This restores D132311, which was reverted in
29c841ce93e087fa4e0c5f3abae94edd460bc24a (Sep 2022) due to certain files
not buildable with GCC 7.3.0. The previous attempt was reverted by
6cd9608fb37ca2418fb44b57ec955bb5efe10689 (Dec 2020).
This time, GCC 7.3.0 has existing build errors for a long time due to
structured bindings for many files, e.g.
```
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:9098:13: error: cannot decompose class type ‘std::pair<llvm::Value*, const llvm::SCEV*>’: both it and it
s base class ‘std::pair<llvm::Value*, const llvm::SCEV*>’ have non-static data members
for (auto [_, Stride] : Legal->getLAI()->getSymbolicStrides()) {
^~~~~~~~~~~
```
... and also some `error: duplicate initialization of` instances due to llvm/Transforms/IPO/Attributor.h.
---
GCC 7.5.0 has a bug that, without this change, certain `SmallVector` with a `std::pair` element type like `SmallVector<std::pair<Instruction * const, Info>, 0> X;` lead to spurious
```
/tmp/opt/gcc-7.5.0/include/c++/7.5.0/type_traits:878:48: error: constructor required before non-static data member for ‘...’ has been parsed
```
Switching to std::is_trivially_{copy/move}_constructible fixes the error.
This commit comprises a number of related changes:
(1) Reintroduces the semantic distinction between `parseVarUsage` vs `parseVarBinding`, adds documentation explaining the distinction, and adds commentary to the one place that violates the desired/intended semantics.
(2) Improves documentation/commentary about the forward-declaration of level-vars, and about the meaning of the `bool` parameter to `parseLvlSpec`.
(2) Removes the `VarEnv::addVars` method, and instead has `DimLvlMapParser` handle the conversion issues directly. In particular, the parser now stores and maintains the `{dims,lvls}AndSymbols` arrays, thereby avoiding the O(n^2) behavior of scanning through the entire `VarEnv` for each `parse{Dim,Lvl}Spec` call. Unfortunately there still remains another source of O(n^2) behavior, namely: the `AsmParser::parseAffineExpr` method will copy the `DimLvlMapParser::{dims,lvls}AndSymbols` arrays into `AffineParser::dimsAndSymbols` on each `parse{Dim,Lvl}Spec` call; but fixing that would require extensive changes to `AffineParser` itself.
Depends On D155532
Reviewed By: Peiming
Differential Revision: https://reviews.llvm.org/D155533
This change is mostly for brevity's sake; but it also paves the way for the `Policy` enum to be reuseable for other situations that require the same three-way semantics.
Reviewed By: Peiming
Differential Revision: https://reviews.llvm.org/D155532
Since `StringRef::empty` can be used in constexpr context, it seems reasonable that `SMLoc::isValid` should be too. The default-ctor and `operator==` are made constexpr for consistency.
In particular, the `constexpr` keyword is needed for silencing warnings on Windows (whereas Linux allows constexpr usage without the keyword).
Reviewed By: jpienaar
Differential Revision: https://reviews.llvm.org/D154741
(1) uses the previously introduce API to reuse AffineExpr parser without codedup
(2) solves the look-ahead problem when parsing level spec
Reviewed By: Peiming
Differential Revision: https://reviews.llvm.org/D154254
We are in the progress of migrating to a much improved surface syntax for the Sparse Tensor Encoding Attribute (STEA).
You can see a preview of this in the StableHLO RFC at
https://github.com/openxla/stablehlo/blob/main/rfcs/20230210-sparsity.md
//**This design is courtesy Wren Romano.**//
This initial revision
(1) Introduces the first version of a new parser written by Wren Romano
(2) Introduces a simple "migration plan" using NEW_SYNTAX on the STEA, which will allow us to test the new parser with new examples, as well as migrate existing examples over without the need to rewrite them all
This first "drop" merely provides the entry points to parse the new syntax. The parser is still under active development. For example, we need to address the "lookahead" issue when parsing the lvl spec (viz. do we see l0 = d0 or a direct d0). Another larger task is to actually implement "affine" parsing (since the MLIR affine parser is not accessible in other parts of the tree).
EXAMPLE:
Currently, CSR looks like
#CSR = #sparse_tensor.encoding<{
lvlTypes = ["dense","compressed"],
dimToLvl = affine_map<(i,j) -> (i,j)>
}>
but you can "force" the new parser with
#CSR = #sparse_tensor.encoding<{
NEW_SYNTAX =
(d0, d1) -> (l0 = d0 : dense, l1 = d1 : compressed)
}>
Reviewed By: Peiming
Differential Revision: https://reviews.llvm.org/D153997
