Crate rucc_target

Expand description

Target descriptions: triples, and the facts about a target that the rest of the compiler reads rather than hard-codes.

Design: spec/12-abi-and-runtime.md. Layer rank 2, see spec/18-package-layout.md.

The rule from spec/18-package-layout.md section 18.2 is that there is no target-specific code outside this crate, rucc-tuple, rucc-abi, rucc-sysroot and the per-target rule sets. Those four are one group rather than four exceptions: the tuple names a machine, rucc-abi says what its types look like and how its calls are made, rucc-sysroot says where its headers and libraries are, and this crate is what the rest of the compiler reads all of it through. Everything a pass needs to know about a target is a field it can read here. That rule is what makes the claim in spec/10-backend.md testable, namely that a new target is a rule set and a few data files, and M10 brings up a fourth target specifically to put a number on it.

TargetInfo::call is the other half of that rule and the one with teeth. How a structure travels between a caller and a callee is the target’s answer rather than C’s, so the walk to the IR flattens a C type into a Shape and asks here what form it takes. Every psABI rule is behind Call and nothing outside this crate matches on an architecture to find one. The rules themselves are rucc-abi’s, as data rather than as code, and this crate hands the question over to them. It answers None on a target whose ABI is not written down yet, which today is AArch64 on Windows and nothing else.

§Status

Triple parsing and the basic data model are real, which is what rucc --print-config reports, and so is the argument classification of every psABI in spec/12-abi-and-runtime.md sections 12.2 to 12.5, which rucc-abi describes as data and this crate selects between. x86-64’s register file is written down, in x86_64, along with what each of the two conventions over it does with each register, what each of its machine instructions does with its operands, and which instructions a frame is made of, which is FrameInsts. AArch64’s and RISC-V’s arrive with their backends. Machine models land in M6.

This crate is tier 3 in spec/18-package-layout.md section 18.5: its Rust API is explicitly unstable and will change without a major version bump.

Modules§

x86_64: The x86-64 register file, and where each of the two conventions over it puts things.

Structs§

AbiDescription: One psABI, completely.
BitInsts: What a pass has to know about a machine to work out which bits of a register anything reads.
BranchInsts: Every instruction a laid out branch is made of.
Call: The registers one call has left.
CallRegs: Which registers a calling convention gives which job.
Chkstk: What a platform calls the routine that reaches the pages of a frame before the frame is taken.
ClassInfo: One class of registers, and the registers in it.
ClassMoves: How a register of one class is moved between two registers and between a register and the frame.
Compare: One comparison, and what is left of it when the machine has already made it.
Copied: One address computation, and the move that says the same thing when the address is a register.
FlagInsts: What a pass has to know about a machine to find a comparison the machine has already made.
FrameInsts: Every instruction a prologue, an epilogue, a spill or a reload is made of.
Fusion: A comparison, and the two instructions a branch on its answer becomes.
Guard: Where a target keeps the word a stack protector’s canary is a copy of.
MachineInsts: What a pass has to know about a machine to tell an instruction it has from one it does not.
Narrowed: One instruction that writes a constant, and the narrower one that writes the same register.
OperandDesc: One operand of one instruction, as a target’s description of that instruction writes it.
ParseTripleError: Why a triple failed to parse.
PhysReg: One physical register, as its number inside its class.
Piece: One scalar inside an aggregate, at the offset the layout gave it.
Places: Where the values a call passes are, worked out one after another.
Probe: How a prologue touches the stack as it takes a frame, on a target that can.
Reader: One instruction that reads the condition state, and which part of it it reads.
RegClass: Which class a register or an operand belongs to.
RegFile: Every register a target has.
Scalar: One scalar, with the three facts a psABI reads about it.
Shape: An aggregate, as much of it as an ABI cares about.
ShortInsts: The shorter spellings this target has.
Stepped: One addition of a constant, and the shorter instruction that adds that constant and no other.
TargetInfo: The facts about a target that the compiler reads instead of hard-coding.
Tested: One comparison against a constant, and the shorter instruction that asks it against zero.
Timing: What one instruction costs.
TimingInsts: What a scheduler has to know about a machine to put a block in an order.
Trace: What a profiler’s hook at the top of every function is called on this platform.
Triple: A target triple.
Zeroed: One instruction that writes a constant, and the instruction that writes zero in fewer bytes.
Zeroing: One instruction that leaves behind the comparison of what it wrote against zero.

Enums§

Arch: A target architecture.
Arg: One argument, or one return value, as much of it as an ABI cares about.
BitFieldStyle: How a target allocates bit-fields into storage.
Constraint: Where an operand is allowed to live.
Env: The C runtime and ABI variant.
Kind: What a scalar is, once the ABI is the one asking.
ObjectFormat: The object file format to emit.
Os: The operating system a target runs on.
Pass: How one value travels.
Reads: Which part of what a comparison against zero left a condition is about.
Role: What an instruction does with an operand.
Segment: The storage an address is counted from, on a machine that has more than one.
Slot: One register’s worth of an aggregate that travels in registers, and which of the object’s bytes go in it.
Unit: The parts of a machine a scheduler counts.
VaList: The type a target’s __builtin_va_list is.
Where: Where one of the values a call passes is.