[Mlir-commits] [mlir] [mlir] Add the concept of ASM dialect aliases (PR #86033)

[Fabian Mora]

fabianmcg wrote:

## Test
I used python to create a synthetic test:
```python
for i in range(0, 10000):
    print("func.func @func{0}(%A: memref<?xi32, {0}>, %i: index) {{".format(i))
    for j in range(0, 20):
        print("  %{0} = memref.load %A[%i] : memref<?xi32, {1}>".format(j, i))
        print("  memref.store %{0}, %A[%i] : memref<?xi32, {1}>".format(j, i))
    print("  return")
    print("}")
```
Which then I transformed to LLVM with:
```bash
mlir-opt test.mlir  --finalize-memref-to-llvm --convert-func-to-llvm --canonicalize -o llvm.mlir
```
To get something that looks like:
```mlir
    %0 = llvm.getelementptr %arg1[%arg5] : (!llvm.ptr, i64) -> !llvm.ptr, i32
    %1 = ptr.load %0 : !llvm.ptr -> i32
    %2 = llvm.getelementptr %arg1[%arg5] : (!llvm.ptr, i64) -> !llvm.ptr, i32
    ptr.store %1, %2 : i32, !llvm.ptr
```
and
```mlir
    %0 = llvm.getelementptr %arg1[%arg5] : (!llvm.ptr, i64) -> !llvm.ptr, i32
    %1 = llvm.load %0 : !llvm.ptr -> i32
    %2 = llvm.getelementptr %arg1[%arg5] : (!llvm.ptr, i64) -> !llvm.ptr, i32
    llvm.store %1, %2 : i32, !llvm.ptr
```
for a total of `830003` lines.
Then I tested parse and printing times with:
```bash
mlir-opt llvm.mlir --mlir-timing -o llvm-other.mlir
```
Before the change:
```
  Total Execution Time: 7.3231 seconds

  ----Wall Time----  ----Name----
    6.1180 ( 83.5%)  Parser
    1.0906 ( 14.9%)  Output
    0.1144 (  1.6%)  Rest
    7.3231 (100.0%)  Total
```
After the change:
```
  Total Execution Time: 5.3205 seconds

  ----Wall Time----  ----Name----
    3.0505 ( 57.3%)  Parser
    2.1249 ( 39.9%)  Output
    0.1451 (  2.7%)  Rest
    5.3205 (100.0%)  Total
```
## Results
Parsing takes less time after change, without a good reason as to why. But printing does take 8% more after the change.

## Side note
While I was moving flang tests to use Ptr, I realized that this method has another flaw. Aliases are not always computed, for example, when emitting errors it prints the full version of the type.


https://github.com/llvm/llvm-project/pull/86033