// 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"
"encoding/binary"
"fmt"
"io"
"math"
"math/bits"
"os"
"path/filepath"
)
func applyRewrite(f *Func, rb blockRewriter, rv valueRewriter) {
// repeat rewrites until we find no more rewrites
pendingLines := f.cachedLineStarts // Holds statement boundaries that need to be moved to a new value/block
pendingLines.clear()
for {
change := false
for _, b := range f.Blocks {
if b.Control != nil && b.Control.Op == OpCopy {
for b.Control.Op == OpCopy {
b.SetControl(b.Control.Args[0])
}
}
if rb(b) {
change = true
}
for j, v := range b.Values {
change = phielimValue(v) || change
// Eliminate copy inputs.
// If any copy input becomes unused, mark it
// as invalid and discard its argument. Repeat
// recursively on the discarded argument.
// This phase helps remove phantom "dead copy" uses
// of a value so that a x.Uses==1 rule condition
// fires reliably.
for i, a := range v.Args {
if a.Op != OpCopy {
continue
}
aa := copySource(a)
v.SetArg(i, aa)
// If a, a copy, has a line boundary indicator, attempt to find a new value
// to hold it. The first candidate is the value that will replace a (aa),
// if it shares the same block and line and is eligible.
// The second option is v, which has a as an input. Because aa is earlier in
// the data flow, it is the better choice.
if a.Pos.IsStmt() == src.PosIsStmt {
if aa.Block == a.Block && aa.Pos.Line() == a.Pos.Line() && aa.Pos.IsStmt() != src.PosNotStmt {
aa.Pos = aa.Pos.WithIsStmt()
} else if v.Block == a.Block && v.Pos.Line() == a.Pos.Line() && v.Pos.IsStmt() != src.PosNotStmt {
v.Pos = v.Pos.WithIsStmt()
} else {
// Record the lost line and look for a new home after all rewrites are complete.
// TODO: it's possible (in FOR loops, in particular) for statement boundaries for the same
// line to appear in more than one block, but only one block is stored, so if both end
// up here, then one will be lost.
pendingLines.set(a.Pos, int32(a.Block.ID))
}
a.Pos = a.Pos.WithNotStmt()
}
change = true
for a.Uses == 0 {
b := a.Args[0]
a.reset(OpInvalid)
a = b
}
}
// apply rewrite function
if rv(v) {
change = true
// If value changed to a poor choice for a statement boundary, move the boundary
if v.Pos.IsStmt() == src.PosIsStmt {
if k := nextGoodStatementIndex(v, j, b); k != j {
v.Pos = v.Pos.WithNotStmt()
b.Values[k].Pos = b.Values[k].Pos.WithIsStmt()
}
}
}
}
}
if !change {
break
}
}
// remove clobbered values
for _, b := range f.Blocks {
j := 0
for i, v := range b.Values {
vl := v.Pos
if v.Op == OpInvalid {
if v.Pos.IsStmt() == src.PosIsStmt {
pendingLines.set(vl, int32(b.ID))
}
f.freeValue(v)
continue
}
if v.Pos.IsStmt() != src.PosNotStmt && pendingLines.get(vl) == int32(b.ID) {
pendingLines.remove(vl)
v.Pos = v.Pos.WithIsStmt()
}
if i != j {
b.Values[j] = v
}
j++
}
if pendingLines.get(b.Pos) == int32(b.ID) {
b.Pos = b.Pos.WithIsStmt()
pendingLines.remove(b.Pos)
}
if j != len(b.Values) {
tail := b.Values[j:]
for j := range tail {
tail[j] = nil
}
b.Values = b.Values[:j]
}
}
}
// Common functions called from rewriting rules
func is64BitFloat(t *types.Type) bool {
return t.Size() == 8 && t.IsFloat()
}
func is32BitFloat(t *types.Type) bool {
return t.Size() == 4 && t.IsFloat()
}
func is64BitInt(t *types.Type) bool {
return t.Size() == 8 && t.IsInteger()
}
func is32BitInt(t *types.Type) bool {
return t.Size() == 4 && t.IsInteger()
}
func is16BitInt(t *types.Type) bool {
return t.Size() == 2 && t.IsInteger()
}
func is8BitInt(t *types.Type) bool {
return t.Size() == 1 && t.IsInteger()
}
func isPtr(t *types.Type) bool {
return t.IsPtrShaped()
}
func isSigned(t *types.Type) bool {
return t.IsSigned()
}
// mergeSym merges two symbolic offsets. There is no real merging of
// offsets, we just pick the non-nil one.
func mergeSym(x, y interface{}) interface{} {
if x == nil {
return y
}
if y == nil {
return x
}
panic(fmt.Sprintf("mergeSym with two non-nil syms %s %s", x, y))
}
func canMergeSym(x, y interface{}) bool {
return x == nil || y == nil
}
// canMergeLoadClobber reports whether the load can be merged into target without
// invalidating the schedule.
