Skip no-op adjustments in trans
That allows us to keep using trans_into() in case of adjustments that may actually be ignored in trans because they are a plain deref/ref pair with no overloaded deref or unsizing. Unoptimized(!) benchmarks from servo/servo#7638 Before ``` test goser::bench_clone ... bench: 17,701 ns/iter (+/- 58) = 30 MB/s test goser::bincode::bench_decoder ... bench: 33,715 ns/iter (+/- 300) = 11 MB/s test goser::bincode::bench_deserialize ... bench: 36,804 ns/iter (+/- 329) = 9 MB/s test goser::bincode::bench_encoder ... bench: 34,695 ns/iter (+/- 149) = 11 MB/s test goser::bincode::bench_populate ... bench: 18,879 ns/iter (+/- 88) test goser::bincode::bench_serialize ... bench: 31,668 ns/iter (+/- 156) = 11 MB/s test goser::capnp::bench_deserialize ... bench: 2,049 ns/iter (+/- 87) = 218 MB/s test goser::capnp::bench_deserialize_packed ... bench: 10,707 ns/iter (+/- 258) = 31 MB/s test goser::capnp::bench_populate ... bench: 635 ns/iter (+/- 5) test goser::capnp::bench_serialize ... bench: 35,657 ns/iter (+/- 155) = 12 MB/s test goser::capnp::bench_serialize_packed ... bench: 37,881 ns/iter (+/- 146) = 8 MB/s test goser::msgpack::bench_decoder ... bench: 50,634 ns/iter (+/- 307) = 5 MB/s test goser::msgpack::bench_encoder ... bench: 25,738 ns/iter (+/- 90) = 11 MB/s test goser::msgpack::bench_populate ... bench: 18,900 ns/iter (+/- 138) test goser::protobuf::bench_decoder ... bench: 2,791 ns/iter (+/- 29) = 102 MB/s test goser::protobuf::bench_encoder ... bench: 75,414 ns/iter (+/- 358) = 3 MB/s test goser::protobuf::bench_populate ... bench: 19,248 ns/iter (+/- 92) test goser::rustc_serialize_json::bench_decoder ... bench: 109,999 ns/iter (+/- 797) = 5 MB/s test goser::rustc_serialize_json::bench_encoder ... bench: 58,777 ns/iter (+/- 418) = 10 MB/s test goser::rustc_serialize_json::bench_populate ... bench: 18,887 ns/iter (+/- 76) test goser::serde_json::bench_deserializer ... bench: 104,803 ns/iter (+/- 770) = 5 MB/s test goser::serde_json::bench_populate ... bench: 18,890 ns/iter (+/- 69) test goser::serde_json::bench_serializer ... bench: 75,046 ns/iter (+/- 435) = 8 MB/s ``` After ``` test goser::bench_clone ... bench: 16,052 ns/iter (+/- 188) = 34 MB/s test goser::bincode::bench_decoder ... bench: 31,194 ns/iter (+/- 941) = 12 MB/s test goser::bincode::bench_deserialize ... bench: 33,934 ns/iter (+/- 352) = 10 MB/s test goser::bincode::bench_encoder ... bench: 30,737 ns/iter (+/- 1,969) = 13 MB/s test goser::bincode::bench_populate ... bench: 17,234 ns/iter (+/- 176) test goser::bincode::bench_serialize ... bench: 28,269 ns/iter (+/- 452) = 12 MB/s test goser::capnp::bench_deserialize ... bench: 2,019 ns/iter (+/- 85) = 221 MB/s test goser::capnp::bench_deserialize_packed ... bench: 10,662 ns/iter (+/- 527) = 31 MB/s test goser::capnp::bench_populate ... bench: 607 ns/iter (+/- 2) test goser::capnp::bench_serialize ... bench: 30,488 ns/iter (+/- 219) = 14 MB/s test goser::capnp::bench_serialize_packed ... bench: 33,731 ns/iter (+/- 201) = 9 MB/s test goser::msgpack::bench_decoder ... bench: 46,921 ns/iter (+/- 461) = 6 MB/s test goser::msgpack::bench_encoder ... bench: 22,315 ns/iter (+/- 96) = 12 MB/s test goser::msgpack::bench_populate ... bench: 17,268 ns/iter (+/- 73) test goser::protobuf::bench_decoder ... bench: 2,658 ns/iter (+/- 44) = 107 MB/s test goser::protobuf::bench_encoder ... bench: 71,024 ns/iter (+/- 359) = 4 MB/s test goser::protobuf::bench_populate ... bench: 17,704 ns/iter (+/- 104) test goser::rustc_serialize_json::bench_decoder ... bench: 107,867 ns/iter (+/- 759) = 5 MB/s test goser::rustc_serialize_json::bench_encoder ... bench: 52,327 ns/iter (+/- 479) = 11 MB/s test goser::rustc_serialize_json::bench_populate ... bench: 17,262 ns/iter (+/- 68) test goser::serde_json::bench_deserializer ... bench: 99,156 ns/iter (+/- 657) = 6 MB/s test goser::serde_json::bench_populate ... bench: 17,264 ns/iter (+/- 77) test goser::serde_json::bench_serializer ... bench: 66,135 ns/iter (+/- 392) = 9 MB/s ```
This commit is contained in:
Björn Steinbrink
parent
cff0411706
commit
2c17bfc20c
2 changed files with 41 additions and 1 deletions
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@ -119,7 +119,7 @@ pub fn trans_into<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
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debuginfo::set_source_location(bcx.fcx, expr.id, expr.span);
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if bcx.tcx().tables.borrow().adjustments.contains_key(&expr.id) {
