address of label + byte offset
251 -- Due to limitations in the C backend, the following
252 -- MUST ONLY be used inside the info table indicated by label2
253 -- (label2 must be the info label), and label1 must be an
254 -- SRT, a slow entrypoint or a large bitmap (see the Mangler)
255 -- Don't use it at all unless tablesNextToCode.
256 -- It is also used inside the NCG during when generating
257 -- position-independent code.
258 | CmmLabelDiffOff CLabel CLabel Int -- label1 - label2 + offset
261 cmmLitRep :: CmmLit -> MachRep
262 cmmLitRep (CmmInt _ rep) = rep
263 cmmLitRep (CmmFloat _ rep) = rep
264 cmmLitRep (CmmLabel _) = wordRep
265 cmmLitRep (CmmLabelOff _ _) = wordRep
266 cmmLitRep (CmmLabelDiffOff _ _ _) = wordRep
268 -----------------------------------------------------------------------------
271 -- Local labels must be unique within a single compilation unit.
273 newtype BlockId = BlockId Unique
276 instance Uniquable BlockId where
277 getUnique (BlockId u) = u
279 type BlockEnv a = UniqFM {- BlockId -} a
281 -----------------------------------------------------------------------------
283 -----------------------------------------------------------------------------
289 | RelocatableReadOnlyData
291 | ReadOnlyData16 -- .rodata.cst16 on x86_64, 16-byte aligned
292 | OtherSection String
295 = CmmStaticLit CmmLit
296 -- a literal value, size given by cmmLitRep of the literal.
297 | CmmUninitialised Int
298 -- uninitialised data, N bytes long
300 -- align to next N-byte boundary (N must be a power of 2).
301 | CmmDataLabel CLabel
302 -- label the current position in this section.
304 -- string of 8-bit values only, not zero terminated.
306 -----------------------------------------------------------------------------
307 -- Global STG registers
308 -----------------------------------------------------------------------------
311 -- Argument and return registers
312 = VanillaReg -- pointers, unboxed ints and chars
313 {-# UNPACK #-} !Int -- its number
315 | FloatReg -- single-precision floating-point registers
316 {-# UNPACK #-} !Int -- its number
318 | DoubleReg -- double-precision floating-point registers
319 {-# UNPACK #-} !Int -- its number
321 | LongReg -- long int registers (64-bit, really)
322 {-# UNPACK #-} !Int -- its number
325 | Sp -- Stack ptr; points to last occupied stack location.
326 | SpLim -- Stack limit
327 | Hp -- Heap ptr; points to last occupied heap location.
328 | HpLim -- Heap limit register
329 | CurrentTSO -- pointer to current thread's TSO
330 | CurrentNursery -- pointer to allocation area
331 | HpAlloc -- allocation count for heap check failure
333 -- We keep the address of some commonly-called
334 -- functions in the register table, to keep code
336 | GCEnter1 -- stg_gc_enter_1
337 | GCFun -- stg_gc_fun
339 -- Base offset for the register table, used for accessing registers
340 -- which do not have real registers assigned to them. This register
341 -- will only appear after we have expanded GlobalReg into memory accesses
342 -- (where necessary) in the native code generator.
345 -- Base Register for PIC (position-independent code) calculations
346 -- Only used inside the native code generator. It's exact meaning differs
347 -- from platform to platform (see module PositionIndependentCode).
356 -- convenient aliases
357 spReg, hpReg, spLimReg, nodeReg :: CmmReg
360 spLimReg = CmmGlobal SpLim
361 nodeReg = CmmGlobal node
366 globalRegRep :: GlobalReg -> MachRep
367 globalRegRep (VanillaReg _) = wordRep
368 globalRegRep (FloatReg _) = F32
369 globalRegRep (DoubleReg _) = F64
370 globalRegRep (LongReg _) = I64
371 globalRegRep _ = wordRep