// It also checks that the other non-load argument x is something we
// are ok with clobbering.
func canMergeLoadClobber(target, load, x *Value) bool {
// The register containing x is going to get clobbered.
// Don't merge if we still need the value of x.
// We don't have liveness information here, but we can
// approximate x dying with:
// 1) target is x's only use.
// 2) target is not in a deeper loop than x.
if x.Uses != 1 {
return false
}
loopnest := x.Block.Func.loopnest()
loopnest.calculateDepths()
if loopnest.depth(target.Block.ID) > loopnest.depth(x.Block.ID) {
return false
}
return canMergeLoad(target, load)
}
// canMergeLoad reports whether the load can be merged into target without
// invalidating the schedule.
func canMergeLoad(target, load *Value) bool {
if target.Block.ID != load.Block.ID {
// If the load is in a different block do not merge it.
return false
}
// We can't merge the load into the target if the load
// has more than one use.
if load.Uses != 1 {
return false
}
mem := load.MemoryArg()
// We need the load's memory arg to still be alive at target. That
// can't be the case if one of target's args depends on a memory
// state that is a successor of load's memory arg.
//
// For example, it would be invalid to merge load into target in
// the following situation because newmem has killed oldmem
// before target is reached:
// load = read ... oldmem
// newmem = write ... oldmem
// arg0 = read ... newmem
// target = add arg0 load
//
// If the argument comes from a different block then we can exclude
// it immediately because it must dominate load (which is in the
// same block as target).
var args []*Value
for _, a := range target.Args {
if a != load && a.Block.ID == target.Block.ID {
args = append(args, a)
}
}
// memPreds contains memory states known to be predecessors of load's
// memory state. It is lazily initialized.
var memPreds map[*Value]bool
for i := 0; len(args) > 0; i++ {
const limit = 100
if i >= limit {
// Give up if we have done a lot of iterations.
return false
}
v := args[len(args)-1]
args = args[:len(args)-1]
if target.Block.ID != v.Block.ID {
// Since target and load are in the same block
// we can stop searching when we leave the block.
continue
}
if v.Op == OpPhi {
// A Phi implies we have reached the top of the block.
// The memory phi, if it exists, is always
// the first logical store in the block.
continue
}
if v.Type.IsTuple() && v.Type.FieldType(1).IsMemory() {
// We could handle this situation however it is likely
// to be very rare.
return false
}
if v.Op.SymEffect()&SymAddr != 0 {
// This case prevents an operation that calculates the
// address of a local variable from being forced to schedule
// before its corresponding VarDef.
// See issue 28445.
// v1 = LOAD ...
// v2 = VARDEF
// v3 = LEAQ
// v4 = CMPQ v1 v3
// We don't want to combine the CMPQ with the load, because
// that would force the CMPQ to schedule before the VARDEF, which
// in turn requires the LEAQ to schedule before the VARDEF.
return false
}
if v.Type.IsMemory() {
if memPreds == nil {
// Initialise a map containing memory states
// known to be predecessors of load's memory
// state.
memPreds = make(map[*Value]bool)
m := mem
const limit = 50
for i := 0; i < limit; i++ {
if m.Op == OpPhi {
// The memory phi, if it exists, is always
// the first logical store in the block.
break
}
if m.Block.ID != target.Block.ID {
break
}
if !m.Type.IsMemory() {
break
}
memPreds[m] = true
if len(m.Args) == 0 {
break
}
m = m.MemoryArg()
}
}
// We can merge if v is a predecessor of mem.
//
// For example, we can merge load into target in the
// following scenario:
// x = read ... v
// mem = write ... v
// load = read ... mem
// target = add x load
if memPreds[v] {
continue
}
return false
}
if len(v.Args) > 0 && v.Args[len(v.Args)-1] == mem {
// If v takes mem as an input then we know mem
// is valid at this point.
continue
}
for _, a := range v.Args {
if target.Block.ID == a.Block.ID {
args = append(args, a)
}
}
}
return true
}
// isSameSym reports whether sym is the same as the given named symbol
func isSameSym(sym interface{}, name string) bool {
s, ok := sym.(fmt.Stringer)
return ok && s.String() == name
}
// nlz returns the number of leading zeros.
func nlz(x int64) int64 {
return int64(bits.LeadingZeros64(uint64(x)))
}
// ntz returns the number of trailing zeros.
func ntz(x int64) int64 {
return int64(bits.TrailingZeros64(uint64(x)))
}
func oneBit(x int64) bool {
return bits.OnesCount64(uint64(x)) == 1
}
// nlo returns the number of leading ones.
func nlo(x int64) int64 {
return nlz(^x)
}
// nto returns the number of trailing ones.
func nto(x int64) int64 {
return ntz(^x)
}
// log2 returns logarithm in base 2 of uint64(n), with log2(0) = -1.
