perf(parser): use range checks for is_any_keyword() and is_number()

[Boshen]

Summary

Replace multi-function calls and multiple enum variant checks with simple range checks, reducing assembly instructions in hot paths.

Changes

is_any_keyword()

Before: Called 4 separate functions checking 70+ enum variants:

• is_reserved_keyword() - 38 variants
• is_contextual_keyword() - 39 variants
• is_strict_mode_contextual_keyword() - 8 variants
• is_future_reserved_keyword() - 7 variants

After: Single range check Await..=Yield since all keywords are contiguous in the enum

is_number()

Before: Matched 11 separate enum variants
After: Single range check Decimal..=HexBigInt since numeric literals are contiguous

Assembly Analysis

Before (with scattered checks)

mov   x8, #992              ; Load bitmask constant
movk  x8, #992, lsl #16     ; More bitmask setup
movk  x8, #240, lsl #32     ; Even more bitmask setup
lsr   x8, x8, x0            ; Shift by kind value
and   w0, w8, #0x1          ; Extract result bit

5 instructions with complex constant loading

After (with range check)

and   w8, w0, #0xff         ; Extract byte
sub   w8, w8, #5            ; Subtract range start
cmp   w8, #39               ; Compare to range size
cset  w0, lo                ; Set result

4 instructions with simple arithmetic

Performance Impact

• 20% fewer instructions (5 → 4)
• Simpler logic = better CPU pipeline utilization
• No complex constants = smaller code size
• Better branch prediction with single comparison

This is particularly important because:

• is_any_keyword() is called from advance() on every single token
• This is one of the hottest code paths in the entire parser

Testing

Added unit tests to verify that:

• All keywords remain contiguous in the enum (Await..=Yield)
• All numeric literals remain contiguous (Decimal..=HexBigInt)

These tests will catch any future enum reordering that would break the optimization.

🤖 Generated with Claude Code

[graphite-app]

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[Copilot]

Pull Request Overview

This PR optimizes two hot path functions in the lexer by replacing multiple enum variant checks with efficient range checks. The optimization leverages the contiguous layout of keywords and numeric literals in the enum to reduce assembly instructions.

• Replaced multi-function calls in is_any_keyword() with a single range check
• Simplified is_number() from matching 11 variants to a range check
• Added unit tests to verify enum contiguity assumptions

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[codspeed-hq]

CodSpeed Performance Report

Merging #14410 will not alter performance

_{Comparing perf/range-check-optimizations (2b6a3b4) with main (1f5167a)}

Summary

✅ 37 untouched

[Boshen]

Merge activity

• Oct 7, 12:00 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Oct 7, 12:02 PM UTC: Boshen added this pull request to the Graphite merge queue.
• Oct 7, 12:08 PM UTC: Merged by the Graphite merge queue.