forked from OSchip/llvm-project
8e3e56f2a3
Summary: Although using `__builtin_shufflevector` and the `shufflevector` instruction works fine, they are not opaque to the optimizer. As a result, DAGCombine can potentially reduce the number of shuffles and change the shuffle masks. This is unexpected behavior for users of the WebAssembly SIMD intrinsics who have crafted their shuffles to optimize the code generated by engines. This patch solves the problem by adding a new shuffle intrinsic that is opaque to the optimizers in line with the decision of the WebAssembly SIMD contributors at https://github.com/WebAssembly/simd/issues/196#issuecomment-622494748. In the future we may implement custom DAG combines to properly optimize shuffles and replace this solution. Reviewers: aheejin, dschuff Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, cfe-commits, llvm-commits Tags: #clang, #llvm Differential Revision: https://reviews.llvm.org/D66983 |
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