diff options
Diffstat (limited to 'src/cmd')
| -rw-r--r-- | src/cmd/compile/internal/ssa/sccp.go | 30 |
1 files changed, 23 insertions, 7 deletions
diff --git a/src/cmd/compile/internal/ssa/sccp.go b/src/cmd/compile/internal/ssa/sccp.go index 7ef8d6b7c1..3793e9f86a 100644 --- a/src/cmd/compile/internal/ssa/sccp.go +++ b/src/cmd/compile/internal/ssa/sccp.go @@ -50,6 +50,7 @@ type lattice struct { type worklist struct { f *Func // the target function to be optimized out edges []Edge // propagate constant facts through edges + inUses *sparseSet // IDs already in uses, for duplicate check uses []*Value // re-visiting set visited map[Edge]bool // visited edges latticeCells map[*Value]lattice // constant lattices @@ -71,6 +72,8 @@ func sccp(f *Func) { t.defBlock = make(map[*Value][]*Block) t.latticeCells = make(map[*Value]lattice) t.visitedBlock = f.Cache.allocBoolSlice(f.NumBlocks()) + t.inUses = f.newSparseSet(f.NumValues()) + defer f.retSparseSet(t.inUses) defer f.Cache.freeBoolSlice(t.visitedBlock) // build it early since we rely heavily on the def-use chain later @@ -104,6 +107,7 @@ func sccp(f *Func) { if len(t.uses) > 0 { use := t.uses[0] t.uses = t.uses[1:] + t.inUses.remove(use.ID) t.visitValue(use) continue } @@ -251,6 +255,10 @@ func (t *worklist) buildDefUses() { for _, arg := range val.Args { // find its uses, only uses that can become constants take into account if possibleConst(arg) && possibleConst(val) { + // Phi may refer to itself as uses, avoid duplicate visits + if arg == val { + continue + } if _, exist := t.defUse[arg]; !exist { t.defUse[arg] = make([]*Value, 0, arg.Uses) } @@ -270,12 +278,16 @@ func (t *worklist) buildDefUses() { // addUses finds all uses of value and appends them into work list for further process func (t *worklist) addUses(val *Value) { for _, use := range t.defUse[val] { - if val == use { - // Phi may refer to itself as uses, ignore them to avoid re-visiting phi - // for performance reason + // Provenly not a constant, ignore + useLt := t.getLatticeCell(use) + if useLt.tag == bottom { continue } - t.uses = append(t.uses, use) + // Avoid duplicate visits + if !t.inUses.contains(use.ID) { + t.inUses.add(use.ID) + t.uses = append(t.uses, use) + } } for _, block := range t.defBlock[val] { if t.visitedBlock[block.ID] { @@ -362,15 +374,19 @@ func computeLattice(f *Func, val *Value, args ...*Value) lattice { } func (t *worklist) visitValue(val *Value) { + // Impossible to be a constant, fast fail if !possibleConst(val) { - // fast fail for always worst Values, i.e. there is no lowering happen - // on them, their lattices must be initially worse Bottom. return } + // Provenly not a constant, fast fail oldLt := t.getLatticeCell(val) + if oldLt.tag == bottom { + return + } + + // Re-visit all uses of value if its lattice is changed defer func() { - // re-visit all uses of value if its lattice is changed newLt := t.getLatticeCell(val) if !equals(newLt, oldLt) { if oldLt.tag > newLt.tag { |