GHC.CmmToAsm

Note [Native code generator] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The native-code generator has machine-independent and machine-dependent modules.

This module (GHC.CmmToAsm) is the top-level machine-independent module. Before entering machine-dependent land, we do some machine-independent optimisations (defined below) on the CmmStmtss. (Which ideally would be folded into CmmOpt ...)

We convert to the machine-specific Instr datatype with cmmCodeGen, assuming an infinite supply of registers. We then use a (mostly) machine-independent register allocator to rejoin reality. Obviously, regAlloc has machine-specific helper functions (see the used register allocator for details).

Finally, we order the basic blocks of the function so as to minimise the number of jumps between blocks, by utilising fallthrough wherever possible.

The machine-dependent bits are generally contained under GHCCmmToAsmArch/* and generally breaks down as follows:

• Regs: Everything about the target platform's machine registers (and immediate operands, and addresses, which tend to intermingle/interact with registers).
• Instr: Includes the Instr datatype plus a miscellany of other things (e.g., targetDoubleSize, smStablePtrTable, ...)
• CodeGen: is where Cmm stuff turns into machine instructions.
• Ppr: pprInstr turns an Instr into text (well, really a SDoc).

The register allocators lives under GHC.CmmToAsm.Reg.*, there is both a Linear and a Graph based register allocator. Both of which have their own notes describing them. They are mostly platform independent but there are some platform specific files encoding architecture details under RegAllocatorArch.hs

• }

Documentation

nativeCodeGen :: Logger -> ToolSettings -> NCGConfig -> ModLocation -> Handle -> UniqSupply -> Stream IO RawCmmGroup a -> IO a

Test-only exports: see #12744

cmmNativeGen

Arguments

:: forall statics instr jumpDest. (Instruction instr, OutputableP Platform statics, Outputable jumpDest)

=> Logger

-> NcgImpl statics instr jumpDest

-> UniqSupply

-> DwarfFiles

-> LabelMap DebugBlock

-> RawCmmDecl

the cmm to generate code for

-> Int

sequence number of this top thing

-> IO (UniqSupply, DwarfFiles, [NatCmmDecl statics instr], [CLabel], Maybe [RegAllocStats statics instr], Maybe [RegAllocStats], LabelMap [UnwindPoint])

Complete native code generation phase for a single top-level chunk of Cmm. Dumping the output of each stage along the way. Global conflict graph and NGC stats

data NcgImpl statics instr jumpDest

Constructors

NcgImpl

Fields

• ncgConfig :: !NCGConfig
• cmmTopCodeGen :: RawCmmDecl -> NatM [NatCmmDecl statics instr]
• generateJumpTableForInstr :: instr -> Maybe (NatCmmDecl statics instr)
• getJumpDestBlockId :: jumpDest -> Maybe BlockId
• canShortcut :: instr -> Maybe jumpDest
• shortcutStatics :: (BlockId -> Maybe jumpDest) -> statics -> statics
• shortcutJump :: (BlockId -> Maybe jumpDest) -> instr -> instr
• pprNatCmmDeclS :: NatCmmDecl statics instr -> SDoc

  Module is only for printing internal labels. See Note [Internal proc labels] in CLabel.

• pprNatCmmDeclH :: NatCmmDecl statics instr -> HDoc
• maxSpillSlots :: Int
• allocatableRegs :: [RealReg]
• ncgAllocMoreStack :: Int -> NatCmmDecl statics instr -> UniqSM (NatCmmDecl statics instr, [(BlockId, BlockId)])

  The list of block ids records the redirected jumps to allow us to update the CFG.

• ncgMakeFarBranches :: Platform -> LabelMap RawCmmStatics -> [NatBasicBlock instr] -> UniqSM [NatBasicBlock instr]
• extractUnwindPoints :: [instr] -> [UnwindPoint]

  given the instruction sequence of a block, produce a list of the block's UnwindPoints See Note [What is this unwinding business?] in GHC.Cmm.DebugBlock and Note [Unwinding information in the NCG] in this module.

• invertCondBranches :: Maybe CFG -> LabelMap RawCmmStatics -> [NatBasicBlock instr] -> [NatBasicBlock instr]

  Turn the sequence of jcc l1; jmp l2 into jncc l2; <block_l1> when possible.