Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

cmd/compile/internal/ssa: use math/bits for register sets

Browse source 
Using bits.TrailingZeroes instead of iterating over each bit is a small
but easy win for the common case of only one or two registers being set.

I copied in the implementation for use with pre-1.9 bootstraps.

Change-Id: Ieaa768554d7d5239a5617fbf34f1ee0b32ce1de5
Reviewed-on: https://go-review.googlesource.com/92395
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Heschi Kreinick 2018-01-29 16:09:11 -05:00
parent 39eea62340
commit 7ac756f74b
3 changed files with 86 additions and 35 deletions
Download patch file Download diff file Expand all files Collapse all files

84
src/cmd/compile/internal/ssa/debug.go
View file

@ -70,10 +70,16 @@ func (state *stateAtPC) reset(live []liveSlot) {
if live.loc.Registers == 0 {
continue
}
for reg, regMask := 0, 1; reg < len(registers); reg, regMask = reg+1, regMask<<1 {
if live.loc.Registers&RegisterSet(regMask) != 0 {
registers[reg] = append(registers[reg], SlotID(live.slot))
mask := uint64(live.loc.Registers)
for {
if mask == 0 {
break
}
reg := uint8(TrailingZeros64(mask))
mask &^= 1 << reg
registers[reg] = append(registers[reg], SlotID(live.slot))
}
}
state.slots, state.registers = slots, registers
@ -90,10 +96,14 @@ func (b *BlockDebug) LocString(loc VarLoc) string {
storage = append(storage, "stack")
}
for reg := 0; reg < 64; reg++ {
if loc.Registers&(1<<uint8(reg)) == 0 {
continue
mask := uint64(loc.Registers)
for {
if mask == 0 {
break
}
reg := uint8(TrailingZeros64(mask))
mask &^= 1 << reg
if registers != nil {
storage = append(storage, registers[reg].String())
} else {
@ -513,10 +523,15 @@ func (state *debugState) mergePredecessors(b *Block, blockLocs []*BlockDebug) *B
if slotLoc.Registers == 0 {
continue
}
for reg, regMask := 0, 1; reg < len(state.registers); reg, regMask = reg+1, regMask<<1 {
if slotLoc.Registers&RegisterSet(regMask) != 0 {
state.currentState.registers[reg] = append(state.currentState.registers[reg], SlotID(slotID))
mask := uint64(slotLoc.Registers)
for {
if mask == 0 {
break
}
reg := uint8(TrailingZeros64(mask))
mask &^= 1 << reg
state.currentState.registers[reg] = append(state.currentState.registers[reg], SlotID(slotID))
}
}
result.startState = state.cache.GetLiveSlotSlice()
@ -539,28 +554,29 @@ func (state *debugState) processValue(v *Value, vSlots []SlotID, vReg *Register)
// Handle any register clobbering. Call operations, for example,
// clobber all registers even though they don't explicitly write to
// them.
if clobbers := opcodeTable[v.Op].reg.clobbers; clobbers != 0 {
for reg := 0; reg < len(state.registers); reg++ {
if clobbers&(1<<uint8(reg)) == 0 {
clobbers := uint64(opcodeTable[v.Op].reg.clobbers)
for {
if clobbers == 0 {
break
}
reg := uint8(TrailingZeros64(clobbers))
clobbers &^= 1 << reg
for _, slot := range locs.registers[reg] {
if state.loggingEnabled {
state.logf("at %v: %v clobbered out of %v\n", v.ID, state.slots[slot], &state.registers[reg])
}
last := locs.slots[slot]
if last.absent() {
state.f.Fatalf("at %v: slot %v in register %v with no location entry", v, state.slots[slot], &state.registers[reg])
continue
}
for _, slot := range locs.registers[reg] {
if state.loggingEnabled {
state.logf("at %v: %v clobbered out of %v\n", v.ID, state.slots[slot], &state.registers[reg])
}
last := locs.slots[slot]
if last.absent() {
state.f.Fatalf("at %v: slot %v in register %v with no location entry", v, state.slots[slot], &state.registers[reg])
continue
}
regs := last.Registers &^ (1 << uint8(reg))
setSlot(slot, VarLoc{regs, last.OnStack, last.StackOffset})
}
locs.registers[reg] = locs.registers[reg][:0]
regs := last.Registers &^ (1 << uint8(reg))
setSlot(slot, VarLoc{regs, last.OnStack, last.StackOffset})
}
locs.registers[reg] = locs.registers[reg][:0]
}
switch {
@ -692,14 +708,12 @@ func canMerge(pending, new VarLoc) bool {
// firstReg returns the first register in set that is present.
func firstReg(set RegisterSet) uint8 {
for reg := 0; reg < 64; reg++ {
if set&(1<<uint8(reg)) != 0 {
return uint8(reg)
}
if set == 0 {
// This is wrong, but there seem to be some situations where we
// produce locations with no storage.
return 0
}
// This is wrong, but there seem to be some situations where we
// produce locations with no storage.
return 0
return uint8(TrailingZeros64(uint64(set)))
}
// buildLocationLists builds location lists for all the user variables in