// Rounds down.
func log2(n int64) int64 {
return int64(bits.Len64(uint64(n))) - 1
}
// log2uint32 returns logarithm in base 2 of uint32(n), with log2(0) = -1.
// Rounds down.
func log2uint32(n int64) int64 {
return int64(bits.Len32(uint32(n))) - 1
}
// isPowerOfTwo reports whether n is a power of 2.
func isPowerOfTwo(n int64) bool {
return n > 0 && n&(n-1) == 0
}
// isUint64PowerOfTwo reports whether uint64(n) is a power of 2.
func isUint64PowerOfTwo(in int64) bool {
n := uint64(in)
return n > 0 && n&(n-1) == 0
}
// isUint32PowerOfTwo reports whether uint32(n) is a power of 2.
func isUint32PowerOfTwo(in int64) bool {
n := uint64(uint32(in))
return n > 0 && n&(n-1) == 0
}
// is32Bit reports whether n can be represented as a signed 32 bit integer.
func is32Bit(n int64) bool {
return n == int64(int32(n))
}
// is16Bit reports whether n can be represented as a signed 16 bit integer.
func is16Bit(n int64) bool {
return n == int64(int16(n))
}
// isU12Bit reports whether n can be represented as an unsigned 12 bit integer.
func isU12Bit(n int64) bool {
return 0 <= n && n < (1<<12)
}
// isU16Bit reports whether n can be represented as an unsigned 16 bit integer.
func isU16Bit(n int64) bool {
return n == int64(uint16(n))
}
// isU32Bit reports whether n can be represented as an unsigned 32 bit integer.
func isU32Bit(n int64) bool {
return n == int64(uint32(n))
}
// is20Bit reports whether n can be represented as a signed 20 bit integer.
func is20Bit(n int64) bool {
return -(1<<19) <= n && n < (1<<19)
}
// b2i translates a boolean value to 0 or 1 for assigning to auxInt.
func b2i(b bool) int64 {
if b {
return 1
}
return 0
}
// shiftIsBounded reports whether (left/right) shift Value v is known to be bounded.
// A shift is bounded if it is shifting by less than the width of the shifted value.
func shiftIsBounded(v *Value) bool {
return v.AuxInt != 0
}
// truncate64Fto32F converts a float64 value to a float32 preserving the bit pattern
// of the mantissa. It will panic if the truncation results in lost information.
func truncate64Fto32F(f float64) float32 {
if !isExactFloat32(f) {
panic("truncate64Fto32F: truncation is not exact")
}
if !math.IsNaN(f) {
return float32(f)
}
// NaN bit patterns aren't necessarily preserved across conversion
// instructions so we need to do the conversion manually.
b := math.Float64bits(f)
m := b & ((1 << 52) - 1) // mantissa (a.k.a. significand)
// | sign | exponent | mantissa |
r := uint32(((b >> 32) & (1 << 31)) | 0x7f800000 | (m >> (52 - 23)))
return math.Float32frombits(r)
}
// extend32Fto64F converts a float32 value to a float64 value preserving the bit
// pattern of the mantissa.
func extend32Fto64F(f float32) float64 {
if !math.IsNaN(float64(f)) {
return float64(f)
}
// NaN bit patterns aren't necessarily preserved across conversion
// instructions so we need to do the conversion manually.
b := uint64(math.Float32bits(f))
// | sign | exponent | mantissa |
r := ((b << 32) & (1 << 63)) | (0x7ff << 52) | ((b & 0x7fffff) << (52 - 23))
return math.Float64frombits(r)
}
// NeedsFixUp reports whether the division needs fix-up code.
func NeedsFixUp(v *Value) bool {
return v.AuxInt == 0
}
// i2f is used in rules for converting from an AuxInt to a float.
func i2f(i int64) float64 {
return math.Float64frombits(uint64(i))
}
// auxFrom64F encodes a float64 value so it can be stored in an AuxInt.
