* [codegen] add encodings for iadd carry variants
Add encodings for iadd carry variants (iadd_cout, iadd_cin, iadd_carry)
for x86_32, enabling the legalization for iadd.i64 to work.
* [codegen] remove support for iadd carry variants on riscv
Previously, the carry variants of iadd (iadd_cin, iadd_cout and
iadd_carry) were being legalized for isa/riscv since RISC architectures
lack a flags register.
This forced us to return and accept booleans for these operations, which
proved to be problematic and inconvenient, especially for x86.
This commit removes support for said statements and all dependent
statements for isa/riscv so that we can work on a better legalization
strategy in the future.
* [codegen] change operand type from bool to iflag for iadd carry variants
The type of the carry operands for the carry variants of the iadd
instruction (iadd_cin, iadd_cout, iadd_carry) was bool for compatibility
reasons for isa/riscv. Since support for these instructions on RISC
architectures has been temporarily suspended, we can safely change the
type to iflags.
-Add resumable_trap, safepoint, isnull, and null instructions
-Add Stackmap struct and StackmapSink trait
Co-authored-by: Mir Ahmed <mirahmed753@gmail.com>
Co-authored-by: Dan Gohman <sunfish@mozilla.com>
This makes non-legalized jump table instructions operate on operands with
pointer-sized types. This means we need to extend smaller types into the
pointer-sized operand, when the two don't match.
This follows the rest of the code base data structures, where we have a
mutable data structure builder; once the data structure is constructed,
it's immutable.
This also makes the definition of instructions easier, and it paves the
way for defining immediate variants.
This is also https://bugzilla.mozilla.org/show_bug.cgi?id=1552737.
Cranelift currently has a tendency to create redundant copies (self-copies) of
values from a stack slot back to the same stack slot. This generates a
pointless load and store and an unnecessary register use. The copies are
created by `visit_inst` in regalloc/reload.rs. They appear to occur mostly,
but not exclusively, at loop heads. It's unclear why this happens.
This patch adds a special case to `visit_inst` to find such copies. They are
converted into a new instruction, `copy_nop`, which takes and produces the
same SSA names, so as not to break any of the SSA invariants, but which has a
zero-length encoding, hence removing the copy at emission time.
`copy_nop`s source and destination operands must be stack slots and of course
the *same* stack slot. The verifier has been enhanced to check this, since
misuse of `copy_nop` will likely lead to hard-to-find incorrect-code bugs.
Attempts were made to write a standalone .clif test case. But these failed
because it appears the .clif parser accepts but ignores location hints that
are stack slots. So it's impossible to write, in clif, the exact form of
`copy` instruction that triggers the transformation.
