Changes

Revert "[DDG] Data Dependence Graph - DOT printer"

This reverts commit fd4a10732c8bd646ccc621c0a9af512be252f33a, to
investigate the failure on windows: http://lab.llvm.org:8011/#/builders/127/builds/3274

[libc++] Refactor allocate_shared to use an allocation guard

This commit is a step towards making it easier to add support for arrays
in allocate_shared. Adding support for arrays will require writing multiple
functions, and the current complexity of writing allocate_shared is
prohibitive for understanding.

Differential Revision: https://reviews.llvm.org/D93130

[AMDGPU] Use multi-dword flat scratch for spilling

Differential Revision: https://reviews.llvm.org/D93067

[mlir][OpDefGen] Add support for generating local functions for shared utilities

This revision adds a new `StaticVerifierFunctionEmitter` class that emits local static functions in the .cpp file for shared operation verification. This class deduplicates shared operation verification code by emitting static functions alongside the op definitions. These methods are local to the definition file, and are invoked within the operation verify methods. The first bit of shared verification is for the type constraints used when verifying operands and results. An example is shown below:

```
static LogicalResult localVerify(...) {
  ...
}

LogicalResult OpA::verify(...) {
  if (failed(localVerify(...)))
    return failure();
  ...
}

LogicalResult OpB::verify(...) {
  if (failed(localVerify(...)))
    return failure();
  ...
}
```

This allowed for saving >400kb of code size from a downstream TensorFlow project (~15% of MLIR code size).

Differential Revision: https://reviews.llvm.org/D91381

[LoopIdiomRecognize] Teach detectShiftUntilZeroIdiom to recognize loops where the counter is decrementing.

This adds support for loops like

unsigned clz(unsigned x) {
    unsigned w = sizeof (x) * CHAR_BIT;
    while (x) {
        w--;
        x >>= 1;
    }

    return w;
}

and

unsigned clz(unsigned x) {
    unsigned w = sizeof (x) * CHAR_BIT - 1;
    while (x >>= 1) {
        w--;
    }

    return w;
}

To support these we look for add x, -1 as well as add x, 1 that
we already matched. If the value was -1 we need to subtract from
the initial counter value instead of adding to it.

Fixes PR48404.

Differential Revision: https://reviews.llvm.org/D92745