func auxFrom64F(f float64) int64 {
return int64(math.Float64bits(f))
}
// auxFrom32F encodes a float32 value so it can be stored in an AuxInt.
func auxFrom32F(f float32) int64 {
return int64(math.Float64bits(extend32Fto64F(f)))
}
// auxTo32F decodes a float32 from the AuxInt value provided.
func auxTo32F(i int64) float32 {
return truncate64Fto32F(math.Float64frombits(uint64(i)))
}
// auxTo64F decodes a float64 from the AuxInt value provided.
func auxTo64F(i int64) float64 {
return math.Float64frombits(uint64(i))
}
// uaddOvf reports whether unsigned a+b would overflow.
func uaddOvf(a, b int64) bool {
return uint64(a)+uint64(b) < uint64(a)
}
// de-virtualize an InterCall
// 'sym' is the symbol for the itab
func devirt(v *Value, sym interface{}, offset int64) *obj.LSym {
f := v.Block.Func
n, ok := sym.(*obj.LSym)
if !ok {
return nil
}
lsym := f.fe.DerefItab(n, offset)
if f.pass.debug > 0 {
if lsym != nil {
f.Warnl(v.Pos, "de-virtualizing call")
} else {
f.Warnl(v.Pos, "couldn't de-virtualize call")
}
}
return lsym
}
// isSamePtr reports whether p1 and p2 point to the same address.
func isSamePtr(p1, p2 *Value) bool {
if p1 == p2 {
return true
}
if p1.Op != p2.Op {
return false
}
switch p1.Op {
case OpOffPtr:
return p1.AuxInt == p2.AuxInt && isSamePtr(p1.Args[0], p2.Args[0])
case OpAddr, OpLocalAddr:
// OpAddr's 0th arg is either OpSP or OpSB, which means that it is uniquely identified by its Op.
// Checking for value equality only works after [z]cse has run.
return p1.Aux == p2.Aux && p1.Args[0].Op == p2.Args[0].Op
case OpAddPtr:
return p1.Args[1] == p2.Args[1] && isSamePtr(p1.Args[0], p2.Args[0])
}
return false
}
func isStackPtr(v *Value) bool {
for v.Op == OpOffPtr || v.Op == OpAddPtr {
v = v.Args[0]
}
return v.Op == OpSP || v.Op == OpLocalAddr
}
// disjoint reports whether the memory region specified by [p1:p1+n1)
// does not overlap with [p2:p2+n2).
// A return value of false does not imply the regions overlap.
func disjoint(p1 *Value, n1 int64, p2 *Value, n2 int64) bool {
if n1 == 0 || n2 == 0 {
return true
}
if p1 == p2 {
return false
}
baseAndOffset := func(ptr *Value) (base *Value, offset int64) {
base, offset = ptr, 0
for base.Op == OpOffPtr {
offset += base.AuxInt
base = base.Args[0]
}
return base, offset
}
p1, off1 := baseAndOffset(p1)
p2, off2 := baseAndOffset(p2)
if isSamePtr(p1, p2) {
return !overlap(off1, n1, off2, n2)
}
// p1 and p2 are not the same, so if they are both OpAddrs then
// they point to different variables.
// If one pointer is on the stack and the other is an argument
// then they can't overlap.
switch p1.Op {
case OpAddr, OpLocalAddr:
if p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpSP {
return true
}
return p2.Op == OpArg && p1.Args[0].Op == OpSP
case OpArg:
if p2.Op == OpSP || p2.Op == OpLocalAddr {
return true
}
case OpSP:
return p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpArg || p2.Op == OpSP
}
return false
}
// moveSize returns the number of bytes an aligned MOV instruction moves
func moveSize(align int64, c *Config) int64 {
switch {
case align%8 == 0 && c.PtrSize == 8:
return 8
case align%4 == 0:
return 4
case align%2 == 0:
return 2
}
return 1
}
// mergePoint finds a block among a's blocks which dominates b and is itself
// dominated by all of a's blocks. Returns nil if it can't find one.
// Might return nil even if one does exist.
func mergePoint(b *Block, a ...*Value) *Block {
// Walk backward from b looking for one of the a's blocks.
// Max distance
d := 100
for d > 0 {
for _, x := range a {
if b == x.Block {
goto found
}
}
if len(b.Preds) > 1 {
// Don't know which way to go back. Abort.
return nil
}
b = b.Preds[0].b
d--
}
return nil // too far away
found:
// At this point, r is the first value in a that we find by walking backwards.
