Cheng Shao pushed to branch wip/wasm-remove-webkit-workaround at Glasgow Haskell Compiler / GHC Commits: 34e976ac by Cheng Shao at 2026-07-28T10:28:05+02:00 Revert "wasm: workaround WebKit bug in dyld" This reverts commit c9b8465c2c338176fcab9d197e9d31f4aee11f68. The underlying webkit bug has been fixed in https://commits.webkit.org/314219@main. Closes #27564. - - - - - 1 changed file: - utils/jsffi/dyld.mjs Changes: ===================================== utils/jsffi/dyld.mjs ===================================== @@ -783,25 +783,7 @@ class DyLD { // Wasm memory & table #memory = new WebAssembly.Memory({ initial: 1 }); - #table = new WebAssembly.Table({ element: "anyfunc", initial: 1 }); - // First free slot, might be invalid when it advances to #table.length - #tableFree = 1; - // See Note [The evil wasm table grower] - #tableGrowInstance = new WebAssembly.Instance( - new WebAssembly.Module( - new Uint8Array([ - 0, 97, 115, 109, 1, 0, 0, 0, 1, 6, 1, 96, 1, 127, 1, 127, 2, 35, 1, 3, - 101, 110, 118, 25, 95, 95, 105, 110, 100, 105, 114, 101, 99, 116, 95, - 102, 117, 110, 99, 116, 105, 111, 110, 95, 116, 97, 98, 108, 101, 1, - 112, 0, 0, 3, 2, 1, 0, 7, 31, 1, 27, 95, 95, 103, 104, 99, 95, 119, 97, - 115, 109, 95, 106, 115, 102, 102, 105, 95, 116, 97, 98, 108, 101, 95, - 103, 114, 111, 119, 0, 0, 10, 11, 1, 9, 0, 208, 112, 32, 0, 252, 15, 0, - 11, - ]) - ), - { env: { __indirect_function_table: this.#table } } - ); // __stack_pointer #sp = new WebAssembly.Global( @@ -846,82 +828,6 @@ class DyLD { // Global STG registers #regs = {}; - // Note [The evil wasm table grower] - // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - // We need to grow the wasm table as we load shared libraries in - // wasm dyld. We used to directly call the table.grow() JS API, - // which works as expected in Firefox/Chrome, but unfortunately, - // WebKit's implementation of the table.grow() JS API is broken: - // https://bugs.webkit.org/show_bug.cgi?id=290681, which means that - // the wasm dyld simply does not work in WebKit-based browsers like - // Safari. - // - // Now, one simple workaround would be to avoid growing the table at - // all: just allocate a huge table upfront (current limitation - // agreed by all vendors is 10000000). To avoid unnecessary space - // waste on non-WebKit platforms, we could additionally check - // navigator.userAgent against some regexes and only allocate - // fixed-length table when there's no blink/gecko mention. But this - // is fragile and gross, and it's better to stick to a uniform code - // path for all browsers. - // - // Fortunately, it turns out the table.grow wasm instruction work as - // expected in WebKit! So we can invoke a wasm function that grows - // the table for us. But don't open a champagne yet, where would - // that wasm function come from? It can't be put into RTS, or even - // libc.so, because loading those libraries would require growing - // the table in the first place! Or perhaps, reserve a table upfront - // that's just large enough to load RTS and then we can access that - // function for subsequent table grows? But then we need to - // experiment for a reasonable initial size, and add a magic number - // here, which is also fragile and gross and not future-proof! - // - // So this special wasm function needs to live in a single wasm - // module, which is loaded before we load anything else. The full - // source code for this module is: - // - // (module - // (type (func (param i32) (result i32))) - // (import "env" "__indirect_function_table" (table 0 funcref)) - // (export "__ghc_wasm_jsffi_table_grow" (func 0)) - // (func (type 0) (param i32) (result i32) - // ref.null func - // local.get 0 - // table.grow 0 - // ) - // ) - // - // This module is 103 bytes so that we can inline its blob in dyld, - // and use the usually discouraged synchronous - // WebAssembly.Instance/WebAssembly.Module constructors to load it. - // On non-WebKit platforms, growing tables this way would introduce - // a bit of extra JS/Wasm interop overhead, which can be amplified - // as we used to call table.grow(1, foo) for every GOT.func item. - // Therefore, unless we're about to exceed the hard limit of table - // size, we now grow the table exponentially, and use bump - // allocation to calculate the table index to be returned. - // Exponential growth is only implemented to minimize the JS/Wasm - // interop overhead when calling __ghc_wasm_jsffi_table_grow; - // V8/SpiderMonkey/WebKit already do their own exponential growth of - // the table's backing buffer in their table growth logic. - // - // Invariants: n >= 0; when v is non-null, n === 1 - #tableGrow(n, v) { - const prev_free = this.#tableFree; - if (prev_free + n > this.#table.length) { - const min_delta = prev_free + n - this.#table.length; - const delta = Math.max(min_delta, this.#table.length); - this.#tableGrowInstance.exports.__ghc_wasm_jsffi_table_grow( - this.#table.length + delta <= 10000000 ? delta : min_delta - ); - } - if (v) { - this.#table.set(prev_free, v); - } - this.#tableFree += n; - return prev_free; - } - constructor({ args, rpc }) { this.#rpc = rpc; @@ -1116,7 +1022,7 @@ class DyLD { // __memory_base & __table_base, different for each .so let memory_base; - let table_base = this.#tableGrow(tableSize); + let table_base = this.#table.grow(tableSize); console.assert(tableP2Align === 0); // libc.so is always the first one to be ever loaded and has VIP @@ -1220,7 +1126,7 @@ class DyLD { if (this.exportFuncs[name]) { this.#gotFunc[name] = new WebAssembly.Global( { value: "i32", mutable: true }, - this.#tableGrow(1, this.exportFuncs[name]) + this.#table.grow(1, this.exportFuncs[name]) ); continue; } @@ -1271,7 +1177,7 @@ class DyLD { if (this.#gotFunc[k]) { const got = this.#gotFunc[k]; if (got.value === DyLD.#poison) { - const idx = this.#tableGrow(1, v); + const idx = this.#table.grow(1, v); got.value = idx; } else { this.#table.set(got.value, v); @@ -1325,7 +1231,7 @@ class DyLD { // Not in GOT.func yet, create the entry on demand if (this.exportFuncs[sym]) { console.assert(!this.#gotFunc[sym]); - const addr = this.#tableGrow(1, this.exportFuncs[sym]); + const addr = this.#table.grow(1, this.exportFuncs[sym]); this.#gotFunc[sym] = new WebAssembly.Global( { value: "i32", mutable: true }, addr View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/34e976ac2d43cff61cf6f9daa47d8811... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/34e976ac2d43cff61cf6f9daa47d8811... 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