src/cmd/compile/internal/ssa/config.go

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package ssa

import (
	"cmd/compile/internal/types"
	"cmd/internal/obj"
	"cmd/internal/objabi"
	"cmd/internal/src"
	"os"
	"strconv"
)

// A Config holds readonly compilation information.
// It is created once, early during compilation,
// and shared across all compilations.
type Config struct {
	arch            string // "amd64", etc.
	PtrSize         int64  // 4 or 8; copy of cmd/internal/sys.Arch.PtrSize
	RegSize         int64  // 4 or 8; copy of cmd/internal/sys.Arch.RegSize
	Types           Types
	lowerBlock      blockRewriter // lowering function
	lowerValue      valueRewriter // lowering function
	registers       []Register    // machine registers
	gpRegMask       regMask       // general purpose integer register mask
	fpRegMask       regMask       // floating point register mask
	specialRegMask  regMask       // special register mask
	FPReg           int8          // register number of frame pointer, -1 if not used
	LinkReg         int8          // register number of link register if it is a general purpose register, -1 if not used
	hasGReg         bool          // has hardware g register
	ctxt            *obj.Link     // Generic arch information
	optimize        bool          // Do optimization
	noDuffDevice    bool          // Don't use Duff's device
	useSSE          bool          // Use SSE for non-float operations
	nacl            bool          // GOOS=nacl
	use387          bool          // GO386=387
	SoftFloat       bool          //
	NeedsFpScratch  bool          // No direct move between GP and FP register sets
	BigEndian       bool          //
	sparsePhiCutoff uint64        // Sparse phi location algorithm used above this #blocks*#variables score
}

type (
	blockRewriter func(*Block) bool
	valueRewriter func(*Value) bool
)

type Types struct {
	Bool       *types.Type
	Int8       *types.Type
	Int16      *types.Type
	Int32      *types.Type
	Int64      *types.Type
	UInt8      *types.Type
	UInt16     *types.Type
	UInt32     *types.Type
	UInt64     *types.Type
	Int        *types.Type
	Float32    *types.Type
	Float64    *types.Type
	UInt       *types.Type
	Uintptr    *types.Type
	String     *types.Type
	BytePtr    *types.Type // TODO: use unsafe.Pointer instead?
	Int32Ptr   *types.Type
	UInt32Ptr  *types.Type
	IntPtr     *types.Type
	UintptrPtr *types.Type
	Float32Ptr *types.Type
	Float64Ptr *types.Type
	BytePtrPtr *types.Type
}

type Logger interface {
	// Logf logs a message from the compiler.
	Logf(string, ...interface{})

	// Log returns true if logging is not a no-op
	// some logging calls account for more than a few heap allocations.
	Log() bool

	// Fatal reports a compiler error and exits.
	Fatalf(pos src.XPos, msg string, args ...interface{})

	// Warnl writes compiler messages in the form expected by "errorcheck" tests
	Warnl(pos src.XPos, fmt_ string, args ...interface{})

	// Forwards the Debug flags from gc
	Debug_checknil() bool
	Debug_eagerwb() bool
}

type Frontend interface {
	CanSSA(t *types.Type) bool

	Logger

	// StringData returns a symbol pointing to the given string's contents.
	StringData(string) interface{} // returns *gc.Sym

	// Auto returns a Node for an auto variable of the given type.
	// The SSA compiler uses this function to allocate space for spills.
	Auto(src.XPos, *types.Type) GCNode

	// Given the name for a compound type, returns the name we should use
	// for the parts of that compound type.
	SplitString(LocalSlot) (LocalSlot, LocalSlot)
	SplitInterface(LocalSlot) (LocalSlot, LocalSlot)
	SplitSlice(LocalSlot) (LocalSlot, LocalSlot, LocalSlot)
	SplitComplex(LocalSlot) (LocalSlot, LocalSlot)
	SplitStruct(LocalSlot, int) LocalSlot
	SplitArray(LocalSlot) LocalSlot              // array must be length 1
	SplitInt64(LocalSlot) (LocalSlot, LocalSlot) // returns (hi, lo)