// if we return anything, r will be it.
r := b
// Keep going, counting the other a's that we find. They must all dominate r.
na := 0
for d > 0 {
for _, x := range a {
if b == x.Block {
na++
}
}
if na == len(a) {
// Found all of a in a backwards walk. We can return r.
return r
}
if len(b.Preds) > 1 {
return nil
}
b = b.Preds[0].b
d--
}
return nil // too far away
}
// clobber invalidates v. Returns true.
// clobber is used by rewrite rules to:
// A) make sure v is really dead and never used again.
// B) decrement use counts of v's args.
func clobber(v *Value) bool {
v.reset(OpInvalid)
// Note: leave v.Block intact. The Block field is used after clobber.
return true
}
// clobberIfDead resets v when use count is 1. Returns true.
// clobberIfDead is used by rewrite rules to decrement
// use counts of v's args when v is dead and never used.
func clobberIfDead(v *Value) bool {
if v.Uses == 1 {
v.reset(OpInvalid)
}
// Note: leave v.Block intact. The Block field is used after clobberIfDead.
return true
}
// noteRule is an easy way to track if a rule is matched when writing
// new ones. Make the rule of interest also conditional on
// noteRule("note to self: rule of interest matched")
// and that message will print when the rule matches.
func noteRule(s string) bool {
fmt.Println(s)
return true
}
// countRule increments Func.ruleMatches[key].
// If Func.ruleMatches is non-nil at the end
// of compilation, it will be printed to stdout.
// This is intended to make it easier to find which functions
// which contain lots of rules matches when developing new rules.
func countRule(v *Value, key string) bool {
f := v.Block.Func
if f.ruleMatches == nil {
f.ruleMatches = make(map[string]int)
}
f.ruleMatches[key]++
return true
}
// warnRule generates compiler debug output with string s when
// v is not in autogenerated code, cond is true and the rule has fired.
func warnRule(cond bool, v *Value, s string) bool {
if pos := v.Pos; pos.Line() > 1 && cond {
v.Block.Func.Warnl(pos, s)
}
return true
}
// for a pseudo-op like (LessThan x), extract x
func flagArg(v *Value) *Value {
if len(v.Args) != 1 || !v.Args[0].Type.IsFlags() {
return nil
}
return v.Args[0]
}
// arm64Negate finds the complement to an ARM64 condition code,
// for example Equal -> NotEqual or LessThan -> GreaterEqual
//
// TODO: add floating-point conditions
func arm64Negate(op Op) Op {
switch op {
case OpARM64LessThan:
return OpARM64GreaterEqual
case OpARM64LessThanU:
return OpARM64GreaterEqualU
case OpARM64GreaterThan:
return OpARM64LessEqual
case OpARM64GreaterThanU:
return OpARM64LessEqualU
case OpARM64LessEqual:
return OpARM64GreaterThan
case OpARM64LessEqualU:
return OpARM64GreaterThanU
case OpARM64GreaterEqual:
return OpARM64LessThan
case OpARM64GreaterEqualU:
return OpARM64LessThanU
case OpARM64Equal:
return OpARM64NotEqual
case OpARM64NotEqual:
return OpARM64Equal
case OpARM64LessThanF:
return OpARM64GreaterEqualF
case OpARM64GreaterThanF:
return OpARM64LessEqualF
case OpARM64LessEqualF:
return OpARM64GreaterThanF
case OpARM64GreaterEqualF:
return OpARM64LessThanF
default:
panic("unreachable")
}
}
// arm64Invert evaluates (InvertFlags op), which
// is the same as altering the condition codes such
// that the same result would be produced if the arguments
// to the flag-generating instruction were reversed, e.g.
// (InvertFlags (CMP x y)) -> (CMP y x)
//
// TODO: add floating-point conditions
func arm64Invert(op Op) Op {
switch op {
case OpARM64LessThan:
return OpARM64GreaterThan
case OpARM64LessThanU:
return OpARM64GreaterThanU
case OpARM64GreaterThan:
return OpARM64LessThan
case OpARM64GreaterThanU:
return OpARM64LessThanU
case OpARM64LessEqual:
return OpARM64GreaterEqual
case OpARM64LessEqualU:
return OpARM64GreaterEqualU
case OpARM64GreaterEqual:
return OpARM64LessEqual
case OpARM64GreaterEqualU:
return OpARM64LessEqualU
case OpARM64Equal, OpARM64NotEqual:
return op
case OpARM64LessThanF:
return OpARM64GreaterThanF
case OpARM64GreaterThanF:
return OpARM64LessThanF
case OpARM64LessEqualF:
return OpARM64GreaterEqualF
case OpARM64GreaterEqualF:
return OpARM64LessEqualF
default:
panic("unreachable")
}
}
// evaluate an ARM64 op against a flags value
// that is potentially constant; return 1 for true,
// -1 for false, and 0 for not constant.
