diff options
Diffstat (limited to 'src/cmd/compile/internal/gc/sparselocatephifunctions.go')
| -rw-r--r-- | src/cmd/compile/internal/gc/sparselocatephifunctions.go | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/src/cmd/compile/internal/gc/sparselocatephifunctions.go b/src/cmd/compile/internal/gc/sparselocatephifunctions.go index e15f22123f..43cc50bd92 100644 --- a/src/cmd/compile/internal/gc/sparselocatephifunctions.go +++ b/src/cmd/compile/internal/gc/sparselocatephifunctions.go @@ -153,10 +153,13 @@ func (s *state) locatePotentialPhiFunctions(fn *Node) *sparseDefState { p := e.Block() dm.Use(t, p) // always count phi pred as "use"; no-op except for loop edges, which matter. x := t.stm.Find(p, ssa.AdjustAfter, helper) // Look for defs reaching or within predecessors. + if x == nil { // nil def from a predecessor means a backedge that will be visited soon. + continue + } if defseen == nil { defseen = x } - if defseen != x || x == nil { // TODO: too conservative at loops, does better if x == nil -> continue + if defseen != x { // Need to insert a phi function here because predecessors's definitions differ. change = true // Phi insertion is at AdjustBefore, visible with find in same block at AdjustWithin or AdjustAfter. |