vscc

A lightweight, fast x86-64 compiler backend library.

• No third-party dependencies
• JIT compilation
• SYS-V ABI compliant

build (cmake)

git clone https://github.com/dmaivel/vscc.git
cd vscc
mkdir build
cd build
cmake ..
cmake --build . --config Release

To build one of the examples, uncomment the frontend lines from the cmake file.

examples

The primary example is pyvscc, which is an experimental python compiler. However, this repository contains additional, smaller examples. The examples directory contains the following subprojects:

• basic_ir: tests the intermediate language
• codecheck: tests the ir, optimization, symbol generation and code generation
• mm_test: test the memory manager (lists)
• strlen_jit: generate a strlen implementation at runtime

to-do

This project is currently unfinished with a vast majority of the feature set either needing to be finished, polished, rewritten, or awaiting implementation. This is a list of priorities for future development:

• Internal memory manager
• User memory manager (free code, symbols, ir, memory limits)
• Refactor codegen implementation
  • create a codegen interface structure, contains function pointers
  • base for adding support for new ABIs/architectures
• Save/load IR to and from storage
• Full Sys-V support
• Basic support for all IR opcodes in codegen
• Finish implementing all IR opcodes in codegen
• Add/finish 8-bit & 16-bit support
• Add floating point support
• Add more optimization routines

Lower priority features:

• Support IR as source instead of just binary
• MS-ABI support
• x86 (32-bit) support
• AVX2 support

features

intermediate language

opcodes

Opcode	Description	Destination Operand	Source Operand	Support
O_ADD	Addition	Register	Register/Immediate	⚠️
O_LOAD	Load value from memory into register	Register	Register/Immediate	⚠️
O_STORE	Store value into register	Register	Register/Immediate	✔️
O_SUB	Subtraction	Register	Register/Immediate	⚠️
O_MUL	Multiplication	Register	Register/Immediate	⚠️
O_DIV	Division	Register	Register/Immediate	⚠️
O_XOR	Exclusive Or	Register	Register/Immediate	⚠️
O_AND	And	Register	Register/Immediate	⚠️
O_OR	Or	Register	Register/Immediate	⚠️
O_SHL	Left Shift	Register	Register/Immediate	⚠️
O_SHR	Right Shift	Register	Register/Immediate	⚠️
O_CMP	Compare register to value	Register	Register/Immediate	⚠️
O_JMP	Jump	Immediate		✔️
O_JE	Jump if equal	Immediate		✔️
O_JNE	Jump if not equal	Immediate		✔️
O_JBE	Jump if below/equal	Immediate		✔️
O_JA	Jump if above	Immediate		✔️
O_JS	Jump if sign	Immediate		✔️
O_JNS	Jump if not sign	Immediate		✔️
O_JP	Jump if parity	Immediate		✔️
O_JNP	Jump if not parity	Immediate		✔️
O_JL	Jump if less	Immediate		✔️
O_JGE	Jump if greater/equal	Immediate		✔️
O_JLE	Jump if less/equal	Immediate		✔️
O_JG	Jump if greater	Immediate		✔️
O_RET	Return	Register/Immediate		✔️
O_DECLABEL	Declare a label within a function for jumps	Immediate		✔️
O_PSHARG	Push an argument	Register/Immediate		⚠️
O_SYSCALL	Perform syscall (use vscc_pushs)			✔️
O_SYSCALL_PSHARG	Push an argument for syscall (don't use unless not using vscc_pushs)	Register/Immediate		⚠️
O_CALL	Call a function	Register (return value storage)	Immediate (pointer to function)	✔️
O_CALLADDR	Call a function (not IR) by its address	Register (return value storage)	Immediate (pointer to function)	✔️
O_LEA	Load effective address of register	Register	Register/Immediate	⚠️

❌ no support ⚠️ partial support ✔️ full support

planned

Opcode	Description	Destination Operand	Source Operand
O_FSTORE	Store floating point value into register	Register	Register/Immediate
O_FLOAD	Load floating point value from memory into register	Register	Register/Immediate
O_FADD	Addition	Register	Register/Immediate
O_FSUB	Subtraction	Register	Register/Immediate
O_FMUL	Multiplication	Register	Register/Immediate
O_FDIV	Division	Register	Register/Immediate

context initialization

struct vscc_context ctx = { 0 };

function initialization

struct vscc_function *function = vscc_init_function(&ctx, "function_name", SIZEOF_I32); // NO_RETURN, SIZEOF_I8, SIZEOF_I16, SIZEOF_I32, SIZEOF_I64, SIZEOF_PTR

register allocation

struct vscc_register *variable = vscc_alloc(function, "variable_name", SIZEOF_I32, NOT_PARAMETER, NOT_VOLATILE); // [NOT_PARAMETER/IS_PARAMETER], [NOT_VOLATILE/IS_VOLATILE]

global register allocation

struct vscc_register *global_variable = vscc_alloc_global(&ctx, "my_global_name", SIZEOF_I32, NOT_VOLATILE);

push instructions

/* standard push instructions */ 
vscc_push0(function, O_..., reg, imm);
vscc_push1(function, O_..., reg, reg);
vscc_push2(function, O_..., imm);
vscc_push3(function, O_..., reg);

/* syscall */
vscc_pushs(function, &syscall_desc);

/* call */
vscc_push0(function, O_CALL, variable_return_storage, (uintptr_t)callee_function);
_vscc_call(function, callee_function, variable_return_storage); // alternative to above

syscall descriptor example (write(...))

struct vscc_syscall_args syscall_write = {
    .syscall_id = 1,
    .count = 3,

    .values = { 1, (uintptr_t)string, (size_t)len },
    .type = { M_IMM, M_REG, M_REG }
};

saving/loading context

bool status;

status = vscc_ir_save(&ctx, "/path/to/save.vscc");
status = vscc_ir_load(&ctx, "/path/to/save.vscc");

code generation

context initialization

struct vscc_codegen_data compiled = { 0 }; 
struct vscc_codegen_interface interface = { 0 };

enable alignment

compiled.align = true; /* compiled is of type 'struct vscc_codegen_data' */

compile context

vscc_codegen_implement_x64(&interface, ABI_SYSV);
vscc_codegen(&ctx, &interface, &compiled, true); // true: generate symbols

optimization

optimizing routines must be called before codegen

eliminate dead store

vscc_optfn_elim_dead_store(function);