func ccARM64Eval(cc interface{}, flags *Value) int {
op := cc.(Op)
fop := flags.Op
switch fop {
case OpARM64InvertFlags:
return -ccARM64Eval(op, flags.Args[0])
case OpARM64FlagEQ:
switch op {
case OpARM64Equal, OpARM64GreaterEqual, OpARM64LessEqual,
OpARM64GreaterEqualU, OpARM64LessEqualU:
return 1
default:
return -1
}
case OpARM64FlagLT_ULT:
switch op {
case OpARM64LessThan, OpARM64LessThanU,
OpARM64LessEqual, OpARM64LessEqualU:
return 1
default:
return -1
}
case OpARM64FlagLT_UGT:
switch op {
case OpARM64LessThan, OpARM64GreaterThanU,
OpARM64LessEqual, OpARM64GreaterEqualU:
return 1
default:
return -1
}
case OpARM64FlagGT_ULT:
switch op {
case OpARM64GreaterThan, OpARM64LessThanU,
OpARM64GreaterEqual, OpARM64LessEqualU:
return 1
default:
return -1
}
case OpARM64FlagGT_UGT:
switch op {
case OpARM64GreaterThan, OpARM64GreaterThanU,
OpARM64GreaterEqual, OpARM64GreaterEqualU:
return 1
default:
return -1
}
default:
return 0
}
}
// logRule logs the use of the rule s. This will only be enabled if
// rewrite rules were generated with the -log option, see gen/rulegen.go.
func logRule(s string) {
if ruleFile == nil {
// Open a log file to write log to. We open in append
// mode because all.bash runs the compiler lots of times,
// and we want the concatenation of all of those logs.
// This means, of course, that users need to rm the old log
// to get fresh data.
// TODO: all.bash runs compilers in parallel. Need to synchronize logging somehow?
w, err := os.OpenFile(filepath.Join(os.Getenv("GOROOT"), "src", "rulelog"),
os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
if err != nil {
panic(err)
}
ruleFile = w
}
_, err := fmt.Fprintln(ruleFile, s)
if err != nil {
panic(err)
}
}
var ruleFile io.Writer
func min(x, y int64) int64 {
if x < y {
return x
}
return y
}
func isConstZero(v *Value) bool {
switch v.Op {
case OpConstNil:
return true
case OpConst64, OpConst32, OpConst16, OpConst8, OpConstBool, OpConst32F, OpConst64F:
return v.AuxInt == 0
}
return false
}
// reciprocalExact64 reports whether 1/c is exactly representable.
func reciprocalExact64(c float64) bool {
b := math.Float64bits(c)
man := b & (1<<52 - 1)
if man != 0 {
return false // not a power of 2, denormal, or NaN
}
exp := b >> 52 & (1<<11 - 1)
// exponent bias is 0x3ff. So taking the reciprocal of a number
// changes the exponent to 0x7fe-exp.
switch exp {
case 0:
return false // ±0
case 0x7ff:
return false // ±inf
case 0x7fe:
return false // exponent is not representable
default:
return true
}
}
// reciprocalExact32 reports whether 1/c is exactly representable.
func reciprocalExact32(c float32) bool {
b := math.Float32bits(c)
man := b & (1<<23 - 1)
if man != 0 {
return false // not a power of 2, denormal, or NaN
}
exp := b >> 23 & (1<<8 - 1)
// exponent bias is 0x7f. So taking the reciprocal of a number
// changes the exponent to 0xfe-exp.
switch exp {
case 0:
return false // ±0
case 0xff:
return false // ±inf
case 0xfe:
return false // exponent is not representable
default:
return true
}
}
// check if an immediate can be directly encoded into an ARM's instruction
func isARMImmRot(v uint32) bool {
for i := 0; i < 16; i++ {
if v&^0xff == 0 {
return true
}
v = v<<2 | v>>30
}
return false
}
// overlap reports whether the ranges given by the given offset and
// size pairs overlap.
func overlap(offset1, size1, offset2, size2 int64) bool {
if offset1 >= offset2 && offset2+size2 > offset1 {
return true
}
if offset2 >= offset1 && offset1+size1 > offset2 {
return true
}
return false
}
func areAdjacentOffsets(off1, off2, size int64) bool {
return off1+size == off2 || off1 == off2+size
}
// check if value zeroes out upper 32-bit of 64-bit register.
