diff --git a/lld/docs/WebAssembly.rst b/lld/docs/WebAssembly.rst --- a/lld/docs/WebAssembly.rst +++ b/lld/docs/WebAssembly.rst @@ -39,6 +39,10 @@ Export all symbols (normally combined with --no-gc-sections) + Note that this will not export linker-generated mutable globals unless + the resulting binaryen already includes the 'mutable-globals' features + since that would otherwise create and invalid binaryen. + .. option:: --export-dynamic When building an executable, export any non-hidden symbols. By default only diff --git a/lld/test/wasm/mutable-global-exports.s b/lld/test/wasm/mutable-global-exports.s new file mode 100644 --- /dev/null +++ b/lld/test/wasm/mutable-global-exports.s @@ -0,0 +1,88 @@ +# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s +# +# Should fail without mutable globals feature enabled. +# RUN: not wasm-ld --export-all %t.o -o %t.wasm 2>&1 | FileCheck -check-prefix=CHECK-ERR %s +# RUN: not wasm-ld --export=foo_global %t.o -o %t.wasm 2>&1 | FileCheck -check-prefix=CHECK-ERR %s +# +# RUN: wasm-ld --features=mutable-globals --export=foo_global %t.o -o %t.wasm +# RUN: obj2yaml %t.wasm | FileCheck %s + +# Explcitly check that __stack_pointer can be exported +# RUN: wasm-ld --features=mutable-globals --export=__stack_pointer %t.o -o %t.wasm +# RUN: obj2yaml %t.wasm | FileCheck -check-prefix=CHECK-SP %s + +# RUN: wasm-ld --features=mutable-globals --export-all %t.o -o %t.wasm +# RUN: obj2yaml %t.wasm | FileCheck -check-prefix=CHECK-ALL %s + + +.globl _start +.globl foo_global + +.globaltype foo_global, i32 +foo_global: + +_start: + .functype _start () -> () + end_function + +# CHECK-ERR: mutable global exported but 'mutable-globals' feature not present in inputs: `foo_global`. Use --no-check-features to suppress + +# CHECK: - Type: EXPORT +# CHECK-NEXT: Exports: +# CHECK-NEXT: - Name: memory +# CHECK-NEXT: Kind: MEMORY +# CHECK-NEXT: Index: 0 +# CHECK-NEXT: - Name: _start +# CHECK-NEXT: Kind: FUNCTION +# CHECK-NEXT: Index: 0 +# CHECK-NEXT: - Name: foo_global +# CHECK-NEXT: Kind: GLOBAL +# CHECK-NEXT: Index: 1 +# CHECK-NEXT: - Type: CODE + +# CHECK-SP: - Type: EXPORT +# CHECK-SP-NEXT: Exports: +# CHECK-SP-NEXT: - Name: memory +# CHECK-SP-NEXT: Kind: MEMORY +# CHECK-SP-NEXT: Index: 0 +# CHECK-SP-NEXT: - Name: __stack_pointer +# CHECK-SP-NEXT: Kind: GLOBAL +# CHECK-SP-NEXT: Index: 0 +# CHECK-SP-NEXT: - Name: _start +# CHECK-SP-NEXT: Kind: FUNCTION +# CHECK-SP-NEXT: Index: 0 +# CHECK-SP-NEXT: - Type: CODE + +# CHECK-ALL: - Type: EXPORT +# CHECK-ALL-NEXT: Exports: +# CHECK-ALL-NEXT: - Name: memory +# CHECK-ALL-NEXT: Kind: MEMORY +# CHECK-ALL-NEXT: Index: 0 +# CHECK-ALL-NEXT: - Name: __wasm_call_ctors +# CHECK-ALL-NEXT: Kind: FUNCTION +# CHECK-ALL-NEXT: Index: 0 +# CHECK-ALL-NEXT: - Name: _start +# CHECK-ALL-NEXT: Kind: FUNCTION +# CHECK-ALL-NEXT: Index: 1 +# CHECK-ALL-NEXT: - Name: foo_global +# CHECK-ALL-NEXT: Kind: GLOBAL +# CHECK-ALL-NEXT: Index: 1 +# CHECK-ALL-NEXT: - Name: __dso_handle +# CHECK-ALL-NEXT: Kind: GLOBAL +# CHECK-ALL-NEXT: Index: 2 +# CHECK-ALL-NEXT: - Name: __data_end +# CHECK-ALL-NEXT: Kind: GLOBAL +# CHECK-ALL-NEXT: Index: 3 +# CHECK-ALL-NEXT: - Name: __global_base +# CHECK-ALL-NEXT: Kind: GLOBAL +# CHECK-ALL-NEXT: Index: 4 +# CHECK-ALL-NEXT: - Name: __heap_base +# CHECK-ALL-NEXT: Kind: GLOBAL +# CHECK-ALL-NEXT: Index: 5 +# CHECK-ALL-NEXT: - Name: __memory_base +# CHECK-ALL-NEXT: Kind: GLOBAL +# CHECK-ALL-NEXT: Index: 6 +# CHECK-ALL-NEXT: - Name: __table_base +# CHECK-ALL-NEXT: Kind: GLOBAL +# CHECK-ALL-NEXT: Index: 7 +# CHECK-ALL-NEXT: - Type: CODE diff --git a/lld/test/wasm/mutable-globals.s b/lld/test/wasm/mutable-globals.s --- a/lld/test/wasm/mutable-globals.s +++ b/lld/test/wasm/mutable-globals.s @@ -1,5 +1,6 @@ # RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s # RUN: not wasm-ld %t.o -o %t.wasm 2>&1 | FileCheck %s +# RUN: wasm-ld --features=mutable-globals %t.o -o %t.wasm .globl _start _start: diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp --- a/lld/wasm/Writer.cpp +++ b/lld/wasm/Writer.cpp @@ -453,7 +453,7 @@ if (!config->checkFeatures) return; - if (!config->relocatable && used.count("mutable-globals") == 0) { + if (!config->relocatable && allowed.count("mutable-globals") == 0) { for (const Symbol *sym : out.importSec->importedSymbols) { if (auto *global = dyn_cast(sym)) { if (global->getGlobalType()->Mutable) { @@ -571,12 +571,13 @@ } export_ = {name, WASM_EXTERNAL_FUNCTION, f->getFunctionIndex()}; } else if (auto *g = dyn_cast(sym)) { - // TODO(sbc): Remove this check once to mutable global proposal is - // implement in all major browsers. - // See: https://github.com/WebAssembly/mutable-global - if (g->getGlobalType()->Mutable) { - // Only __stack_pointer and __tls_base should ever be create as mutable. - assert(g == WasmSym::stackPointer || g == WasmSym::tlsBase); + if (g->getGlobalType()->Mutable && !g->getFile() && !g->forceExport) { + // Avoid exporting mutable globals are linker synthesized (e.g. + // __stack_pointer or __tls_base) unless they are explicitly exported + // from the command line. + // Without this check `--export-all` would cause any program using the + // stack pointer to export a mutable global even if non of the input + // files were built with the `mutable-globals` feature. continue; } export_ = {name, WASM_EXTERNAL_GLOBAL, g->getGlobalIndex()};