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ssa.go
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ssa.go
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// 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 ssagen
import (
"bufio"
"bytes"
"cmd/compile/internal/abi"
"fmt"
"go/constant"
"html"
"internal/buildcfg"
"os"
"path/filepath"
"sort"
"strings"
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"cmd/compile/internal/liveness"
"cmd/compile/internal/objw"
"cmd/compile/internal/reflectdata"
"cmd/compile/internal/ssa"
"cmd/compile/internal/staticdata"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/obj"
"cmd/internal/obj/x86"
"cmd/internal/objabi"
"cmd/internal/src"
"cmd/internal/sys"
)
var ssaConfig *ssa.Config
var ssaCaches []ssa.Cache
var ssaDump string // early copy of $GOSSAFUNC; the func name to dump output for
var ssaDir string // optional destination for ssa dump file
var ssaDumpStdout bool // whether to dump to stdout
var ssaDumpCFG string // generate CFGs for these phases
const ssaDumpFile = "ssa.html"
// ssaDumpInlined holds all inlined functions when ssaDump contains a function name.
var ssaDumpInlined []*ir.Func
func DumpInline(fn *ir.Func) {
if ssaDump != "" && ssaDump == ir.FuncName(fn) {
ssaDumpInlined = append(ssaDumpInlined, fn)
}
}
func InitEnv() {
ssaDump = os.Getenv("GOSSAFUNC")
ssaDir = os.Getenv("GOSSADIR")
if ssaDump != "" {
if strings.HasSuffix(ssaDump, "+") {
ssaDump = ssaDump[:len(ssaDump)-1]
ssaDumpStdout = true
}
spl := strings.Split(ssaDump, ":")
if len(spl) > 1 {
ssaDump = spl[0]
ssaDumpCFG = spl[1]
}
}
}
func InitConfig() {
types_ := ssa.NewTypes()
if Arch.SoftFloat {
softfloatInit()
}
// Generate a few pointer types that are uncommon in the frontend but common in the backend.
// Caching is disabled in the backend, so generating these here avoids allocations.
_ = types.NewPtr(types.Types[types.TINTER]) // *interface{}
_ = types.NewPtr(types.NewPtr(types.Types[types.TSTRING])) // **string
_ = types.NewPtr(types.NewSlice(types.Types[types.TINTER])) // *[]interface{}
_ = types.NewPtr(types.NewPtr(types.ByteType)) // **byte
_ = types.NewPtr(types.NewSlice(types.ByteType)) // *[]byte
_ = types.NewPtr(types.NewSlice(types.Types[types.TSTRING])) // *[]string
_ = types.NewPtr(types.NewPtr(types.NewPtr(types.Types[types.TUINT8]))) // ***uint8
_ = types.NewPtr(types.Types[types.TINT16]) // *int16
_ = types.NewPtr(types.Types[types.TINT64]) // *int64
_ = types.NewPtr(types.ErrorType) // *error
types.NewPtrCacheEnabled = false
ssaConfig = ssa.NewConfig(base.Ctxt.Arch.Name, *types_, base.Ctxt, base.Flag.N == 0, Arch.SoftFloat)
ssaConfig.Race = base.Flag.Race
ssaCaches = make([]ssa.Cache, base.Flag.LowerC)
// Set up some runtime functions we'll need to call.
ir.Syms.AssertE2I = typecheck.LookupRuntimeFunc("assertE2I")
ir.Syms.AssertE2I2 = typecheck.LookupRuntimeFunc("assertE2I2")
ir.Syms.AssertI2I = typecheck.LookupRuntimeFunc("assertI2I")
ir.Syms.AssertI2I2 = typecheck.LookupRuntimeFunc("assertI2I2")
ir.Syms.CheckPtrAlignment = typecheck.LookupRuntimeFunc("checkptrAlignment")
ir.Syms.Deferproc = typecheck.LookupRuntimeFunc("deferproc")
ir.Syms.DeferprocStack = typecheck.LookupRuntimeFunc("deferprocStack")
ir.Syms.Deferreturn = typecheck.LookupRuntimeFunc("deferreturn")
ir.Syms.Duffcopy = typecheck.LookupRuntimeFunc("duffcopy")
ir.Syms.Duffzero = typecheck.LookupRuntimeFunc("duffzero")
ir.Syms.GCWriteBarrier = typecheck.LookupRuntimeFunc("gcWriteBarrier")
ir.Syms.Goschedguarded = typecheck.LookupRuntimeFunc("goschedguarded")
ir.Syms.Growslice = typecheck.LookupRuntimeFunc("growslice")
ir.Syms.Msanread = typecheck.LookupRuntimeFunc("msanread")
ir.Syms.Msanwrite = typecheck.LookupRuntimeFunc("msanwrite")
ir.Syms.Msanmove = typecheck.LookupRuntimeFunc("msanmove")
ir.Syms.Asanread = typecheck.LookupRuntimeFunc("asanread")
ir.Syms.Asanwrite = typecheck.LookupRuntimeFunc("asanwrite")
ir.Syms.Newobject = typecheck.LookupRuntimeFunc("newobject")
