ISPC Lit Test Assistant FAQs

Question 1

What is the benefit of using --nowrap in ISPC lit tests?

Accepted Answer

The --nowrap flag prevents the ISPC compiler from wrapping long lines of output, which ensures that FileCheck can match patterns consistently regardless of the environment or terminal settings.

Question 2

How can I make my ISPC tests portable across different architectures?

Accepted Answer

Use named patterns like [[WIDTH]] and [[TYPE]] in your CHECK lines instead of hardcoding specific vector sizes or variable names, which can vary between LLVM versions and OS targets.

Question 3

How do I test a specific optimization pass in ISPC?

Accepted Answer

You can use the --debug-phase flag (e.g., --debug-phase=325:325) to dump the IR at a specific stage of the compilation process and verify the output of that specific pass.

Question 4

When should I use 'export' in a test function?

Accepted Answer

Avoid using 'export' unless you are specifically testing export behavior. Exported functions generate both masked and unmasked IR, which doubles the verification effort and clutters the test output.

Question 5

How are regression tests typically named in ISPC?

Accepted Answer

Regression tests should be named using their GitHub issue number (e.g., 1234.ispc) to maintain a clear link between the bug and the verification test.

ISPC Lit Test Assistant

Key Features

Use Cases

ISPC Lit Test Assistant

Key Features

Use Cases