// depth limits recursion depth. In AMD64.rules 3 is used as limit,
// because it catches same amount of cases as 4.
func zeroUpper32Bits(x *Value, depth int) bool {
switch x.Op {
case OpAMD64MOVLconst, OpAMD64MOVLload, OpAMD64MOVLQZX, OpAMD64MOVLloadidx1,
OpAMD64MOVWload, OpAMD64MOVWloadidx1, OpAMD64MOVBload, OpAMD64MOVBloadidx1,
OpAMD64MOVLloadidx4, OpAMD64ADDLload, OpAMD64SUBLload, OpAMD64ANDLload,
OpAMD64ORLload, OpAMD64XORLload, OpAMD64CVTTSD2SL,
OpAMD64ADDL, OpAMD64ADDLconst, OpAMD64SUBL, OpAMD64SUBLconst,
OpAMD64ANDL, OpAMD64ANDLconst, OpAMD64ORL, OpAMD64ORLconst,
OpAMD64XORL, OpAMD64XORLconst, OpAMD64NEGL, OpAMD64NOTL:
return true
case OpArg:
return x.Type.Width == 4
case OpPhi, OpSelect0, OpSelect1:
// Phis can use each-other as an arguments, instead of tracking visited values,
// just limit recursion depth.
if depth <= 0 {
return false
}
for i := range x.Args {
if !zeroUpper32Bits(x.Args[i], depth-1) {
return false
}
}
return true
}
return false
}
// zeroUpper48Bits is similar to zeroUpper32Bits, but for upper 48 bits
func zeroUpper48Bits(x *Value, depth int) bool {
switch x.Op {
case OpAMD64MOVWQZX, OpAMD64MOVWload, OpAMD64MOVWloadidx1, OpAMD64MOVWloadidx2:
return true
case OpArg:
return x.Type.Width == 2
case OpPhi, OpSelect0, OpSelect1:
// Phis can use each-other as an arguments, instead of tracking visited values,
// just limit recursion depth.
if depth <= 0 {
return false
}
for i := range x.Args {
if !zeroUpper48Bits(x.Args[i], depth-1) {
return false
}
}
return true
}
return false
}
// zeroUpper56Bits is similar to zeroUpper32Bits, but for upper 56 bits
func zeroUpper56Bits(x *Value, depth int) bool {
switch x.Op {
case OpAMD64MOVBQZX, OpAMD64MOVBload, OpAMD64MOVBloadidx1:
return true
case OpArg:
return x.Type.Width == 1
case OpPhi, OpSelect0, OpSelect1:
// Phis can use each-other as an arguments, instead of tracking visited values,
// just limit recursion depth.
if depth <= 0 {
return false
}
for i := range x.Args {
if !zeroUpper56Bits(x.Args[i], depth-1) {
return false
}
}
return true
}
return false
}
// isInlinableMemmove reports whether the given arch performs a Move of the given size
// faster than memmove. It will only return true if replacing the memmove with a Move is
// safe, either because Move is small or because the arguments are disjoint.
// This is used as a check for replacing memmove with Move ops.
func isInlinableMemmove(dst, src *Value, sz int64, c *Config) bool {
// It is always safe to convert memmove into Move when its arguments are disjoint.
// Move ops may or may not be faster for large sizes depending on how the platform
// lowers them, so we only perform this optimization on platforms that we know to
// have fast Move ops.
switch c.arch {
case "amd64", "amd64p32":
return sz <= 16 || (sz < 1024 && disjoint(dst, sz, src, sz))
case "386", "ppc64", "ppc64le", "arm64":
return sz <= 8
case "s390x":
return sz <= 8 || disjoint(dst, sz, src, sz)
case "arm", "mips", "mips64", "mipsle", "mips64le":
return sz <= 4
}
return false
}
// hasSmallRotate reports whether the architecture has rotate instructions
// for sizes < 32-bit. This is used to decide whether to promote some rotations.
func hasSmallRotate(c *Config) bool {
switch c.arch {
case "amd64", "amd64p32", "386":
return true
default:
return false
}
}
// encodes the lsb and width for arm(64) bitfield ops into the expected auxInt format.
func armBFAuxInt(lsb, width int64) int64 {
if lsb < 0 || lsb > 63 {
panic("ARM(64) bit field lsb constant out of range")
}
if width < 1 || width > 64 {
panic("ARM(64) bit field width constant out of range")
}
return width | lsb<<8
}
// returns the lsb part of the auxInt field of arm64 bitfield ops.
func getARM64BFlsb(bfc int64) int64 {
return int64(uint64(bfc) >> 8)
}
// returns the width part of the auxInt field of arm64 bitfield ops.
