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//! x86-64 code generation for Shift-Or JIT.
use dynasmrt::{dynasm, DynasmApi, DynasmLabelApi};
use super::super::ShiftOr;
use super::jit::JitShiftOr;
/// Compiler for Shift-Or JIT on x86-64.
pub(super) struct ShiftOrJitCompiler;
impl ShiftOrJitCompiler {
/// Compiles a ShiftOr matcher to native code.
pub(super) fn compile(shift_or: &ShiftOr) -> Option<JitShiftOr> {
// Copy masks to heap FIRST (needs stable address for embedded pointer)
let mut masks = Box::new([0u64; 256]);
for (i, m) in shift_or.masks.iter().enumerate() {
masks[i] = *m;
}
// Copy follow sets to heap FIRST (needs stable address for embedded pointer)
let mut follow = Box::new([0u64; 64]);
for (i, f) in shift_or.follow.iter().enumerate() {
if i < 64 {
follow[i] = *f;
}
}
// Get stable pointers to embed in JIT code
let masks_ptr = masks.as_ptr() as u64;
let follow_ptr = follow.as_ptr() as u64;
let mut ops = dynasmrt::x64::Assembler::new().ok()?;
let find_offset = Self::emit_find(&mut ops, shift_or, masks_ptr, follow_ptr);
let code = ops.finalize().ok()?;
Some(JitShiftOr::new(
code,
find_offset,
masks,
follow,
shift_or.accept,
shift_or.first,
shift_or.position_count,
shift_or.nullable,
shift_or.has_leading_word_boundary,
shift_or.has_trailing_word_boundary,
shift_or.has_start_anchor,
shift_or.has_end_anchor,
))
}
fn emit_find(
ops: &mut dynasmrt::x64::Assembler,
shift_or: &ShiftOr,
masks_ptr: u64,
follow_ptr: u64,
) -> dynasmrt::AssemblyOffset {
// OPTIMIZED Function signature: fn(input: *const u8, len: usize, accept: u64, first: u64) -> i64
// Returns: packed (start << 32 | end) on match, or -1 if no match
//
// Masks and follow pointers are EMBEDDED in the JIT code (movabs instructions)
// This saves 2 parameter slots and 2 register moves in prologue.
//
// Register allocation:
// Unix (System V AMD64): rdi=input, rsi=len, rdx=accept, rcx=first
// Windows (Microsoft x64): rcx=input, rdx=len, r8=accept, r9=first
//
// Working registers:
// r10 = current start position being tried
// r11 = state (inverted: 0 = active position)
// r12 = follow pointer (embedded, kept in register for fast inner loop)
// r13 = accept mask (kept in register - checked every iteration)
// r14 = saved input pointer
// r15 = saved len
// rbx = masks pointer (embedded)
// [rsp+0] = first mask (only used at start of each position)
// [rsp+8] = last_match_start
// [rsp+16] = last_match_end
let offset = ops.offset();
let _ = shift_or.position_count;
// Platform-specific prologue
#[cfg(target_os = "windows")]
dynasm!(ops
; .arch x64
// Prologue - save callee-saved registers (including RDI/RSI on Windows)
; push rdi
; push rsi
; push rbx
; push r12
; push r13
; push r14
; push r15
; sub rsp, 24 // Allocate stack space for saved values
// Windows x64: rcx=input, rdx=len, r8=accept, r9=first
; mov r14, rcx // r14 = input
; mov r15, rdx // r15 = len
; mov rbx, QWORD masks_ptr as i64 // rbx = masks (EMBEDDED!)
; mov r12, QWORD follow_ptr as i64 // r12 = follow (EMBEDDED!)
; mov r13, r8 // r13 = accept
; mov [rsp], r9 // [rsp] = first
);
#[cfg(not(target_os = "windows"))]
dynasm!(ops
; .arch x64
// Prologue - save callee-saved registers
; push rbx
; push r12
; push r13
; push r14
; push r15
; sub rsp, 24 // Allocate stack space for saved values
// Unix: rdi=input, rsi=len, rdx=accept, rcx=first
; mov r14, rdi // r14 = input
; mov r15, rsi // r15 = len
; mov rbx, QWORD masks_ptr as i64 // rbx = masks (EMBEDDED!)
; mov r12, QWORD follow_ptr as i64 // r12 = follow (EMBEDDED!)
