[BOLT][AArch64] Add support for compact code model (#112110)

Add `--compact-code-model` option that executes alternative branch
relaxation with an assumption that the resulting binary has less than

[BOLT][AArch64] Add support for compact code model (#112110)

Add `--compact-code-model` option that executes alternative branch
relaxation with an assumption that the resulting binary has less than
128MB of code. The relaxation is done in `relaxLocalBranches()`, which
operates on a function level and executes on multiple functions in
parallel.

Running the new option on AArch64 Clang binary produces slightly smaller
code and the relaxation finishes in about 1/10th of the time.

Note that the new `.text` has to be smaller than 128MB, *and* `.plt` has
to be closer than 128MB to `.text`.

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[BOLT][NFC] Extend updateLayoutIndices (#93861)

Make FunctionLayout::updateLayoutIndices const and add an overloaded
function that updates LayoutIndices given an Order parameter.

[BOLT][NFC] Clean includes, add license headers (#87200)

[BOLT] CDSplit main logic part 1/2 (#73895)

This diff defines and initializes auxiliary variables used by CDSplit
and implements two important helper functions. The first helper function
approxima

[BOLT] CDSplit main logic part 1/2 (#73895)

This diff defines and initializes auxiliary variables used by CDSplit
and implements two important helper functions. The first helper function
approximates the block level size increase if a function is hot-warm
split at a given split index (X86 specific). The second helper function
finds all calls in the form of X->Y or Y->X for each BF given function
order [... X ... BF ... Y ...]. These calls are referred to as "cover
calls". Their distance will decrease if BF's hot fragment size is
further reduced by hot-warm splitting. NFC.

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[BOLT] Use range-based for loops (NFC)

LLVM Coding Standards discourage for_each unless callable objects
already exist.

[BOLT] Track fragment info for all split fragments

To generate all symbols correctly, it is necessary to record the address
of each fragment. This patch moves the address info for the main and
cold

[BOLT] Track fragment info for all split fragments

To generate all symbols correctly, it is necessary to record the address
of each fragment. This patch moves the address info for the main and
cold fragments from BinaryFunction to FunctionFragment, where this data
is recorded for all fragments.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D132051

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[BOLT] Allocate FunctionFragment on heap

This changes `FunctionFragment` from being used as a temporary proxy
object to access basic block ranges to a heap-allocated object that can
store fragment-s

[BOLT] Allocate FunctionFragment on heap

This changes `FunctionFragment` from being used as a temporary proxy
object to access basic block ranges to a heap-allocated object that can
store fragment-specific information.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D132050

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Revert "[BOLT] Allocate FunctionFragment on heap"

This reverts commit 101344af1af82d1633c773b718788eaa813d7f79.

Revert "[BOLT] Track fragment info for all split fragments"

This reverts commit 7e254818e49454a53bd00e3737007025b62d0f79.

[BOLT] Track fragment info for all split fragments

To generate all symbols correctly, it is necessary to record the address
of each fragment. This patch moves the address info for the main and
cold

[BOLT] Track fragment info for all split fragments

To generate all symbols correctly, it is necessary to record the address
of each fragment. This patch moves the address info for the main and
cold fragments from BinaryFunction to FunctionFragment, where this data
is recorded for all fragments.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D132051

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[BOLT] Allocate FunctionFragment on heap

This changes `FunctionFragment` from being used as a temporary proxy
object to access basic block ranges to a heap-allocated object that can
store fragment-s

[BOLT] Allocate FunctionFragment on heap

This changes `FunctionFragment` from being used as a temporary proxy
object to access basic block ranges to a heap-allocated object that can
store fragment-specific information.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D132050

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[BOLT] Generate sections for multiple fragments

This patch adds support to generate any number of sections that are
assigned to fragments of functions that are split more than two-way.
With this, a

[BOLT] Generate sections for multiple fragments

This patch adds support to generate any number of sections that are
assigned to fragments of functions that are split more than two-way.
With this, a function's *nth* split fragment goes into section
`.text.cold.n`.

This also changes `FunctionLayout::erase` to make sure, that there are
no empty fragments at the end of the function. This sometimes happens
when blocks are erased from the function. To avoid creating symbols
pointing to these fragments, they need to be removed.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D130521

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[BOLT] Remove old layout from function layout

To track whether a function's new layout is different from its old
layout when updating it, the old layout would be kept around in memory
indefinitely (

[BOLT] Remove old layout from function layout

To track whether a function's new layout is different from its old
layout when updating it, the old layout would be kept around in memory
indefinitely (if the new layout is different). This was used only for
debugging/logging purposes. This patch forces the caller of function
layout's update method to copy the old layout into a temporary if they
need it by removing the old layout fields.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D131413

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[BOLT] Add main fragment to function layout

Functions that do not contain any code still have to be emitted. This
occurs on AArch64 where functions can consist only of a constant island.
To support

[BOLT] Add main fragment to function layout

Functions that do not contain any code still have to be emitted. This
occurs on AArch64 where functions can consist only of a constant island.
To support fragment semantics in code emission, this commits adds a
guaranteed main fragment to function layout. This fragment might be
empty, but allows us omit checks whether the function is empty in most
places.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D130051

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Use llvm::erase_if (NFC)

[BOLT] Add function layout class

This patch adds a dedicated class to keep track of each function's
layout. It also lays the groundwork for splitting functions into
multiple fragments (as opposed to

[BOLT] Add function layout class

This patch adds a dedicated class to keep track of each function's
layout. It also lays the groundwork for splitting functions into
multiple fragments (as opposed to a strict hot/cold split).

Reviewed By: maksfb

Differential Revision: https://reviews.llvm.org/D129518

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