Change of approach, it looks like it's a much better idea to deal with
the vregs that have LLTs and reg classes both properly, than trying to
avoid creating those across all GlobalISel passes and all targets.
The change mostly touches MachineRegisterInfo::constrainRegClass,
which is apparently only used by MachineCSE. The changes are NFC for
any pipeline but one that contains MachineCSE mid-GlobalISel.
NOTE on isCallerPreservedOrConstPhysReg change in MachineCSE:
There is no test covering it as the only way to insert a new pass
(MachineCSE) from a command line I know of is llc's -run-pass option,
which only works with MIR, but MIRParser freezes reserved registers upon
MachineFunctions creation, making it impossible to reproduce the state
that exposes the issue.
Reviwed By: aditya_nandakumar
Differential Revision: https://reviews.llvm.org/D53144
llvm-svn: 344822
Apparently, MachineInstr class definition as well as pretty much all of
the machine passes assume that the only kind of MachineInstr's operands
that is variadic for variadic opcodes is explicit non-definitions.
In particular, this assumption is made by MachineInstr::defs(), uses(),
and explicit_uses() methods, as well as by MachineCSE pass.
The assumption is incorrect judging from at least TableGen backend
implementation, that recognizes variable_ops in OutOperandList, and the
very existence of G_UNMERGE_VALUES generic opcode, or ARM load multiple
instructions, all of which have variadic defs.
In particular, MachineCSE pass breaks MIR with CSE'able G_UNMERGE_VALUES
instructions in it.
This commit implements MachineInstr::getNumExplicitDefs() similar to
pre-existing MachineInstr::getNumExplicitOperands(), fixes
MachineInstr::defs(), uses(), and explicit_uses(), and fixes MachineCSE
pass.
As the issue addressed seems to affect only machine passes that could be
ran mid-GlobalISel pipeline at the moment, the other passes aren't fixed
by this commit, like MachineLICM: that could be done on per-pass basis
when (if ever) they get adopted for GlobalISel.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D45640
llvm-svn: 334520
As Roman Tereshin pointed out in https://reviews.llvm.org/D45541, the
-global-isel option is redundant when -run-pass is given. -global-isel sets up
the GlobalISel passes in the pass manager but -run-pass skips that entirely and
configures it's own pipeline.
llvm-svn: 331603
Discussed here:
http://lists.llvm.org/pipermail/llvm-dev/2018-January/120320.html
In preparation for adding support for named vregs we are changing the sigil for
physical registers in MIR to '$' from '%'. This will prevent name clashes of
named physical register with named vregs.
llvm-svn: 323922
Right now, it is not possible to run MachineCSE in the middle of the
GlobalISel pipeline. Being able to run generic optimizations between the
core passes of GlobalISel was one of the goals of the new ISel framework.
This is the first attempt to do it.
The problem is that MachineCSE pass assumes all register operands have a
register class, which, in GlobalISel context, won't be true until after the
InstructionSelect pass. The reason for this behaviour is that before
replacing one virtual register with another, MachineCSE pass (and most of
the other optimization machine passes) must check if the virtual registers'
constraints have a (sufficiently large) intersection, and constrain the
resulting register appropriately if such intersection exists.
GlobalISel extends the representation of such constraints from just a
register class to a triple (low-level type, register bank, register
class).
This commit adds MachineRegisterInfo::constrainRegAttrs method that extends
MachineRegisterInfo::constrainRegClass to such a triple.
The idea is that going forward we should use:
- RegisterBankInfo::constrainGenericRegister within GlobalISel's
InstructionSelect pass
- MachineRegisterInfo::constrainRegClass within SelectionDAG ISel
- MachineRegisterInfo::constrainRegAttrs everywhere else regardless
the target and instruction selector it uses.
Patch by Roman Tereshin. Thanks!
llvm-svn: 322805
Roman Tereshin