ir.Syms.Newproc = typecheck.LookupRuntimeFunc("newproc")
ir.Syms.Panicdivide = typecheck.LookupRuntimeFunc("panicdivide")
ir.Syms.PanicdottypeE = typecheck.LookupRuntimeFunc("panicdottypeE")
ir.Syms.PanicdottypeI = typecheck.LookupRuntimeFunc("panicdottypeI")
ir.Syms.Panicnildottype = typecheck.LookupRuntimeFunc("panicnildottype")
ir.Syms.Panicoverflow = typecheck.LookupRuntimeFunc("panicoverflow")
ir.Syms.Panicshift = typecheck.LookupRuntimeFunc("panicshift")
ir.Syms.Raceread = typecheck.LookupRuntimeFunc("raceread")
ir.Syms.Racereadrange = typecheck.LookupRuntimeFunc("racereadrange")
ir.Syms.Racewrite = typecheck.LookupRuntimeFunc("racewrite")
ir.Syms.Racewriterange = typecheck.LookupRuntimeFunc("racewriterange")
ir.Syms.X86HasPOPCNT = typecheck.LookupRuntimeVar("x86HasPOPCNT") // bool
ir.Syms.X86HasSSE41 = typecheck.LookupRuntimeVar("x86HasSSE41") // bool
ir.Syms.X86HasFMA = typecheck.LookupRuntimeVar("x86HasFMA") // bool
ir.Syms.ARMHasVFPv4 = typecheck.LookupRuntimeVar("armHasVFPv4") // bool
ir.Syms.ARM64HasATOMICS = typecheck.LookupRuntimeVar("arm64HasATOMICS") // bool
ir.Syms.Staticuint64s = typecheck.LookupRuntimeVar("staticuint64s")
ir.Syms.Typedmemclr = typecheck.LookupRuntimeFunc("typedmemclr")
ir.Syms.Typedmemmove = typecheck.LookupRuntimeFunc("typedmemmove")
ir.Syms.Udiv = typecheck.LookupRuntimeVar("udiv") // asm func with special ABI
ir.Syms.WriteBarrier = typecheck.LookupRuntimeVar("writeBarrier") // struct { bool; ... }
ir.Syms.Zerobase = typecheck.LookupRuntimeVar("zerobase")
// asm funcs with special ABI
if base.Ctxt.Arch.Name == "amd64" {
GCWriteBarrierReg = map[int16]*obj.LSym{
x86.REG_AX: typecheck.LookupRuntimeFunc("gcWriteBarrier"),
x86.REG_CX: typecheck.LookupRuntimeFunc("gcWriteBarrierCX"),
x86.REG_DX: typecheck.LookupRuntimeFunc("gcWriteBarrierDX"),
x86.REG_BX: typecheck.LookupRuntimeFunc("gcWriteBarrierBX"),
x86.REG_BP: typecheck.LookupRuntimeFunc("gcWriteBarrierBP"),
x86.REG_SI: typecheck.LookupRuntimeFunc("gcWriteBarrierSI"),
x86.REG_R8: typecheck.LookupRuntimeFunc("gcWriteBarrierR8"),
x86.REG_R9: typecheck.LookupRuntimeFunc("gcWriteBarrierR9"),
}
}
if Arch.LinkArch.Family == sys.Wasm {
BoundsCheckFunc[ssa.BoundsIndex] = typecheck.LookupRuntimeFunc("goPanicIndex")
BoundsCheckFunc[ssa.BoundsIndexU] = typecheck.LookupRuntimeFunc("goPanicIndexU")
BoundsCheckFunc[ssa.BoundsSliceAlen] = typecheck.LookupRuntimeFunc("goPanicSliceAlen")
BoundsCheckFunc[ssa.BoundsSliceAlenU] = typecheck.LookupRuntimeFunc("goPanicSliceAlenU")
BoundsCheckFunc[ssa.BoundsSliceAcap] = typecheck.LookupRuntimeFunc("goPanicSliceAcap")
BoundsCheckFunc[ssa.BoundsSliceAcapU] = typecheck.LookupRuntimeFunc("goPanicSliceAcapU")
BoundsCheckFunc[ssa.BoundsSliceB] = typecheck.LookupRuntimeFunc("goPanicSliceB")
BoundsCheckFunc[ssa.BoundsSliceBU] = typecheck.LookupRuntimeFunc("goPanicSliceBU")
BoundsCheckFunc[ssa.BoundsSlice3Alen] = typecheck.LookupRuntimeFunc("goPanicSlice3Alen")
BoundsCheckFunc[ssa.BoundsSlice3AlenU] = typecheck.LookupRuntimeFunc("goPanicSlice3AlenU")
BoundsCheckFunc[ssa.BoundsSlice3Acap] = typecheck.LookupRuntimeFunc("goPanicSlice3Acap")
BoundsCheckFunc[ssa.BoundsSlice3AcapU] = typecheck.LookupRuntimeFunc("goPanicSlice3AcapU")
BoundsCheckFunc[ssa.BoundsSlice3B] = typecheck.LookupRuntimeFunc("goPanicSlice3B")
BoundsCheckFunc[ssa.BoundsSlice3BU] = typecheck.LookupRuntimeFunc("goPanicSlice3BU")
BoundsCheckFunc[ssa.BoundsSlice3C] = typecheck.LookupRuntimeFunc("goPanicSlice3C")
BoundsCheckFunc[ssa.BoundsSlice3CU] = typecheck.LookupRuntimeFunc("goPanicSlice3CU")
BoundsCheckFunc[ssa.BoundsConvert] = typecheck.LookupRuntimeFunc("goPanicSliceConvert")
} else {
BoundsCheckFunc[ssa.BoundsIndex] = typecheck.LookupRuntimeFunc("panicIndex")
BoundsCheckFunc[ssa.BoundsIndexU] = typecheck.LookupRuntimeFunc("panicIndexU")
BoundsCheckFunc[ssa.BoundsSliceAlen] = typecheck.LookupRuntimeFunc("panicSliceAlen")
BoundsCheckFunc[ssa.BoundsSliceAlenU] = typecheck.LookupRuntimeFunc("panicSliceAlenU")
