We're generally not able to simplify signed pointer comparisons
(because we don't have no-wrap flags that would permit it), so
we shouldn't pretend that we can in the cost model.

The unsigned comparison case is also not modelled correctly,
as explained in the added comment. As this is a cost model
inaccuracy at worst, I'm leaving it alone for now.

Use ConstantFoldLoadFromConst() instead of a partial re-implementation.
This makes the code slightly more generic by not depending on the
exact structure of the constant.

Fix a bug I introduced in 721fdf1c9a73269280a504cbba847f4979512b66.

This is faster than checking for a SCEVConstant getMinusSCEV()
result. The results should be the same for non-degenerate cases.

This is a helper to avoid writing `getModule()->getDataLayout()`. I
regularly try to use this method only to remember it doesn't exist...

`getModule()->getDataLayout()` is also a common (the most common?)
reason why code has to include the Module.h header.

Clang-format InstructionSimplify and convert all "FunctionName"s to
"functionName".  This patch does touch a lot of files but gets done with
the cleanup of InstructionSimplify in one commit.

This is the alternative to the less invasive clang-format only patch: D126783

Reviewed By: spatel, rengolin

Differential Revision: https://reviews.llvm.org/D126889

Number of lines output by preprocessor:
before: 1065940348
after:  1065307662

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D120659

The current full unroll cost model does a symbolic evaluation of the loop up to a fixed limit. That symbolic evaluation currently simplifies to constants, but we can generalize to arbitrary Values using the InstructionSimplify infrastructure at very low cost.

By itself, this enables some simplifications, but it's mainly useful when combined with the branch simplification over in D102928.

Differential Revision: https://reviews.llvm.org/D102934