createCast in MergeFunctions did not consider ArrayTypes, which results
in the creation of a bitcast between ArrayTypes in the thunk function,
leading to an assertion failure in the provided test case.
The version of createCast in GlobalMergeFunctions does handle
ArrayTypes, so this common code has been factored out into the
IRBuilder.
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.
