EmitC currently models C's `&` and `*` operators via its `apply` op,
which has several drawbacks:
- Its pre-lvalue semantics combines dereferencing with memory access.
- Representing multiple opcodes (selected by an attribute) in a single
op complicates the code by adding a second, attribute-based selection
layer on top of MLIR's standard `isa<>` mechanism.
This patch adds two distinct, lvalue-based ops to model these C operators.
EmitC passes were converted to use the new ops instead of `apply`, which
is now deprecated.
Use wrappers around `std::accumulate` to make the code more concise and
less bug-prone: https://github.com/llvm/llvm-project/pull/162129.
With `std::accumulate`, it's the initial value that determines the
accumulator type. `llvm::sum_of` and `llvm::product_of` pick the right
accumulator type based on the range element type.
Found some funny bugs like a local accumulate helper that calculated a
sum with initial value of 1 -- we didn't hit the bug because the code
was actually dead...
This commit marks the type converter in `populate...` functions as
`const`. This is useful for debugging.
Patterns already take a `const` type converter. However, some
`populate...` functions do not only add new patterns, but also add
additional type conversion rules. That makes it difficult to find the
place where a type conversion was added in the code base. With this
change, all `populate...` functions that only populate pattern now have
a `const` type converter. Programmers can then conclude from the
function signature that these functions do not register any new type
conversion rules.
Also some minor cleanups around the 1:N dialect conversion
infrastructure, which did not always pass the type converter as a
`const` object internally.
This adds an `emitc.lvalue` type which models assignable lvlaues in the
type system. Operations modifying memory are restricted to this type
accordingly.
See also the discussion on
[discourse](https://discourse.llvm.org/t/rfc-separate-variables-from-ssa-values-in-emitc/75224/9).
The most notable changes are as follows.
- `emitc.variable` and `emitc.global` ops are restricted to return
`emitc.array` or `emitc.lvalue` types
- Taking the address of a value is restricted to operands with lvalue
type
- Conversion from lvalues into SSA values is done with the new
`emitc.load` op
- The var operand of the `emitc.assign` op is restricted to lvalue type
- The result of the `emitc.subscript` and `emitc.get_global` ops is a
lvalue type
- The operands and results of the `emitc.member` and
`emitc.member_of_ptr` ops are restricted to lvalue types
---------
Co-authored-by: Matthias Gehre <matthias.gehre@amd.com>
This adds
- `emitc.global` and `emitc.get_global` ops to model global variables
similar to how `memref.global` and `memref.get_global` work.
- translation of those ops to C++
- lowering of `memref.global` and `memref.get_global` into those ops
---------
Co-authored-by: Simon Camphausen <simon.camphausen@iml.fraunhofer.de>