BoundsCheckFunc[ssa.BoundsSliceAcap] = typecheck.LookupRuntimeFunc("panicSliceAcap")
BoundsCheckFunc[ssa.BoundsSliceAcapU] = typecheck.LookupRuntimeFunc("panicSliceAcapU")
BoundsCheckFunc[ssa.BoundsSliceB] = typecheck.LookupRuntimeFunc("panicSliceB")
BoundsCheckFunc[ssa.BoundsSliceBU] = typecheck.LookupRuntimeFunc("panicSliceBU")
BoundsCheckFunc[ssa.BoundsSlice3Alen] = typecheck.LookupRuntimeFunc("panicSlice3Alen")
BoundsCheckFunc[ssa.BoundsSlice3AlenU] = typecheck.LookupRuntimeFunc("panicSlice3AlenU")
BoundsCheckFunc[ssa.BoundsSlice3Acap] = typecheck.LookupRuntimeFunc("panicSlice3Acap")
BoundsCheckFunc[ssa.BoundsSlice3AcapU] = typecheck.LookupRuntimeFunc("panicSlice3AcapU")
BoundsCheckFunc[ssa.BoundsSlice3B] = typecheck.LookupRuntimeFunc("panicSlice3B")
BoundsCheckFunc[ssa.BoundsSlice3BU] = typecheck.LookupRuntimeFunc("panicSlice3BU")
BoundsCheckFunc[ssa.BoundsSlice3C] = typecheck.LookupRuntimeFunc("panicSlice3C")
BoundsCheckFunc[ssa.BoundsSlice3CU] = typecheck.LookupRuntimeFunc("panicSlice3CU")
BoundsCheckFunc[ssa.BoundsConvert] = typecheck.LookupRuntimeFunc("panicSliceConvert")
}
if Arch.LinkArch.PtrSize == 4 {
ExtendCheckFunc[ssa.BoundsIndex] = typecheck.LookupRuntimeVar("panicExtendIndex")
ExtendCheckFunc[ssa.BoundsIndexU] = typecheck.LookupRuntimeVar("panicExtendIndexU")
ExtendCheckFunc[ssa.BoundsSliceAlen] = typecheck.LookupRuntimeVar("panicExtendSliceAlen")
ExtendCheckFunc[ssa.BoundsSliceAlenU] = typecheck.LookupRuntimeVar("panicExtendSliceAlenU")
ExtendCheckFunc[ssa.BoundsSliceAcap] = typecheck.LookupRuntimeVar("panicExtendSliceAcap")
ExtendCheckFunc[ssa.BoundsSliceAcapU] = typecheck.LookupRuntimeVar("panicExtendSliceAcapU")
ExtendCheckFunc[ssa.BoundsSliceB] = typecheck.LookupRuntimeVar("panicExtendSliceB")
ExtendCheckFunc[ssa.BoundsSliceBU] = typecheck.LookupRuntimeVar("panicExtendSliceBU")
ExtendCheckFunc[ssa.BoundsSlice3Alen] = typecheck.LookupRuntimeVar("panicExtendSlice3Alen")
ExtendCheckFunc[ssa.BoundsSlice3AlenU] = typecheck.LookupRuntimeVar("panicExtendSlice3AlenU")
ExtendCheckFunc[ssa.BoundsSlice3Acap] = typecheck.LookupRuntimeVar("panicExtendSlice3Acap")
ExtendCheckFunc[ssa.BoundsSlice3AcapU] = typecheck.LookupRuntimeVar("panicExtendSlice3AcapU")
ExtendCheckFunc[ssa.BoundsSlice3B] = typecheck.LookupRuntimeVar("panicExtendSlice3B")
ExtendCheckFunc[ssa.BoundsSlice3BU] = typecheck.LookupRuntimeVar("panicExtendSlice3BU")
ExtendCheckFunc[ssa.BoundsSlice3C] = typecheck.LookupRuntimeVar("panicExtendSlice3C")
ExtendCheckFunc[ssa.BoundsSlice3CU] = typecheck.LookupRuntimeVar("panicExtendSlice3CU")
}
// Wasm (all asm funcs with special ABIs)
ir.Syms.WasmMove = typecheck.LookupRuntimeVar("wasmMove")
ir.Syms.WasmZero = typecheck.LookupRuntimeVar("wasmZero")
ir.Syms.WasmDiv = typecheck.LookupRuntimeVar("wasmDiv")
ir.Syms.WasmTruncS = typecheck.LookupRuntimeVar("wasmTruncS")
ir.Syms.WasmTruncU = typecheck.LookupRuntimeVar("wasmTruncU")
ir.Syms.SigPanic = typecheck.LookupRuntimeFunc("sigpanic")
}
// AbiForBodylessFuncStackMap returns the ABI for a bodyless function's stack map.
// This is not necessarily the ABI used to call it.
// Currently (1.17 dev) such a stack map is always ABI0;
// any ABI wrapper that is present is nosplit, hence a precise
// stack map is not needed there (the parameters survive only long
// enough to call the wrapped assembly function).
// This always returns a freshly copied ABI.
func AbiForBodylessFuncStackMap(fn *ir.Func) *abi.ABIConfig {
return ssaConfig.ABI0.Copy() // No idea what races will result, be safe
}
// abiForFunc implements ABI policy for a function, but does not return a copy of the ABI.
// Passing a nil function returns the default ABI based on experiment configuration.
func abiForFunc(fn *ir.Func, abi0, abi1 *abi.ABIConfig) *abi.ABIConfig {
if buildcfg.Experiment.RegabiArgs {
// Select the ABI based on the function's defining ABI.
if fn == nil {
return abi1
}
switch fn.ABI {
case obj.ABI0:
return abi0
case obj.ABIInternal:
// TODO(austin): Clean up the nomenclature here.
