This reapplies 54a61c94f9, its follow up in 547b712500, which were
reverted 95fe61e639. Original commit message:
VarLoc based LiveDebugValues will abandon variable location propagation if
there are too many blocks and variable assignments in the function. If it
didn't, and we had (say) 1000 blocks and 1000 variables in scope, we'd end
up with 1 million DBG_VALUEs just at the start of blocks.
Instruction-referencing LiveDebugValues should honour this limitation too
(because the same limitation applies to it). Hoist the relevant command
line options into LiveDebugValues.cpp and pass it down into the
implementation classes as an argument to ExtendRanges. I've duplicated all
the run-lines in live-debug-values-cutoffs.mir to have an
instruction-referencing flavour.
Differential Revision: https://reviews.llvm.org/D107823
VarLoc based LiveDebugValues will abandon variable location propagation if
there are too many blocks and variable assignments in the function. If it
didn't, and we had (say) 1000 blocks and 1000 variables in scope, we'd end
up with 1 million DBG_VALUEs just at the start of blocks.
Instruction-referencing LiveDebugValues should honour this limitation too
(because the same limitation applies to it). Hoist the relevant command
line options into LiveDebugValues.cpp and pass it down into the
implementation classes as an argument to ExtendRanges. I've duplicated all
the run-lines in live-debug-values-cutoffs.mir to have an
instruction-referencing flavour.
Differential Revision: https://reviews.llvm.org/D107823
This patch imports the instruction-referencing implementation of
LiveDebugValues proposed here:
http://lists.llvm.org/pipermail/llvm-dev/2020-June/142368.html
The new implementation is unreachable in this patch, it's the next patch
that enables it behind a command line switch. Briefly, rather than
tracking variable locations by just their location as the 'VarLoc'
implementation does, this implementation does it by value:
* Each value defined in a function is numbered, and propagated through
dataflow,
* Each DBG_VALUE reads a machine value number from a machine location,
* Variable _values_ are propagated through dataflow,
* Variable values are translated back into locations, DBG_VALUEs
inserted to specify where those locations are.
The ultimate aim of this is to enable referring to variable values
throughout post-isel code, rather than locations. Those patches will
build on top of this new LiveDebugValues implementation in later patches
-- it can't be done with the VarLoc implementation as we don't have
value information, only locations.
Differential Revision: https://reviews.llvm.org/D83047
This patch renames the current LiveDebugValues class to "VarLocBasedLDV"
and removes the pass-registration code from it. It creates a separate
LiveDebugValues class that deals with pass registration and management,
that calls through to VarLocBasedLDV::ExtendRanges when
runOnMachineFunction is called. This is done through the "LDVImpl"
abstract class, so that a future patch can install the new
instruction-referencing LiveDebugValues implementation and have it
picked at runtime.
No functional change is intended, just shuffling responsibilities.
Differential Revision: https://reviews.llvm.org/D83046
Jeremy Morse