; mov r13, rdx // r13 = accept (was r8, now rdx)
; mov [rsp], rcx // [rsp] = first (was r9, now rcx)
);
dynasm!(ops
; .arch x64
// Initialize - match state on stack (less frequently accessed)
; xor r10d, r10d // r10 = start position = 0
; mov QWORD [rsp+16], -1 // last_match_end = -1
; mov QWORD [rsp+8], 0 // last_match_start = 0
// Outer loop: try each start position
; ->start_loop:
; cmp r10, r15
; jae ->done
// Initialize state for this start position
// state = !first | mask[input[start]]
; mov r11, [rsp] // r11 = first
; not r11 // r11 = !first
; movzx eax, BYTE [r14 + r10] // byte = input[start]
; or r11, [rbx + rax*8] // state |= mask[byte]
// Check immediate match at first byte
; mov rax, r11
; or rax, r13 // rax = state | accept (accept now in register!)
; cmp rax, -1
; jne ->found_at_start
// Inner loop: process remaining bytes
; lea rcx, [r10 + 1] // rcx = pos = start + 1
; ->inner_loop:
; cmp rcx, r15
; jae ->inner_done
// ============================================================
// Glushkov follow set computation:
// reachable = union of follow[i] for all active positions i
// state = !reachable | mask[byte]
//
// Active positions have bit=0 in state (inverted logic)
// So active = !state gives us 1 for active positions
// ============================================================
; mov rax, r11 // rax = state
; not rax // rax = active positions (1 = active)
; xor rdi, rdi // rdi = reachable = 0
// Iterate through set bits in rax (active positions)
// r12 contains follow pointer - no stack access needed!
; ->follow_loop:
; test rax, rax
; jz ->follow_done
// Get lowest set bit position using BSF
; bsf rsi, rax // rsi = position of lowest set bit
; or rdi, [r12 + rsi*8] // reachable |= follow[position] (r12 = follow!)
; blsr rax, rax // Clear lowest set bit (rax &= rax - 1)
; jmp ->follow_loop
; ->follow_done:
// Now rdi = reachable (positions that can be reached)
// state = !reachable | mask[byte]
; mov r11, rdi // r11 = reachable
; not r11 // r11 = !reachable
; movzx eax, BYTE [r14 + rcx] // byte = input[pos]
; or r11, [rbx + rax*8] // state |= mask[byte]
// Check for match - accept is in r13, no stack access!
; mov rax, r11
; or rax, r13 // rax = state | accept
; cmp rax, -1
; jne ->found_in_loop
// Check if dead state (all 1s = no active positions)
; cmp r11, -1
; je ->inner_done
// Next byte
; inc rcx
; jmp ->inner_loop
; ->found_at_start:
// Match found at start position (after first byte)
; mov [rsp+8], r10 // last_match_start = start
; lea rax, [r10 + 1]
; mov [rsp+16], rax // last_match_end = start + 1
// Continue to find longer match
; lea rcx, [r10 + 1] // pos = start + 1
; jmp ->inner_loop
; ->found_in_loop:
// Match found at position rcx
; mov [rsp+8], r10 // last_match_start = start
; lea rax, [rcx + 1]
; mov [rsp+16], rax // last_match_end = pos + 1
// Continue to find longest match
; inc rcx
; jmp ->inner_loop
; ->inner_done:
// If we found a match, we're done (first match wins for unanchored)
; cmp QWORD [rsp+16], -1
; jne ->done
// Try next start position
; inc r10
; jmp ->start_loop
; ->done:
// Check if we have a match
; mov rdx, [rsp+16] // rdx = last_match_end
; cmp rdx, -1
; je ->no_match
// Pack result: (start << 32) | end
; mov rax, [rsp+8] // rax = last_match_start
; shl rax, 32 // rax = start << 32
; or rax, rdx // rax = (start << 32) | end
; jmp ->epilogue
; ->no_match:
; mov rax, -1
; ->epilogue:
; add rsp, 24 // Deallocate stack space
; pop r15
; pop r14
; pop r13
; pop r12
; pop rbx
);
// Platform-specific epilogue
#[cfg(target_os = "windows")]
dynasm!(ops
; .arch x64
; pop rsi
; pop rdi
; ret
);
#[cfg(not(target_os = "windows"))]
dynasm!(ops
; .arch x64
; ret
);
offset
}
}