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| author | Giovanni Bajo <rasky@develer.com> | 2018-03-13 00:25:06 +0100 |
|---|---|---|
| committer | Giovanni Bajo <rasky@develer.com> | 2018-03-24 03:06:21 +0000 |
| commit | d54902ece907d55d937b7b2fa294e0cc22b57a32 (patch) | |
| tree | 79c6b8bd3d130360392daadad41865d992182c3d /src | |
| parent | 385d936fb287cfe3a491ced2d77d52d71b7705a8 (diff) | |
| download | go-d54902ece907d55d937b7b2fa294e0cc22b57a32.tar.xz | |
cmd/compile: in prove, shortcircuit self-facts
Sometimes, we can end up calling update with a self-relation
about a variable (x REL x). In this case, there is no need
to record anything: the relation is unsatisfiable if and only
if it doesn't contain eq.
This also helps avoiding infinite loop in next CL that will
introduce transitive closure of relations.
Passes toolstash -cmp.
Change-Id: Ic408452ec1c13653f22ada35466ec98bc14aaa8e
Reviewed-on: https://go-review.googlesource.com/100276
Reviewed-by: Austin Clements <austin@google.com>
Diffstat (limited to 'src')
| -rw-r--r-- | src/cmd/compile/internal/ssa/prove.go | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go index ec31d46d02..cf0118ac3c 100644 --- a/src/cmd/compile/internal/ssa/prove.go +++ b/src/cmd/compile/internal/ssa/prove.go @@ -193,6 +193,15 @@ func (ft *factsTable) update(parent *Block, v, w *Value, d domain, r relation) { return } + // Self-fact. It's wasteful to register it into the facts + // table, so just note whether it's satisfiable + if v == w { + if r&eq == 0 { + ft.unsat = true + } + return + } + if lessByID(w, v) { v, w = w, v r = reverseBits[r] |