This fixes a crash in SCF→GPU when building the per‑dim index for mapped
scf.parallel.

**Change**:
- Map step/lb through cloningMap, then run ensureLaunchIndependent.
- If either is still unavailable at launch scope, emit a match‑failure;
otherwise build the affine.apply.

**Why this is correct:**
- Matches how the pass already handles launch bounds; avoids creating an
op with invalid operands and replaces a segfault with a clear
diagnostic.

**Tests**:
- Added two small regressions that lower to gpu.launch and exercise the
affine.apply path.

Fixes :  #167654

Signed-off-by: Shashi Shankar <shashishankar1687@gmail.com>

Use LocalAliasAnalysis to improve handling of side effects in nested
scf.parallel. If the written memory outside nested scf.parallel is not
alias to the memory accessed inside the nested loop, we can convert it
to gpu.launch.

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

See https://github.com/llvm/llvm-project/pull/147168 for more info.

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

ArrayRef has a constructor that accepts std::nullopt.  This
constructor dates back to the days when we still had llvm::Optional.

Since the use of std::nullopt outside the context of std::optional is
kind of abuse and not intuitive to new comers, I would like to move
away from the constructor and eventually remove it.

One of the uses of std::nullopt is in a the constructors for
TypeRange.  This patch takes care of the migration where we need
TypeRange() to facilitate perfect forwarding.  Note that {} would be
ambiguous for perfecting forwarding to work.

Support reductions in SCFToGPU: `scf.parallel` and `scf.reduce` op
combination is now converted to a `gpu.all_reduce` op.