forked from OSchip/llvm-project
a1ae9566ea
Summary: The WebAssembly backend automatically lowers atomic operations and TLS to nonatomic operations and non-TLS data when either are present and the atomics or bulk-memory features are not present, respectively. The resulting object is no longer thread-safe, so the linker has to be told not to allow it to be linked into a module with shared memory. This was previously done by disallowing the 'atomics' feature, which prevented any objct with its atomic operations or TLS removed from being linked with any object containing atomics or TLS, and therefore preventing it from being linked into a module with shared memory since shared memory requires atomics. However, as of https://github.com/WebAssembly/threads/issues/144, the validation rules are relaxed to allow atomic operations to validate with unshared memories, which makes it perfectly safe to link an object with stripped atomics and TLS with another object that still contains TLS and atomics as long as the resulting module has an unshared memory. To allow this kind of link, this patch disallows a pseudo-feature 'shared-mem' rather than 'atomics' to communicate to the linker that the object is not thread-safe. This means that the 'atomics' feature is available to accurately reflect whether or not an object has atomics enabled. As a drive-by tweak, this change also requires that bulk-memory be enabled in addition to atomics in order to use shared memory. This is because initializing shared memories requires bulk-memory operations. Reviewers: aheejin, sbc100 Subscribers: dschuff, jgravelle-google, hiraditya, sunfish, jfb, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D79542 |
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.. | ||
CMakeLists.txt | ||
Config.h | ||
Driver.cpp | ||
InputChunks.cpp | ||
InputChunks.h | ||
InputEvent.h | ||
InputFiles.cpp | ||
InputFiles.h | ||
InputGlobal.h | ||
LTO.cpp | ||
LTO.h | ||
MarkLive.cpp | ||
MarkLive.h | ||
Options.td | ||
OutputSections.cpp | ||
OutputSections.h | ||
OutputSegment.h | ||
Relocations.cpp | ||
Relocations.h | ||
SymbolTable.cpp | ||
SymbolTable.h | ||
Symbols.cpp | ||
Symbols.h | ||
SyntheticSections.cpp | ||
SyntheticSections.h | ||
Writer.cpp | ||
Writer.h | ||
WriterUtils.cpp | ||
WriterUtils.h |