1,000+ ASIC Interview Questions: SystemVerilog, UVM & RTL

DescriptionQ409

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Q409DVASIC interview problem

Compile, program, and verify a bounded pattern matcher

TechniquesFirmwareUVMDynamic programming

DifficultyHard

TopicReference Models

LanguageSystemVerilog

Requirements4 checkpoints

Problem

Write the bounded pattern compiler, whole-record oracle, and transaction checks for literals, dot, and postfix star.

Type declarationSystemVerilog

typedef enum {
  PAT_OK, PAT_BAD_ARG, PAT_FULL, PAT_MMIO, PAT_TIMEOUT
} pat_status_t;
pat_status_t pat_program(const char *pattern, size_t length,
                         uint32_t timeout);

typedef struct packed {
  byte unsigned literal;
  bit any;
  bit star;
} pattern_token_t;

function automatic bit whole_record_match(
  input byte unsigned record[$],
  input pattern_token_t token[$]
);

Example input and output

Use this case to check your interpretation

Input

compile pattern="A.*B"; record="AXYB"

Output

shadow tokens=[literal A, dot-star, literal B]; whole-record match=1

Explanation

The star binds only to the preceding dot, which consumes XY while the leading A and trailing B anchor the entire record.

Requirements (4)

Reject a leading or repeated star, patterns above 48 bytes, and more than 24 compiled tokens before MMIO; an empty pattern is a valid committed program.
Use canonical token encoding, zero unused shadow slots, issue a release barrier, and preserve the active program after rejected commit, bus error, or timeout.
Build an independent prefix table for whole-record matching where star repeats only its preceding literal or dot zero or more times.
Enforce command and frame error priority, bounded responses, stable stalls, silent abort, and reset that clears both active and shadow configurations.