ISPC Lit Tests

ISPC Lit Tests

A concise guide for writing lit tests for the ISPC. These tests ensure compiler correctness, verify generated code, and prevent regressions.

When to Use Lit Tests

Use lit tests when validating:

• Compiler output — LLVM IR, assembly, or AST.
• Diagnostics — warnings, errors, or other emitted messages.
• Platform behavior — verifying cross-platform or target-specific differences.
• Regression coverage — reproducing and locking fixes for known compiler issues.

Core Guidelines

Always Use --nowrap

Prevents line wrapping in compiler output for consistent FileCheck matching:

// RUN: %{ispc} %s --target=host --nowrap --emit-llvm-text -o - | FileCheck %s

Use --nostdlib When Not Testing Library Code

Simplifies test output and avoids unrelated symbols:

// RUN: %{ispc} %s --target=host --nostdlib --nowrap -o - | FileCheck %s

Avoid export Unless Testing It

export functions generate both masked and unmasked IR — doubling the verification effort.

// Preferred
void foo() { ... }