// It's not clear that "abi1" is ABIInternal.
return abi1
}
base.Fatalf("function %v has unknown ABI %v", fn, fn.ABI)
panic("not reachable")
}
a := abi0
if fn != nil {
if fn.Pragma&ir.RegisterParams != 0 { // TODO(register args) remove after register abi is working
a = abi1
}
}
return a
}
// dvarint writes a varint v to the funcdata in symbol x and returns the new offset
func dvarint(x *obj.LSym, off int, v int64) int {
if v < 0 || v > 1e9 {
panic(fmt.Sprintf("dvarint: bad offset for funcdata - %v", v))
}
if v < 1<<7 {
return objw.Uint8(x, off, uint8(v))
}
off = objw.Uint8(x, off, uint8((v&127)|128))
if v < 1<<14 {
return objw.Uint8(x, off, uint8(v>>7))
}
off = objw.Uint8(x, off, uint8(((v>>7)&127)|128))
if v < 1<<21 {
return objw.Uint8(x, off, uint8(v>>14))
}
off = objw.Uint8(x, off, uint8(((v>>14)&127)|128))
if v < 1<<28 {
return objw.Uint8(x, off, uint8(v>>21))
}
off = objw.Uint8(x, off, uint8(((v>>21)&127)|128))
return objw.Uint8(x, off, uint8(v>>28))
}
// emitOpenDeferInfo emits FUNCDATA information about the defers in a function
// that is using open-coded defers. This funcdata is used to determine the active
// defers in a function and execute those defers during panic processing.
//
// The funcdata is all encoded in varints (since values will almost always be less than
// 128, but stack offsets could potentially be up to 2Gbyte). All "locations" (offsets)
// for stack variables are specified as the number of bytes below varp (pointer to the
// top of the local variables) for their starting address. The format is:
//
// - Offset of the deferBits variable
// - Number of defers in the function
// - Information about each defer call, in reverse order of appearance in the function:
// - Offset of the closure value to call
func (s *state) emitOpenDeferInfo() {
x := base.Ctxt.Lookup(s.curfn.LSym.Name + ".opendefer")
x.Set(obj.AttrContentAddressable, true)
s.curfn.LSym.Func().OpenCodedDeferInfo = x
off := 0
off = dvarint(x, off, -s.deferBitsTemp.FrameOffset())
off = dvarint(x, off, int64(len(s.openDefers)))
// Write in reverse-order, for ease of running in that order at runtime
for i := len(s.openDefers) - 1; i >= 0; i-- {
r := s.openDefers[i]
off = dvarint(x, off, -r.closureNode.FrameOffset())
}
}
func okOffset(offset int64) int64 {
if offset == types.BOGUS_FUNARG_OFFSET {
panic(fmt.Errorf("Bogus offset %d", offset))
}
return offset
}
// buildssa builds an SSA function for fn.
// worker indicates which of the backend workers is doing the processing.
func buildssa(fn *ir.Func, worker int) *ssa.Func {
name := ir.FuncName(fn)
printssa := false
if ssaDump != "" { // match either a simple name e.g. "(*Reader).Reset", package.name e.g. "compress/gzip.(*Reader).Reset", or subpackage name "gzip.(*Reader).Reset"
pkgDotName := base.Ctxt.Pkgpath + "." + name
printssa = name == ssaDump ||
strings.HasSuffix(pkgDotName, ssaDump) && (pkgDotName == ssaDump || strings.HasSuffix(pkgDotName, "/"+ssaDump))
}
var astBuf *bytes.Buffer
if printssa {
astBuf = &bytes.Buffer{}
ir.FDumpList(astBuf, "buildssa-enter", fn.Enter)
ir.FDumpList(astBuf, "buildssa-body", fn.Body)
ir.FDumpList(astBuf, "buildssa-exit", fn.Exit)
if ssaDumpStdout {
fmt.Println("generating SSA for", name)
fmt.Print(astBuf.String())
}
}
var s state
s.pushLine(fn.Pos())
defer s.popLine()
s.hasdefer = fn.HasDefer()
if fn.Pragma&ir.CgoUnsafeArgs != 0 {
s.cgoUnsafeArgs = true
}
s.checkPtrEnabled = ir.ShouldCheckPtr(fn, 1)
fe := ssafn{
curfn: fn,
log: printssa && ssaDumpStdout,
}
s.curfn = fn
s.f = ssa.NewFunc(&fe)
s.config = ssaConfig
s.f.Type = fn.Type()
s.f.Config = ssaConfig
s.f.Cache = &ssaCaches[worker]
s.f.Cache.Reset()
s.f.Name = name
s.f.DebugTest = s.f.DebugHashMatch("GOSSAHASH")
s.f.PrintOrHtmlSSA = printssa
if fn.Pragma&ir.Nosplit != 0 {
s.f.NoSplit = true
}
s.f.ABI0 = ssaConfig.ABI0.Copy() // Make a copy to avoid racy map operations in type-register-width cache.
