This function is used to constrain a register class to a sub-class that
supports the given sub-register index.
For example, getSubClassWithSubReg(GR32, sub_8bit) -> GR32_ABCD.
The function will be used to compute register classes when emitting
INSERT_SUBREG and EXTRACT_SUBREG nodes and for register class inflation
of sub-register operations.
The version provided by TableGen is usually adequate, but targets can
override.
llvm-svn: 141142
The set of register classes should be closed under sub-register
operations and intersections. That will allow the register allocator to
model combinations of constraints accurately.
This patch implements the easiest form of register class inference: For
every register class, and for every sub-register SubIdx, the subset of
registers in RC that have a SubIdx sub-register should also be a register
class.
This does create some new register classes for the targets in the tree:
ARM gets a new QQQQPR_with_ssub_0. This class was omitted from the .td
file on purpose because it only has two registers. InstrEmitter and
RegisterCoalescer have safeguards against selecting too small register
classes, so it is harmless.
PowerPC gets a G8RC_with_sub_32 class because LR is not a sub_32
sub-register of LR8. I think that might be an omission?
X86 puts RIP in the GR64 class, and since that register doesn't have
8-bit sub-registers, we get:
GR64_with_sub_8bit
GR64_TC_with_sub_8bit
GR64_NOREX_with_sub_8bit
GR64_TC_with_sub_8bit_hi
The various CodeGen classes have already been fixed so adding new
register classes should not affect compile time.
llvm-svn: 141084
When TableGen starts creating its own register classes, the synthesized
classes won't have a Record reference. All register classes must have a
name, though.
llvm-svn: 141081
This uses less memory and it reduces the complexity of sub-class
operations:
- hasSubClassEq() and friends become O(1) instead of O(N).
- getCommonSubClass() becomes O(N) instead of O(N^2).
In the future, TableGen will infer register classes. This makes it
cheap to add them.
llvm-svn: 140898
All register classes are given a lower ID than their sub-classes.
Cliques are ordered alphabetically.
This will be used to simplify some sub-class operations.
llvm-svn: 140826
Many targets use pseudo instructions to help register allocation. Like
the COPY instruction, these pseudos can be expanded after register
allocation. The early expansion can make life easier for PEI and the
post-ra scheduler.
This patch adds a hook that is called for all remaining pseudo
instructions from the ExpandPostRAPseudos pass.
llvm-svn: 140472
No functionality change. The hook makes it explicit which patterns
require "special" handling. i.e. it self-documents tblgen
deficiencies. I plan to add verification in ExpandISelPseudos and
Thumb2SizeReduce to catch any missing hasPostISelHooks. Otherwise it's
too fragile.
llvm-svn: 140160
Modified ARMISelLowering::AdjustInstrPostInstrSelection to handle the
full gamut of CPSR defs/uses including instructins whose "optional"
cc_out operand is not really optional. This allowed removal of the
hasPostISelHook to simplify the .td files and make the implementation
more robust.
Fixes rdar://10137436: sqlite3 miscompile
llvm-svn: 140134
The immediate offset of the non-writeback i8 form (encoding T4) allows
negative offsets only. The positive offset form of the encoding is the
LDRT instruction. Immediate offsets in the range [0,255] use encoding T3
instead.
llvm-svn: 139254