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if adjustment_required(bcx, expr) {
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// use trans, which may be less efficient but
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// which will perform the adjustments:
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let datum = unpack_datum!(bcx, trans(bcx, expr));
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@ -334,6 +334,37 @@ pub fn unsized_info<'ccx, 'tcx>(ccx: &CrateContext<'ccx, 'tcx>,
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}
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}
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fn adjustment_required<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
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expr: &hir::Expr) -> bool {
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let adjustment = match bcx.tcx().tables.borrow().adjustments.get(&expr.id).cloned() {
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None => { return false; }
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Some(adj) => adj
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};
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// Don't skip a conversion from Box<T> to &T, etc.
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if bcx.tcx().is_overloaded_autoderef(expr.id, 0) {
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return true;
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}
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match adjustment {
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AdjustReifyFnPointer => {
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// FIXME(#19925) once fn item types are
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// zero-sized, we'll need to return true here
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false
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}
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AdjustUnsafeFnPointer => {
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// purely a type-level thing
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false
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}
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AdjustDerefRef(ref adj) => {
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// We are a bit paranoid about adjustments and thus might have a re-
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// borrow here which merely derefs and then refs again (it might have
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// a different region or mutability, but we don't care here).
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!(adj.autoderefs == 1 && adj.autoref.is_some() && adj.unsize.is_none())
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}
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}
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}
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/// Helper for trans that apply adjustments from `expr` to `datum`, which should be the unadjusted
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/// translation of `expr`.
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fn apply_adjustments<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
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@ -26,3 +26,12 @@ pub fn no_op_slice_adjustment(x: &[u8]) -> &[u8] {
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// CHECK: call void @llvm.memcpy.{{.*}}(i8* [[DST]], i8* [[SRC]],
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{ x }
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}
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// CHECK-LABEL: @no_op_slice_adjustment2
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#[no_mangle]
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pub fn no_op_slice_adjustment2(x: &[u8]) -> &[u8] {
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// We used to generate an extra alloca and memcpy for the function's return value, so check
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// that there's no memcpy (the slice is written to sret_slot element-wise)
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// CHECK-NOT: call void @llvm.memcpy.
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no_op_slice_adjustment(x)
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}
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