s.f.ABI1 = ssaConfig.ABI1.Copy()
s.f.ABIDefault = abiForFunc(nil, s.f.ABI0, s.f.ABI1)
s.f.ABISelf = abiForFunc(fn, s.f.ABI0, s.f.ABI1)
s.panics = map[funcLine]*ssa.Block{}
s.softFloat = s.config.SoftFloat
// Allocate starting block
s.f.Entry = s.f.NewBlock(ssa.BlockPlain)
s.f.Entry.Pos = fn.Pos()
if printssa {
ssaDF := ssaDumpFile
if ssaDir != "" {
ssaDF = filepath.Join(ssaDir, base.Ctxt.Pkgpath+"."+name+".html")
ssaD := filepath.Dir(ssaDF)
os.MkdirAll(ssaD, 0755)
}
s.f.HTMLWriter = ssa.NewHTMLWriter(ssaDF, s.f, ssaDumpCFG)
// TODO: generate and print a mapping from nodes to values and blocks
dumpSourcesColumn(s.f.HTMLWriter, fn)
s.f.HTMLWriter.WriteAST("AST", astBuf)
}
// Allocate starting values
s.labels = map[string]*ssaLabel{}
s.fwdVars = map[ir.Node]*ssa.Value{}
s.startmem = s.entryNewValue0(ssa.OpInitMem, types.TypeMem)
s.hasOpenDefers = base.Flag.N == 0 && s.hasdefer && !s.curfn.OpenCodedDeferDisallowed()
switch {
case base.Debug.NoOpenDefer != 0:
s.hasOpenDefers = false
case s.hasOpenDefers && (base.Ctxt.Flag_shared || base.Ctxt.Flag_dynlink) && base.Ctxt.Arch.Name == "386":
// Don't support open-coded defers for 386 ONLY when using shared
// libraries, because there is extra code (added by rewriteToUseGot())
// preceding the deferreturn/ret code that we don't track correctly.
s.hasOpenDefers = false
}
if s.hasOpenDefers && len(s.curfn.Exit) > 0 {
// Skip doing open defers if there is any extra exit code (likely
// race detection), since we will not generate that code in the
// case of the extra deferreturn/ret segment.
s.hasOpenDefers = false
}
if s.hasOpenDefers {
// Similarly, skip if there are any heap-allocated result
// parameters that need to be copied back to their stack slots.
for _, f := range s.curfn.Type().Results().FieldSlice() {
if !f.Nname.(*ir.Name).OnStack() {
s.hasOpenDefers = false
break
}
}
}
if s.hasOpenDefers &&
s.curfn.NumReturns*s.curfn.NumDefers > 15 {
// Since we are generating defer calls at every exit for
// open-coded defers, skip doing open-coded defers if there are
// too many returns (especially if there are multiple defers).
// Open-coded defers are most important for improving performance
// for smaller functions (which don't have many returns).
s.hasOpenDefers = false
}
s.sp = s.entryNewValue0(ssa.OpSP, types.Types[types.TUINTPTR]) // TODO: use generic pointer type (unsafe.Pointer?) instead
s.sb = s.entryNewValue0(ssa.OpSB, types.Types[types.TUINTPTR])
s.startBlock(s.f.Entry)
s.vars[memVar] = s.startmem
if s.hasOpenDefers {
// Create the deferBits variable and stack slot. deferBits is a
// bitmask showing which of the open-coded defers in this function
// have been activated.
deferBitsTemp := typecheck.TempAt(src.NoXPos, s.curfn, types.Types[types.TUINT8])
deferBitsTemp.SetAddrtaken(true)
s.deferBitsTemp = deferBitsTemp
// For this value, AuxInt is initialized to zero by default
startDeferBits := s.entryNewValue0(ssa.OpConst8, types.Types[types.TUINT8])
s.vars[deferBitsVar] = startDeferBits
s.deferBitsAddr = s.addr(deferBitsTemp)
s.store(types.Types[types.TUINT8], s.deferBitsAddr, startDeferBits)
// Make sure that the deferBits stack slot is kept alive (for use
// by panics) and stores to deferBits are not eliminated, even if
// all checking code on deferBits in the function exit can be
// eliminated, because the defer statements were all
// unconditional.
s.vars[memVar] = s.newValue1Apos(ssa.OpVarLive, types.TypeMem, deferBitsTemp, s.mem(), false)
}
var params *abi.ABIParamResultInfo
params = s.f.ABISelf.ABIAnalyze(fn.Type(), true)
// The backend's stackframe pass prunes away entries from the fn's
// Dcl list, including PARAMOUT nodes that correspond to output
// params passed in registers. Walk the Dcl list and capture these
// nodes to a side list, so that we'll have them available during
// DWARF-gen later on. See issue 48573 for more details.
var debugInfo ssa.FuncDebug
for _, n := range fn.Dcl {
if n.Class == ir.PPARAMOUT && n.IsOutputParamInRegisters() {
debugInfo.RegOutputParams = append(debugInfo.RegOutputParams, n)
}
}
fn.DebugInfo = &debugInfo
// Generate addresses of local declarations
s.decladdrs = map[*ir.Name]*ssa.Value{}
for _, n := range fn.Dcl {
switch n.Class {
case ir.PPARAM:
// Be aware that blank and unnamed input parameters will not appear here, but do appear in the type
s.decladdrs[n] = s.entryNewValue2A(ssa.OpLocalAddr, types.NewPtr(n.Type()), n, s.sp, s.startmem)
case ir.PPARAMOUT:
s.decladdrs[n] = s.entryNewValue2A(ssa.OpLocalAddr, types.NewPtr(n.Type()), n, s.sp, s.startmem)
case ir.PAUTO:
// processed at each use, to prevent Addr coming
// before the decl.
default:
s.Fatalf("local variable with class %v unimplemented", n.Class)
}
}
s.f.OwnAux = ssa.OwnAuxCall(fn.LSym, params)
// Populate SSAable arguments.
for _, n := range fn.Dcl {
if n.Class == ir.PPARAM {
if s.canSSA(n) {
v := s.newValue0A(ssa.OpArg, n.Type(), n)
s.vars[n] = v
s.addNamedValue(n, v) // This helps with debugging information, not needed for compilation itself.
} else { // address was taken AND/OR too large for SSA
paramAssignment := ssa.ParamAssignmentForArgName(s.f, n)
if len(paramAssignment.Registers) > 0 {
if TypeOK(n.Type()) { // SSA-able type, so address was taken -- receive value in OpArg, DO NOT bind to var, store immediately to memory.
v := s.newValue0A(ssa.OpArg, n.Type(), n)
s.store(n.Type(), s.decladdrs[n], v)
} else { // Too big for SSA.