	// DerefItab dereferences an itab function
	// entry, given the symbol of the itab and
	// the byte offset of the function pointer.
	// It may return nil.
	DerefItab(sym *obj.LSym, offset int64) *obj.LSym

	// Line returns a string describing the given position.
	Line(src.XPos) string

	// AllocFrame assigns frame offsets to all live auto variables.
	AllocFrame(f *Func)

	// Syslook returns a symbol of the runtime function/variable with the
	// given name.
	Syslook(string) *obj.LSym

	// UseWriteBarrier returns whether write barrier is enabled
	UseWriteBarrier() bool

	// SetWBPos indicates that a write barrier has been inserted
	// in this function at position pos.
	SetWBPos(pos src.XPos)
}

// interface used to hold a *gc.Node (a stack variable).
// We'd use *gc.Node directly but that would lead to an import cycle.
type GCNode interface {
	Typ() *types.Type
	String() string
	StorageClass() StorageClass
}

type StorageClass uint8

const (
	ClassAuto     StorageClass = iota // local stack variable
	ClassParam                        // argument
	ClassParamOut                     // return value
)

// NewConfig returns a new configuration object for the given architecture.
func NewConfig(arch string, types Types, ctxt *obj.Link, optimize bool) *Config {
	c := &Config{arch: arch, Types: types}
	switch arch {
	case "amd64":
		c.PtrSize = 8
		c.RegSize = 8
		c.lowerBlock = rewriteBlockAMD64
		c.lowerValue = rewriteValueAMD64
		c.registers = registersAMD64[:]
		c.gpRegMask = gpRegMaskAMD64
		c.fpRegMask = fpRegMaskAMD64
		c.FPReg = framepointerRegAMD64
		c.LinkReg = linkRegAMD64
		c.hasGReg = false
	case "amd64p32":
		c.PtrSize = 4
		c.RegSize = 8
		c.lowerBlock = rewriteBlockAMD64
		c.lowerValue = rewriteValueAMD64
		c.registers = registersAMD64[:]
		c.gpRegMask = gpRegMaskAMD64
		c.fpRegMask = fpRegMaskAMD64
		c.FPReg = framepointerRegAMD64
		c.LinkReg = linkRegAMD64
		c.hasGReg = false
		c.noDuffDevice = true
	case "386":
		c.PtrSize = 4
		c.RegSize = 4
		c.lowerBlock = rewriteBlock386
		c.lowerValue = rewriteValue386
		c.registers = registers386[:]
		c.gpRegMask = gpRegMask386
		c.fpRegMask = fpRegMask386
		c.FPReg = framepointerReg386
		c.LinkReg = linkReg386
		c.hasGReg = false
	case "arm":
		c.PtrSize = 4
		c.RegSize = 4
		c.lowerBlock = rewriteBlockARM
		c.lowerValue = rewriteValueARM
		c.registers = registersARM[:]
		c.gpRegMask = gpRegMaskARM
		c.fpRegMask = fpRegMaskARM
		c.FPReg = framepointerRegARM
		c.LinkReg = linkRegARM
		c.hasGReg = true
	case "arm64":
		c.PtrSize = 8
		c.RegSize = 8
		c.lowerBlock = rewriteBlockARM64
		c.lowerValue = rewriteValueARM64
		c.registers = registersARM64[:]
		c.gpRegMask = gpRegMaskARM64
		c.fpRegMask = fpRegMaskARM64
		c.FPReg = framepointerRegARM64
		c.LinkReg = linkRegARM64
		c.hasGReg = true
		c.noDuffDevice = objabi.GOOS == "darwin" // darwin linker cannot handle BR26 reloc with non-zero addend
	case "ppc64":
		c.BigEndian = true
		fallthrough
	case "ppc64le":
		c.PtrSize = 8
		c.RegSize = 8
		c.lowerBlock = rewriteBlockPPC64
		c.lowerValue = rewriteValuePPC64
		c.registers = registersPPC64[:]
		c.gpRegMask = gpRegMaskPPC64
		c.fpRegMask = fpRegMaskPPC64
		c.FPReg = framepointerRegPPC64
		c.LinkReg = linkRegPPC64
		c.noDuffDevice = true // TODO: Resolve PPC64 DuffDevice (has zero, but not copy)
		c.hasGReg = true
	case "mips64":
		c.BigEndian = true
		fallthrough
	case "mips64le":
		c.PtrSize = 8
		c.RegSize = 8
		c.lowerBlock = rewriteBlockMIPS64
		c.lowerValue = rewriteValueMIPS64
		c.registers = registersMIPS64[:]
		c.gpRegMask = gpRegMaskMIPS64
		c.fpRegMask = fpRegMaskMIPS64
		c.specialRegMask = specialRegMaskMIPS64
		c.FPReg = framepointerRegMIPS64
		c.LinkReg = linkRegMIPS64
		c.hasGReg = true
	case "s390x":
		c.PtrSize = 8
		c.RegSize = 8
		c.lowerBlock = rewriteBlockS390X
		c.lowerValue = rewriteValueS390X
		c.registers = registersS390X[:]
		c.gpRegMask = gpRegMaskS390X
		c.fpRegMask = fpRegMaskS390X
		c.FPReg = framepointerRegS390X
		c.LinkReg = linkRegS390X
		c.hasGReg = true
		c.noDuffDevice = true
		c.BigEndian = true
	case "mips":
		c.BigEndian = true
		fallthrough
	case "mipsle":
		c.PtrSize = 4
		c.RegSize = 4
		c.lowerBlock = rewriteBlockMIPS
		c.lowerValue = rewriteValueMIPS
		c.registers = registersMIPS[:]
		c.gpRegMask = gpRegMaskMIPS
		c.fpRegMask = fpRegMaskMIPS
		c.specialRegMask = specialRegMaskMIPS
		c.FPReg = framepointerRegMIPS
		c.LinkReg = linkRegMIPS
		c.hasGReg = true
		c.noDuffDevice = true
	default:
		ctxt.Diag("arch %s not implemented", arch)
	}
	c.ctxt = ctxt
	c.optimize = optimize
	c.nacl = objabi.GOOS == "nacl"
	c.useSSE = true

