diff options
| author | David Chase <drchase@google.com> | 2025-09-17 17:21:37 -0400 |
|---|---|---|
| committer | Cherry Mui <cherryyz@google.com> | 2025-10-03 12:31:36 -0700 |
| commit | 1bca4c1673f5d90822086f34aed6de4a9bea2d93 (patch) | |
| tree | 1a9bef23f40086918a5687e7041ab8e6a21cf8eb /src/cmd/compile/internal | |
| parent | 38b26f29f1f97d24afc852b9f4eee829341ee682 (diff) | |
| download | go-1bca4c1673f5d90822086f34aed6de4a9bea2d93.tar.xz | |
cmd/compile: improve slicemask removal
this will be subsumed by pending changes in local slice
representation, however this was easy and works well.
Cherry-picked from the dev.simd branch. This CL is not
necessarily SIMD specific. Apply early to reduce risk.
Change-Id: I5b6eb10d257f04f906be7a8a6f2b6833992a39e8
Reviewed-on: https://go-review.googlesource.com/c/go/+/704876
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/708866
Reviewed-by: David Chase <drchase@google.com>
Diffstat (limited to 'src/cmd/compile/internal')
| -rw-r--r-- | src/cmd/compile/internal/ssa/prove.go | 30 |
1 files changed, 22 insertions, 8 deletions
diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go index 5ed5be4744..b4f91fd4fd 100644 --- a/src/cmd/compile/internal/ssa/prove.go +++ b/src/cmd/compile/internal/ssa/prove.go @@ -2529,24 +2529,38 @@ func simplifyBlock(sdom SparseTree, ft *factsTable, b *Block) { switch v.Op { case OpSlicemask: // Replace OpSlicemask operations in b with constants where possible. - x, delta := isConstDelta(v.Args[0]) - if x == nil { + cap := v.Args[0] + x, delta := isConstDelta(cap) + if x != nil { + // slicemask(x + y) + // if x is larger than -y (y is negative), then slicemask is -1. + lim := ft.limits[x.ID] + if lim.umin > uint64(-delta) { + if cap.Op == OpAdd64 { + v.reset(OpConst64) + } else { + v.reset(OpConst32) + } + if b.Func.pass.debug > 0 { + b.Func.Warnl(v.Pos, "Proved slicemask not needed") + } + v.AuxInt = -1 + } break } - // slicemask(x + y) - // if x is larger than -y (y is negative), then slicemask is -1. - lim := ft.limits[x.ID] - if lim.umin > uint64(-delta) { - if v.Args[0].Op == OpAdd64 { + lim := ft.limits[cap.ID] + if lim.umin > 0 { + if cap.Type.Size() == 8 { v.reset(OpConst64) } else { v.reset(OpConst32) } if b.Func.pass.debug > 0 { - b.Func.Warnl(v.Pos, "Proved slicemask not needed") + b.Func.Warnl(v.Pos, "Proved slicemask not needed (by limit)") } v.AuxInt = -1 } + case OpCtz8, OpCtz16, OpCtz32, OpCtz64: // On some architectures, notably amd64, we can generate much better // code for CtzNN if we know that the argument is non-zero. |