// Brute force, and early, do a bunch of stores from registers
// TODO fix the nasty storeArgOrLoad recursion in ssa/expand_calls.go so this Just Works with store of a big Arg.
s.storeParameterRegsToStack(s.f.ABISelf, paramAssignment, n, s.decladdrs[n], false)
}
}
}
}
}
// Populate closure variables.
if fn.Needctxt() {
clo := s.entryNewValue0(ssa.OpGetClosurePtr, s.f.Config.Types.BytePtr)
offset := int64(types.PtrSize) // PtrSize to skip past function entry PC field
for _, n := range fn.ClosureVars {
typ := n.Type()
if !n.Byval() {
typ = types.NewPtr(typ)
}
offset = types.Rnd(offset, typ.Alignment())
ptr := s.newValue1I(ssa.OpOffPtr, types.NewPtr(typ), offset, clo)
offset += typ.Size()
// If n is a small variable captured by value, promote
// it to PAUTO so it can be converted to SSA.
//
// Note: While we never capture a variable by value if
// the user took its address, we may have generated
// runtime calls that did (#43701). Since we don't
// convert Addrtaken variables to SSA anyway, no point
// in promoting them either.
if n.Byval() && !n.Addrtaken() && TypeOK(n.Type()) {
n.Class = ir.PAUTO
fn.Dcl = append(fn.Dcl, n)
s.assign(n, s.load(n.Type(), ptr), false, 0)
continue
}
if !n.Byval() {
ptr = s.load(typ, ptr)
}
s.setHeapaddr(fn.Pos(), n, ptr)
}
}
// Convert the AST-based IR to the SSA-based IR
s.stmtList(fn.Enter)
s.zeroResults()
s.paramsToHeap()
s.stmtList(fn.Body)
// fallthrough to exit
if s.curBlock != nil {
s.pushLine(fn.Endlineno)
s.exit()
s.popLine()
}
for _, b := range s.f.Blocks {
if b.Pos != src.NoXPos {
s.updateUnsetPredPos(b)
}
}
s.f.HTMLWriter.WritePhase("before insert phis", "before insert phis")
s.insertPhis()
// Main call to ssa package to compile function
ssa.Compile(s.f)
if s.hasOpenDefers {
s.emitOpenDeferInfo()
}
// Record incoming parameter spill information for morestack calls emitted in the assembler.
// This is done here, using all the parameters (used, partially used, and unused) because
// it mimics the behavior of the former ABI (everything stored) and because it's not 100%
// clear if naming conventions are respected in autogenerated code.
// TODO figure out exactly what's unused, don't spill it. Make liveness fine-grained, also.
for _, p := range params.InParams() {
typs, offs := p.RegisterTypesAndOffsets()
for i, t := range typs {
o := offs[i] // offset within parameter
fo := p.FrameOffset(params) // offset of parameter in frame
reg := ssa.ObjRegForAbiReg(p.Registers[i], s.f.Config)
s.f.RegArgs = append(s.f.RegArgs, ssa.Spill{Reg: reg, Offset: fo + o, Type: t})
}
}
return s.f
}
func (s *state) storeParameterRegsToStack(abi *abi.ABIConfig, paramAssignment *abi.ABIParamAssignment, n *ir.Name, addr *ssa.Value, pointersOnly bool) {
typs, offs := paramAssignment.RegisterTypesAndOffsets()
for i, t := range typs {
if pointersOnly && !t.IsPtrShaped() {
continue
}
r := paramAssignment.Registers[i]
o := offs[i]
op, reg := ssa.ArgOpAndRegisterFor(r, abi)
aux := &ssa.AuxNameOffset{Name: n, Offset: o}
v := s.newValue0I(op, t, reg)
v.Aux = aux
p := s.newValue1I(ssa.OpOffPtr, types.NewPtr(t), o, addr)
s.store(t, p, v)
}
}
// zeroResults zeros the return values at the start of the function.
// We need to do this very early in the function. Defer might stop a
// panic and show the return values as they exist at the time of
// panic. For precise stacks, the garbage collector assumes results
// are always live, so we need to zero them before any allocations,
// even allocations to move params/results to the heap.
func (s *state) zeroResults() {
for _, f := range s.curfn.Type().Results().FieldSlice() {
n := f.Nname.(*ir.Name)
if !n.OnStack() {
// The local which points to the return value is the
// thing that needs zeroing. This is already handled
// by a Needzero annotation in plive.go:(*liveness).epilogue.
continue
}
// Zero the stack location containing f.
if typ := n.Type(); TypeOK(typ) {
s.assign(n, s.zeroVal(typ), false, 0)
} else {
s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, n, s.mem())
s.zero(n.Type(), s.decladdrs[n])
}
}
}
// paramsToHeap produces code to allocate memory for heap-escaped parameters
// and to copy non-result parameters' values from the stack.
func (s *state) paramsToHeap() {
do := func(params *types.Type) {
for _, f := range params.FieldSlice() {
if f.Nname == nil {
continue // anonymous or blank parameter
}
n := f.Nname.(*ir.Name)
if ir.IsBlank(n) || n.OnStack() {
continue
}
s.newHeapaddr(n)
if n.Class == ir.PPARAM {
s.move(n.Type(), s.expr(n.Heapaddr), s.decladdrs[n])
}
}
}
typ := s.curfn.Type()
do(typ.Recvs())
do(typ.Params())
do(typ.Results())
}
// newHeapaddr allocates heap memory for n and sets its heap address.