func getARM64BFwidth(bfc int64) int64 {
return bfc & 0xff
}
// checks if mask >> rshift applied at lsb is a valid arm64 bitfield op mask.
func isARM64BFMask(lsb, mask, rshift int64) bool {
shiftedMask := int64(uint64(mask) >> uint64(rshift))
return shiftedMask != 0 && isPowerOfTwo(shiftedMask+1) && nto(shiftedMask)+lsb < 64
}
// returns the bitfield width of mask >> rshift for arm64 bitfield ops
func arm64BFWidth(mask, rshift int64) int64 {
shiftedMask := int64(uint64(mask) >> uint64(rshift))
if shiftedMask == 0 {
panic("ARM64 BF mask is zero")
}
return nto(shiftedMask)
}
// sizeof returns the size of t in bytes.
// It will panic if t is not a *types.Type.
func sizeof(t interface{}) int64 {
return t.(*types.Type).Size()
}
// alignof returns the alignment of t in bytes.
// It will panic if t is not a *types.Type.
func alignof(t interface{}) int64 {
return t.(*types.Type).Alignment()
}
// registerizable reports whether t is a primitive type that fits in
// a register. It assumes float64 values will always fit into registers
// even if that isn't strictly true.
// It will panic if t is not a *types.Type.
func registerizable(b *Block, t interface{}) bool {
typ := t.(*types.Type)
if typ.IsPtrShaped() || typ.IsFloat() {
return true
}
if typ.IsInteger() {
return typ.Size() <= b.Func.Config.RegSize
}
return false
}
// needRaceCleanup reports whether this call to racefuncenter/exit isn't needed.
func needRaceCleanup(sym interface{}, v *Value) bool {
f := v.Block.Func
if !f.Config.Race {
return false
}
if !isSameSym(sym, "runtime.racefuncenter") && !isSameSym(sym, "runtime.racefuncexit") {
return false
}
for _, b := range f.Blocks {
for _, v := range b.Values {
switch v.Op {
case OpStaticCall:
// Check for racefuncenter will encounter racefuncexit and vice versa.
// Allow calls to panic*
s := v.Aux.(fmt.Stringer).String()
switch s {
case "runtime.racefuncenter", "runtime.racefuncexit",
"runtime.panicdivide", "runtime.panicwrap",
"runtime.panicshift":
continue
}
// If we encountered any call, we need to keep racefunc*,
// for accurate stacktraces.
return false
case OpPanicBounds, OpPanicExtend:
// Note: these are panic generators that are ok (like the static calls above).
case OpClosureCall, OpInterCall:
// We must keep the race functions if there are any other call types.
return false
}
}
}
return true
}
// symIsRO reports whether sym is a read-only global.
func symIsRO(sym interface{}) bool {
lsym := sym.(*obj.LSym)
return lsym.Type == objabi.SRODATA && len(lsym.R) == 0
}
// read8 reads one byte from the read-only global sym at offset off.
func read8(sym interface{}, off int64) uint8 {
lsym := sym.(*obj.LSym)
if off >= int64(len(lsym.P)) || off < 0 {
// Invalid index into the global sym.
// This can happen in dead code, so we don't want to panic.
// Just return any value, it will eventually get ignored.
// See issue 29215.
return 0
}
return lsym.P[off]
}
// read16 reads two bytes from the read-only global sym at offset off.
func read16(sym interface{}, off int64, bigEndian bool) uint16 {
lsym := sym.(*obj.LSym)
if off >= int64(len(lsym.P))-1 || off < 0 {
return 0
}
if bigEndian {
return binary.BigEndian.Uint16(lsym.P[off:])
} else {
return binary.LittleEndian.Uint16(lsym.P[off:])
}
}
// read32 reads four bytes from the read-only global sym at offset off.
func read32(sym interface{}, off int64, bigEndian bool) uint32 {
lsym := sym.(*obj.LSym)
if off >= int64(len(lsym.P))-3 || off < 0 {
return 0
}
if bigEndian {
return binary.BigEndian.Uint32(lsym.P[off:])
} else {
return binary.LittleEndian.Uint32(lsym.P[off:])
}
}
// read64 reads eight bytes from the read-only global sym at offset off.
func read64(sym interface{}, off int64, bigEndian bool) uint64 {
lsym := sym.(*obj.LSym)
if off >= int64(len(lsym.P))-7 || off < 0 {
return 0
}
if bigEndian {
return binary.BigEndian.Uint64(lsym.P[off:])
} else {
return binary.LittleEndian.Uint64(lsym.P[off:])
}
}
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