forked from OSchip/llvm-project
6d37a255e2
This commit introduces a generic dialect conversion/lowering/legalization pass and illustrates it on StandardOps->LLVMIR conversion. It partially reuses the PatternRewriter infrastructure and adds the following functionality: - an actual pass; - non-default pattern constructors; - one-to-many rewrites; - rewriting terminators with successors; - not applying patterns iteratively (unlike the existing greedy rewrite driver); - ability to change function signature; - ability to change basic block argument types. The latter two things required, given the existing API, to create new functions in the same module. Eventually, this should converge with the rest of PatternRewriter. However, we may want to keep two pass versions: "heavy" with function/block argument conversion and "light" that only touches operations. This pass creates new functions within a module as a means to change function signature, then creates new blocks with converted argument types in the new function. Then, it traverses the CFG in DFS-preorder to make sure defs are converted before uses in the dominated blocks. The generic pass has a minimal interface with two hooks: one to fill in the set of patterns, and another one to convert types for functions and blocks. The patterns are defined as separate classes that can be table-generated in the future. The LLVM IR lowering pass partially inherits from the existing LLVM IR translator, in particular for type conversion. It defines a conversion pattern template, instantiated for different operations, and is a good candidate for tablegen. The lowering does not yet support loads and stores and is not connected to the translator as it would have broken the existing flows. Future patches will add missing support before switching the translator in a single patch. PiperOrigin-RevId: 230951202 |
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