func (s *state) newHeapaddr(n *ir.Name) {
s.setHeapaddr(n.Pos(), n, s.newObject(n.Type()))
}
// setHeapaddr allocates a new PAUTO variable to store ptr (which must be non-nil)
// and then sets it as n's heap address.
func (s *state) setHeapaddr(pos src.XPos, n *ir.Name, ptr *ssa.Value) {
if !ptr.Type.IsPtr() || !types.Identical(n.Type(), ptr.Type.Elem()) {
base.FatalfAt(n.Pos(), "setHeapaddr %L with type %v", n, ptr.Type)
}
// Declare variable to hold address.
addr := ir.NewNameAt(pos, &types.Sym{Name: "&" + n.Sym().Name, Pkg: types.LocalPkg})
addr.SetType(types.NewPtr(n.Type()))
addr.Class = ir.PAUTO
addr.SetUsed(true)
addr.Curfn = s.curfn
s.curfn.Dcl = append(s.curfn.Dcl, addr)
types.CalcSize(addr.Type())
if n.Class == ir.PPARAMOUT {
addr.SetIsOutputParamHeapAddr(true)
}
n.Heapaddr = addr
s.assign(addr, ptr, false, 0)
}
// newObject returns an SSA value denoting new(typ).
func (s *state) newObject(typ *types.Type) *ssa.Value {
if typ.Size() == 0 {
return s.newValue1A(ssa.OpAddr, types.NewPtr(typ), ir.Syms.Zerobase, s.sb)
}
return s.rtcall(ir.Syms.Newobject, true, []*types.Type{types.NewPtr(typ)}, s.reflectType(typ))[0]
}
func (s *state) checkPtrAlignment(n *ir.ConvExpr, v *ssa.Value, count *ssa.Value) {
if !n.Type().IsPtr() {
s.Fatalf("expected pointer type: %v", n.Type())
}
elem := n.Type().Elem()
if count != nil {
if !elem.IsArray() {
s.Fatalf("expected array type: %v", elem)
}
elem = elem.Elem()
}
size := elem.Size()
// Casting from larger type to smaller one is ok, so for smallest type, do nothing.
if elem.Alignment() == 1 && (size == 0 || size == 1 || count == nil) {
return
}
if count == nil {
count = s.constInt(types.Types[types.TUINTPTR], 1)
}
if count.Type.Size() != s.config.PtrSize {
s.Fatalf("expected count fit to an uintptr size, have: %d, want: %d", count.Type.Size(), s.config.PtrSize)
}
s.rtcall(ir.Syms.CheckPtrAlignment, true, nil, v, s.reflectType(elem), count)
}
// reflectType returns an SSA value representing a pointer to typ's
// reflection type descriptor.
func (s *state) reflectType(typ *types.Type) *ssa.Value {
lsym := reflectdata.TypeLinksym(typ)
return s.entryNewValue1A(ssa.OpAddr, types.NewPtr(types.Types[types.TUINT8]), lsym, s.sb)
}
func dumpSourcesColumn(writer *ssa.HTMLWriter, fn *ir.Func) {
// Read sources of target function fn.
fname := base.Ctxt.PosTable.Pos(fn.Pos()).Filename()
targetFn, err := readFuncLines(fname, fn.Pos().Line(), fn.Endlineno.Line())
if err != nil {
writer.Logf("cannot read sources for function %v: %v", fn, err)
}
// Read sources of inlined functions.
var inlFns []*ssa.FuncLines
for _, fi := range ssaDumpInlined {
elno := fi.Endlineno
fname := base.Ctxt.PosTable.Pos(fi.Pos()).Filename()
fnLines, err := readFuncLines(fname, fi.Pos().Line(), elno.Line())
if err != nil {
writer.Logf("cannot read sources for inlined function %v: %v", fi, err)
continue
}
inlFns = append(inlFns, fnLines)
}
sort.Sort(ssa.ByTopo(inlFns))
if targetFn != nil {
inlFns = append([]*ssa.FuncLines{targetFn}, inlFns...)
}
writer.WriteSources("sources", inlFns)
}
func readFuncLines(file string, start, end uint) (*ssa.FuncLines, error) {
f, err := os.Open(os.ExpandEnv(file))
if err != nil {
return nil, err
}
defer f.Close()
var lines []string
ln := uint(1)
scanner := bufio.NewScanner(f)
for scanner.Scan() && ln <= end {
if ln >= start {
lines = append(lines, scanner.Text())
}
ln++
}
return &ssa.FuncLines{Filename: file, StartLineno: start, Lines: lines}, nil
}
// updateUnsetPredPos propagates the earliest-value position information for b
// towards all of b's predecessors that need a position, and recurs on that
// predecessor if its position is updated. B should have a non-empty position.
func (s *state) updateUnsetPredPos(b *ssa.Block) {
if b.Pos == src.NoXPos {
s.Fatalf("Block %s should have a position", b)
}
bestPos := src.NoXPos
for _, e := range b.Preds {
p := e.Block()
if !p.LackingPos() {
continue
}
if bestPos == src.NoXPos {
bestPos = b.Pos
for _, v := range b.Values {
if v.LackingPos() {
continue
}
if v.Pos != src.NoXPos {
// Assume values are still in roughly textual order;
// TODO: could also seek minimum position?
bestPos = v.Pos
break
}
}
}
p.Pos = bestPos
s.updateUnsetPredPos(p) // We do not expect long chains of these, thus recursion is okay.
