[CIR] Vector constants #700
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Implement vector constants in ClangIR. Resolves issue llvm#498 - Add a `cir.const_vec`, simlar to `cir.const_array` and `cir.const_struct` Create a new kind of attribute, `cir::ConstVectorAttr` in the code or `#cir.const_vector` in the assembly, which represents a compile-time value of a `cir::VectorType`. The values for the elements within the vector are stored as attributes within an `mlir::ArrayAttr`. When doing CodeGen for a prvalue of vector type, try to represent it as `cir.const #cir.const_vector` first. If that fails, most likely because some of the elements are not compile-time values, fall back to the existing code that uses a `cir.vec.create` operation. When lowering directly to LLVM IR, lower `cir.const #cir.const_vector` as `llvm.mlir.constant(dense<[...]> : _type_) : _type_`. When lowering through other MLIR dialects, lower `cir.const #cir.const_vector` as `arith.constant dense<[...]> : _type_`. No new tests were added, but the expected results of the existing tests that use vector constants were updated.
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LGTM after few nits.
Another nice future addition would be to add a VecCreateOp::fold method, and whenever all elts are const, fold it to a mlir::cir::ConstVectorAttr. Then you could add VecCreateOp to the list in MergeCleanupsPass::runOnOperation(), to get that going.
(Alternatively, with this approach we wouldn't even need to change CIRGen to directly emit the attribute, but emitting it directly also makes sense)
Change the type of the elements field of `cir::ConstVectorAttr` from `mlir::Attribute` to `mlir::ArrayAttr`. The verifier already checked that it was an `ArrayAttr`. This change moves that checking to a lower level, into the CIR builder or parser.
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I resolved the code review requests, except for |
That can come next! Good to go after resolving conflicts. |
The change from member functions isa/cast/dyn_cast to the corresponding global functions had to be done manually in the code that was unique to branch feature/vec-const.
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I rebased my branch (with manual work to avoid the deprecated |
Implement vector constants in ClangIR.
Resolves issue #498 - Add a
cir.const_vec, simlar tocir.const_arrayandcir.const_structCreate a new kind of attribute,
cir::ConstVectorAttrin the code or#cir.const_vectorin the assembly, which represents a compile-time value of acir::VectorType. The values for the elements within the vector are stored as attributes within anmlir::ArrayAttr.When doing CodeGen for a prvalue of vector type, try to represent it as
cir.const #cir.const_vectorfirst. If that fails, most likely because some of the elements are not compile-time values, fall back to the existing code that uses acir.vec.createoperation.When lowering directly to LLVM IR, lower
cir.const #cir.const_vectorasllvm.mlir.constant(dense<[...]> : _type_) : _type_.When lowering through other MLIR dialects, lower
cir.const #cir.const_vectorasarith.constant dense<[...]> : _type_.No new tests were added, but the expected results of the existing tests that use vector constants were updated.