Minimal IR Test

MiniIR is intended to provide a minimalist textual machine level intermediate representation to be used as an interchange format between compiler back-ends and experimental tools.

The current experimental tool is a prototype for register coalescing with aliasing constraints in the context of decoupled register allocation approach: First the register pressure is lowered (using puzzle solver to measure the register pressure), then the program is dump in MiniIR. Optionally the assignment given by the compiler back-end is also dump.

MiniIR is based on Yaml serialization format: http://en.wikipedia.org/wiki/YAML. A hash table is represented as {key1: value1, key2: value2, ...}. An array is represented as [ value1, value2, ... ]. The elements of arrays/hashs can also be listed in a one element per line way using "-" for arrays.

In this format:

• a register class (see examples/arm-registers.min) can be either a list of registers (eg registers: [S0, S1, S2,...]) or a union of some other register classes (eg classes: [ R, S, D, Q ]). The aliasing is represented using a mapping (eg D0: [S0, S1] says that D0 contains S0 and S1).
• a function (see examples/arm-diagonal-interpolation.min) has a list of basic blocks. Each basic block having a label used in jump (eg{ op: bgt, fallthru: exit, target: line_loop, uses: [ FR ] }) or in phi functions (eg { defs: [in2.R], op: phi, uses: [ in1.R<interpolate>, in3.R<line_loop> ] })
• for each variable the register class in which it can be allocated is provided in the hash table vars (eg. vars: { out: p32, outw: i32, in: p32 ... })
• an instruction has a list of definited variables (defs), a list of used variables.
• an operand v.Q means that variable v have to be on register class Q on this operand. Q can be a register (eg out.R0)
• an instruction has also a list of implicit definitions (implicit_defs) that appear semanticaly before the definition point in the instruction. This is useful for example to represent scratch registers eg(see http://trac-hg.assembla.com/minir-dev/browser/tests/test3.min ) as follow implicit_defs: [v3.R1<dead>].

There are still a few Todos.