diff options
| author | Jorropo <jorropo.pgm@gmail.com> | 2025-07-04 09:21:03 +0200 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2025-07-24 13:48:55 -0700 |
| commit | e5f202bb60b246a7aee2a14b95ca399fd243accd (patch) | |
| tree | 9a6f3181744e236d5c81cb8a8324e3a494aaf9cc /src | |
| parent | bd80f74bc154585237a3c1b636e30dab6d781923 (diff) | |
| download | go-e5f202bb60b246a7aee2a14b95ca399fd243accd.tar.xz | |
cmd/compile: learn transitive proofs for safe unsigned adds
I've split this into it's own CL to make git bisect more effective.
Change-Id: Iaab5f0bd2ad51e86ced8c6b8fbd371eb75eeef14
Reviewed-on: https://go-review.googlesource.com/c/go/+/685815
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Mark Freeman <mark@golang.org>
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) |