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* Wasm tests: add typed-funcref test showing example of desirable optimizations. In order to have fast IC (inline cache) chains in AOT-compiled dynamic language Wasms, it would be great if we could make the "call to a typed funcref at a constant table index" pattern fast. This use-case was discussed at the most recent Wasmtime biweekly and @jameysharp is working on some optimizations; the intent of this PR is to provide a concrete test-case whose blessed output we can see improve over time. In particular, the following opts are still desirable: - With the use of non-nullable typed funcrefs, there shouldn't be a null check (there currently is, as noted by a comment in the code due to lack of type information at the right spot). - With the use of a constant table size and a constant index to the `table.get`, we should be able to load from the table without a bounds-check or any Spectre masking. Other further optimizations for this pattern might be possible if we rearrange the table and function-reference data structures, and the lazy-initialization scheme thereof, but the above should be agnostic to that. * Add comments to clarify typed funcrefs usage.pull/8161/head
Chris Fallin
8 months ago
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1 changed files with 166 additions and 0 deletions
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;;! target = "x86_64" |
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;;! test = "optimize" |
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;;! flags = [ "-Wfunction-references=y" ] |
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;; This test is meant to simulate how typed funcrefs in a table may be |
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;; used for ICs (inline caches) in a Wasm module compiled from a dynamic |
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;; language. In native JIT engines, IC chains have head pointers that |
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;; are raw code pointers and IC-using code can call each with a few ops |
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;; (load pointer, call indirect). We'd like similar efficiency by |
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;; storing funcrefs for the first IC in each chain in a typed-funcref |
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;; table. |
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(module |
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(type $ic-stub (func (param i32 i32 i32 i32) (result i32))) |
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;; This syntax declares a table that is exactly 100 elements, whose |
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;; elements are non-nullable function references, and whose default |
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;; value (needed because non-nullable) is a pointer to `$ic1`. |
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(table $ic-sites 100 100 (ref $ic-stub) (ref.func $ic1)) |
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(func $ic1 (param i32 i32 i32 i32) (result i32) |
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local.get 0) |
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(func $call-ics (param i32 i32 i32 i32) (result i32) |
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(local $sum i32) |
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;; IC callsite index 1 (arbitrary). |
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local.get 0 |
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local.get 1 |
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local.get 2 |
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local.get 3 |
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i32.const 1 |
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table.get $ic-sites |
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call_ref $ic-stub |
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local.get $sum |
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i32.add |
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local.set $sum |
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;; IC callsite index 2 (arbitrary). |
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local.get 0 |
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local.get 1 |
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local.get 2 |
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local.get 3 |
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i32.const 2 |
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table.get $ic-sites |
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call_ref $ic-stub |
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local.get $sum |
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i32.add |
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local.set $sum |
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local.get $sum)) |
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;; function u0:0(i64 vmctx, i64, i32, i32, i32, i32) -> i32 fast { |
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;; gv0 = vmctx |
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;; gv1 = load.i64 notrap aligned readonly gv0+8 |
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;; gv2 = load.i64 notrap aligned gv1 |
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;; sig0 = (i64 vmctx, i32 uext, i32 uext) -> i32 uext system_v |
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;; sig1 = (i64 vmctx, i32 uext) -> i32 uext system_v |
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;; stack_limit = gv2 |
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;; |
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;; block0(v0: i64, v1: i64, v2: i32, v3: i32, v4: i32, v5: i32): |
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;; v6 -> v2 |
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;; @002c jump block1 |
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;; |
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;; block1: |
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;; @002c return v2 |
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;; } |
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;; |
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;; function u0:1(i64 vmctx, i64, i32, i32, i32, i32) -> i32 fast { |
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;; gv0 = vmctx |
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;; gv1 = load.i64 notrap aligned readonly gv0+8 |
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;; gv2 = load.i64 notrap aligned gv1 |
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;; gv3 = vmctx |
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;; gv4 = load.i64 notrap aligned gv3+72 |
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;; sig0 = (i64 vmctx, i32 uext, i32 uext) -> i64 system_v |
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;; sig1 = (i64 vmctx, i64, i32, i32, i32, i32) -> i32 fast |
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;; sig2 = (i64 vmctx, i32 uext, i32 uext) -> i32 uext system_v |
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;; sig3 = (i64 vmctx, i32 uext) -> i32 uext system_v |