}
}
// Information about each open-coded defer.
type openDeferInfo struct {
// The node representing the call of the defer
n *ir.CallExpr
// If defer call is closure call, the address of the argtmp where the
// closure is stored.
closure *ssa.Value
// The node representing the argtmp where the closure is stored - used for
// function, method, or interface call, to store a closure that panic
// processing can use for this defer.
closureNode *ir.Name
}
type state struct {
// configuration (arch) information
config *ssa.Config
// function we're building
f *ssa.Func
// Node for function
curfn *ir.Func
// labels in f
labels map[string]*ssaLabel
// unlabeled break and continue statement tracking
breakTo *ssa.Block // current target for plain break statement
continueTo *ssa.Block // current target for plain continue statement
// current location where we're interpreting the AST
curBlock *ssa.Block
// variable assignments in the current block (map from variable symbol to ssa value)
// *Node is the unique identifier (an ONAME Node) for the variable.
// TODO: keep a single varnum map, then make all of these maps slices instead?
vars map[ir.Node]*ssa.Value
// fwdVars are variables that are used before they are defined in the current block.
// This map exists just to coalesce multiple references into a single FwdRef op.
// *Node is the unique identifier (an ONAME Node) for the variable.
fwdVars map[ir.Node]*ssa.Value
// all defined variables at the end of each block. Indexed by block ID.
defvars []map[ir.Node]*ssa.Value
// addresses of PPARAM and PPARAMOUT variables on the stack.
decladdrs map[*ir.Name]*ssa.Value
// starting values. Memory, stack pointer, and globals pointer
startmem *ssa.Value
sp *ssa.Value
sb *ssa.Value
// value representing address of where deferBits autotmp is stored
deferBitsAddr *ssa.Value
deferBitsTemp *ir.Name
// line number stack. The current line number is top of stack
line []src.XPos
// the last line number processed; it may have been popped
lastPos src.XPos
// list of panic calls by function name and line number.
// Used to deduplicate panic calls.
panics map[funcLine]*ssa.Block
cgoUnsafeArgs bool
hasdefer bool // whether the function contains a defer statement
softFloat bool
hasOpenDefers bool // whether we are doing open-coded defers
checkPtrEnabled bool // whether to insert checkptr instrumentation
// If doing open-coded defers, list of info about the defer calls in
// scanning order. Hence, at exit we should run these defers in reverse
// order of this list
openDefers []*openDeferInfo
// For open-coded defers, this is the beginning and end blocks of the last
// defer exit code that we have generated so far. We use these to share
// code between exits if the shareDeferExits option (disabled by default)
// is on.
lastDeferExit *ssa.Block // Entry block of last defer exit code we generated
lastDeferFinalBlock *ssa.Block // Final block of last defer exit code we generated
lastDeferCount int // Number of defers encountered at that point
prevCall *ssa.Value // the previous call; use this to tie results to the call op.
}
type funcLine struct {
f *obj.LSym
base *src.PosBase
line uint
}
type ssaLabel struct {
target *ssa.Block // block identified by this label
breakTarget *ssa.Block // block to break to in control flow node identified by this label
continueTarget *ssa.Block // block to continue to in control flow node identified by this label
}
// label returns the label associated with sym, creating it if necessary.
func (s *state) label(sym *types.Sym) *ssaLabel {
lab := s.labels[sym.Name]
if lab == nil {
lab = new(ssaLabel)
s.labels[sym.Name] = lab
}
return lab
}
func (s *state) Logf(msg string, args ...interface{}) { s.f.Logf(msg, args...) }
func (s *state) Log() bool { return s.f.Log() }
func (s *state) Fatalf(msg string, args ...interface{}) {
s.f.Frontend().Fatalf(s.peekPos(), msg, args...)
}
func (s *state) Warnl(pos src.XPos, msg string, args ...interface{}) { s.f.Warnl(pos, msg, args...) }
func (s *state) Debug_checknil() bool { return s.f.Frontend().Debug_checknil() }
func ssaMarker(name string) *ir.Name {
return typecheck.NewName(&types.Sym{Name: name})
}
var (
// marker node for the memory variable
memVar = ssaMarker("mem")
// marker nodes for temporary variables
ptrVar = ssaMarker("ptr")
lenVar = ssaMarker("len")
newlenVar = ssaMarker("newlen")
capVar = ssaMarker("cap")
typVar = ssaMarker("typ")
okVar = ssaMarker("ok")
deferBitsVar = ssaMarker("deferBits")
)
// startBlock sets the current block we're generating code in to b.
func (s *state) startBlock(b *ssa.Block) {
if s.curBlock != nil {
s.Fatalf("starting block %v when block %v has not ended", b, s.curBlock)
}
s.curBlock = b
s.vars = map[ir.Node]*ssa.Value{}
for n := range s.fwdVars {
delete(s.fwdVars, n)
}
}
// endBlock marks the end of generating code for the current block.
// Returns the (former) current block. Returns nil if there is no current
// block, i.e. if no code flows to the current execution point.
func (s *state) endBlock() *ssa.Block {
b := s.curBlock
if b == nil {
return nil
}
for len(s.defvars) <= int(b.ID) {
s.defvars = append(s.defvars, nil)
}
s.defvars[b.ID] = s.vars
s.curBlock = nil
s.vars = nil
if b.LackingPos() {
// Empty plain blocks get the line of their successor (handled after all blocks created),
// except for increment blocks in For statements (handled in ssa conversion of OFOR),
// and for blocks ending in GOTO/BREAK/CONTINUE.
b.Pos = src.NoXPos
} else {
b.Pos = s.lastPos
}
return b
}
// pushLine pushes a line number on the line number stack.
func (s *state) pushLine(line src.XPos) {
if !line.IsKnown() {
// the frontend may emit node with line number missing,
// use the parent line number in this case.
line = s.peekPos()
if base.Flag.K != 0 {
base.Warn("buildssa: unknown position (line 0)")
}
} else {
s.lastPos = line
}
s.line = append(s.line, line)
}