diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/cmd/compile/internal/ssa/prove.go | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go index 93bd525c38..8fe1bb7050 100644 --- a/src/cmd/compile/internal/ssa/prove.go +++ b/src/cmd/compile/internal/ssa/prove.go @@ -5,6 +5,7 @@ package ssa import ( + "cmd/compile/internal/types" "cmd/internal/src" "fmt" "math" @@ -2132,6 +2133,21 @@ func addRestrictions(parent *Block, ft *factsTable, t domain, v, w *Value, r rel } } +func unsignedAddOverflows(a, b uint64, t *types.Type) bool { + switch t.Size() { + case 8: + return a+b < a + case 4: + return a+b > math.MaxUint32 + case 2: + return a+b > math.MaxUint16 + case 1: + return a+b > math.MaxUint8 + default: + panic("unreachable") + } +} + func addLocalFacts(ft *factsTable, b *Block) { // Propagate constant ranges among values in this block. // We do this before the second loop so that we have the @@ -2151,6 +2167,21 @@ func addLocalFacts(ft *factsTable, b *Block) { // FIXME(go.dev/issue/68857): this loop only set up limits properly when b.Values is in topological order. // flowLimit can also depend on limits given by this loop which right now is not handled. switch v.Op { + case OpAdd64, OpAdd32, OpAdd16, OpAdd8: + x := ft.limits[v.Args[0].ID] + y := ft.limits[v.Args[1].ID] + if !unsignedAddOverflows(x.umax, y.umax, v.Type) { + r := gt + if !x.nonzero() { + r |= eq + } + ft.update(b, v, v.Args[1], unsigned, r) + r = gt + if !y.nonzero() { + r |= eq + } + ft.update(b, v, v.Args[0], unsigned, r) + } case OpAnd64, OpAnd32, OpAnd16, OpAnd8: ft.update(b, v, v.Args[0], unsigned, lt|eq) ft.update(b, v, v.Args[1], unsigned, lt|eq) |