	// Don't use Duff's device nor SSE on Plan 9 AMD64, because
	// floating point operations are not allowed in note handler.
	if objabi.GOOS == "plan9" && arch == "amd64" {
		c.noDuffDevice = true
		c.useSSE = false
	}

	if c.nacl {
		c.noDuffDevice = true // Don't use Duff's device on NaCl

		// runtime call clobber R12 on nacl
		opcodeTable[OpARMCALLudiv].reg.clobbers |= 1 << 12 // R12
	}

	// cutoff is compared with product of numblocks and numvalues,
	// if product is smaller than cutoff, use old non-sparse method.
	// cutoff == 0 implies all sparse.
	// cutoff == -1 implies none sparse.
	// Good cutoff values seem to be O(million) depending on constant factor cost of sparse.
	// TODO: get this from a flag, not an environment variable
	c.sparsePhiCutoff = 2500000 // 0 for testing. // 2500000 determined with crude experiments w/ make.bash
	ev := os.Getenv("GO_SSA_PHI_LOC_CUTOFF")
	if ev != "" {
		v, err := strconv.ParseInt(ev, 10, 64)
		if err != nil {
			ctxt.Diag("Environment variable GO_SSA_PHI_LOC_CUTOFF (value '%s') did not parse as a number", ev)
		}
		c.sparsePhiCutoff = uint64(v) // convert -1 to maxint, for never use sparse
	}

	return c
}

func (c *Config) Set387(b bool) {
	c.NeedsFpScratch = b
	c.use387 = b
}

func (c *Config) SparsePhiCutoff() uint64 { return c.sparsePhiCutoff }
func (c *Config) Ctxt() *obj.Link         { return c.ctxt }