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;; stack_limit = gv2 |
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;; |
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;; block0(v0: i64, v1: i64, v2: i32, v3: i32, v4: i32, v5: i32): |
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;; v21 -> v0 |
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;; v47 -> v0 |
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;; v56 -> v0 |
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;; v59 -> v0 |
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;; v30 -> v2 |
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;; v31 -> v3 |
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;; v32 -> v4 |
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;; v33 -> v5 |
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;; v62 = iconst.i8 0 |
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;; @003b brif v62, block6, block7 ; v62 = 0 |
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;; |
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;; block6 cold: |
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;; @003b trap table_oob |
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;; |
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;; block7: |
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;; @003b v12 = load.i64 notrap aligned v0+72 |
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;; v79 = iconst.i8 0 |
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;; v70 = iconst.i64 8 |
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;; @003b v14 = iadd v12, v70 ; v70 = 8 |
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;; @003b v16 = select_spectre_guard v79, v12, v14 ; v79 = 0 |
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;; @003b v17 = load.i64 notrap aligned table v16 |
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;; v58 = iconst.i64 -2 |
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;; @003b v18 = band v17, v58 ; v58 = -2 |
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;; @003b brif v17, block3(v18), block2 |
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;; |
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;; block2 cold: |
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;; @004e v48 = load.i64 notrap aligned readonly v0+56 |
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;; @004e v49 = load.i64 notrap aligned readonly v48+72 |
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;; @002f v7 = iconst.i32 0 |
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;; v28 -> v7 |
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;; @0039 v8 = iconst.i32 1 |
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;; @003b v24 = call_indirect sig0, v49(v0, v7, v8) ; v7 = 0, v8 = 1 |
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;; @003b jump block3(v24) |
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;; |
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;; block3(v19: i64): |
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;; @003d brif v19, block9, block8 |
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;; |
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;; block8 cold: |
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;; @003d trap null_reference |
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;; |
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;; block9: |
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;; @003d v25 = load.i64 notrap aligned readonly v19+16 |
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;; @003d v26 = load.i64 notrap aligned readonly v19+32 |
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;; @003d v27 = call_indirect sig1, v25(v26, v0, v2, v3, v4, v5) |
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;; v80 = iconst.i8 0 |
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;; @004e brif v80, block10, block11 ; v80 = 0 |
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;; |
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;; block10 cold: |
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;; @004e trap table_oob |
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;; |
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;; block11: |
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;; @004e v38 = load.i64 notrap aligned v0+72 |
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;; v81 = iconst.i8 0 |
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;; v78 = iconst.i64 16 |
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;; @004e v40 = iadd v38, v78 ; v78 = 16 |
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;; @004e v42 = select_spectre_guard v81, v38, v40 ; v81 = 0 |
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;; @004e v43 = load.i64 notrap aligned table v42 |
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;; v82 = iconst.i64 -2 |
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;; v83 = band v43, v82 ; v82 = -2 |
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;; @004e brif v43, block5(v83), block4 |
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;; |
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;; block4 cold: |
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;; v84 = load.i64 notrap aligned readonly v0+56 |
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;; v85 = load.i64 notrap aligned readonly v84+72 |
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;; v86 = iconst.i32 0 |
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;; @004c v34 = iconst.i32 2 |
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;; @004e v50 = call_indirect sig0, v85(v0, v86, v34) ; v86 = 0, v34 = 2 |
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;; @004e jump block5(v50) |
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;; |
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;; block5(v45: i64): |
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;; @0050 brif v45, block13, block12 |
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;; |
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;; block12 cold: |
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;; @0050 trap null_reference |
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;; |
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;; block13: |
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;; @0050 v51 = load.i64 notrap aligned readonly v45+16 |
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;; @0050 v52 = load.i64 notrap aligned readonly v45+32 |
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;; @0050 v53 = call_indirect sig1, v51(v52, v0, v2, v3, v4, v5) |
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;; @0059 jump block1 |
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;; |
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;; block1: |
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;; @0054 v55 = iadd.i32 v53, v27 |
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;; v6 -> v55 |
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;; @0059 return v55 |
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;; } |
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