From 4e204b42f5b66ea36f0421098a42addc7c2ba6c7 Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Mon, 13 Jul 2015 23:52:59 -0700 Subject: [PATCH] [dev.ssa] cmd/compile/internal/ssa: ensure Phi ops are scheduled first Phi ops should always be scheduled first. They have the semantics of all happening simultaneously at the start of the block. The regalloc phase assumes all the phis will appear first. Change-Id: I30291e1fa384a0819205218f1d1ec3aef6d538dd Reviewed-on: https://go-review.googlesource.com/12154 Reviewed-by: Josh Bleecher Snyder --- src/cmd/compile/internal/ssa/schedule.go | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/src/cmd/compile/internal/ssa/schedule.go b/src/cmd/compile/internal/ssa/schedule.go index 60d2cd5460..15e8ace391 100644 --- a/src/cmd/compile/internal/ssa/schedule.go +++ b/src/cmd/compile/internal/ssa/schedule.go @@ -54,16 +54,28 @@ func schedule(f *Func) { } } - // Topologically sort the values in b. order = order[:0] + + // Schedule phis first for _, v := range b.Values { - if v == b.Control { + if v.Op == OpPhi { + // TODO: what if a phi is also a control op? It happens for + // mem ops all the time, which shouldn't matter. But for + // regular ops we might be violating invariants about where + // control ops live. + if v == b.Control && !v.Type.IsMemory() { + f.Unimplementedf("phi is a control op %s %s", v, b) + } + order = append(order, v) + } + } + + // Topologically sort the non-phi values in b. + for _, v := range b.Values { + if v.Op == OpPhi { continue } - if v.Op == OpPhi { - // Phis all go first. We handle phis specially - // because they may have self edges "a = phi(a, b, c)" - order = append(order, v) + if v == b.Control { continue } if state[v.ID] != unmarked {