[all-commits] [llvm/llvm-project] 01a31c: [MLIR] EmitC: Add subscript operator (#84783)

[Matthias Gehre via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 01a31cee561efe90fbd1d33fa89f403dd8ff9012
      https://github.com/llvm/llvm-project/commit/01a31cee561efe90fbd1d33fa89f403dd8ff9012
  Author: Matthias Gehre <matthias.gehre at amd.com>
  Date:   2024-03-15 (Fri, 15 Mar 2024)

  Changed paths:
    M mlir/include/mlir/Dialect/EmitC/IR/EmitC.td
    M mlir/lib/Dialect/EmitC/IR/EmitC.cpp
    M mlir/lib/Target/Cpp/TranslateToCpp.cpp
    M mlir/test/Dialect/EmitC/invalid_ops.mlir
    A mlir/test/Target/Cpp/subscript.mlir

  Log Message:
  -----------
  [MLIR] EmitC: Add subscript operator (#84783)

Introduces a SubscriptOp that allows to write IR like
```
func.func @load_store(%arg0: !emitc.array<4x8xf32>, %arg1: !emitc.array<3x5xf32>, %arg2: index, %arg3: index) {
  %0 = emitc.subscript %arg0[%arg2, %arg3] : <4x8xf32>, index, index
  %1 = emitc.subscript %arg1[%arg2, %arg3] : <3x5xf32>, index, index
  emitc.assign %0 : f32 to %1 : f32
  return
}
```
which gets translated into the C++ code
```
v1[v2][v3] = v0[v1][v2];
```

To make this happen, this
- adds the SubscriptOp
- allows the subscript op as rhs of emitc.assign
- updates the emitter to print SubscriptOps

The emitter prints emitc.subscript in a delayed fashing to allow it
being used as lvalue.
I.e. while processing
```
%0 = emitc.subscript %arg0[%arg2, %arg3] : <4x8xf32>, index, index
```
it will not emit any text, but record in the `valueMapper` that the name
for `%0` is `v0[v1][v2]`, see `CppEmitter::getSubscriptName`. Only when
that result is then used (here in `emitc.assign`), that name is inserted
into the text.



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