For global function merging, the target of the arc-attached call must be
a constant and cannot be parameterized.
This change adds a check to bypass this case in `canParameterizeCallOperand()`.
This update follows up on change #112671 and is mostly a NFC, with the following exceptions:
- Introduced `-global-merging-skip-no-params` to bypass merging when no parameters are required.
- Parameter count is now calculated based on the unique hash count.
- Added `-global-merging-inst-overhead` to adjust the instruction overhead, reflecting the machine instruction size.
- Costs and benefits are now computed using the double data type. Since the finalization process occurs offline, this should not significantly impact build time.
- Moved a sorting operation outside of the loop.
This is a patch for
https://discourse.llvm.org/t/rfc-global-function-merging/82608.
This update follows up on change #112671 and is mostly a NFC, with the following exceptions:
- Introduced `-global-merging-skip-no-params` to bypass merging when no parameters are required.
- Parameter count is now calculated based on the unique hash count.
- Added `-global-merging-inst-overhead` to adjust the instruction overhead, reflecting the machine instruction size.
- Costs and benefits are now computed using the double data type. Since the finalization process occurs offline, this should not significantly impact build time.
- Moved a sorting operation outside of the loop.
This is a patch for
https://discourse.llvm.org/t/rfc-global-function-merging/82608.
This is a follow-up PR to refactor the initial global merge function
pass implemented in #112671.
It first collects stable functions relevant to the current module and
iterates over those only, instead of iterating through all stable
functions in the stable function map.
This is a patch for
https://discourse.llvm.org/t/rfc-global-function-merging/82608.
This is a follow-up PR to refactor the initial global merge function
pass implemented in #112671.
It first collects stable functions relevant to the current module and
iterates over those only, instead of iterating through all stable
functions in the stable function map.
This is a patch for
https://discourse.llvm.org/t/rfc-global-function-merging/82608.
This implements a global function merging pass. Unlike traditional
function merging passes that use IR comparators, this pass employs a
structurally stable hash to identify similar functions while ignoring
certain constant operands. These ignored constants are tracked and
encoded into a stable function summary. When merging, instead of
explicitly folding similar functions and their call sites, we form a
merging instance by supplying different parameters via thunks. The
actual size reduction occurs when identically created merging instances
are folded by the linker.
Currently, this pass is wired to a pre-codegen pass, enabled by the
`-enable-global-merge-func` flag.
In a local merging mode, the analysis and merging steps occur
sequentially within a module:
- `analyze`: Collects stable function hashes and tracks locations of
ignored constant operands.
- `finalize`: Identifies merge candidates with matching hashes and
computes the set of parameters that point to different constants.
- `merge`: Uses the stable function map to optimistically create a
merged function.
We can enable a global merging mode similar to the global function
outliner
(https://discourse.llvm.org/t/rfc-enhanced-machine-outliner-part-2-thinlto-nolto/78753/),
which will perform the above steps separately.
- `-codegen-data-generate`: During the first round of code generation,
we analyze local merging instances and publish their summaries.
- Offline using `llvm-cgdata` or at link-time, we can finalize all these
merging summaries that are combined to determine parameters.
- `-codegen-data-use`: During the second round of code generation, we
optimistically create merging instances within each module, and finally,
the linker folds identically created merging instances.
Depends on #112664
This is a patch for
https://discourse.llvm.org/t/rfc-global-function-merging/82608.
