LDC Lit-based testsuite

This page describes the Lit-based test suite used for testing LDC.

Lit

Lit is a tool created by the LLVM developers to run compiler tests, written in Python.
Read about it from the horse's mouth: LLVM Blog: 'lit' it.
Lit is an important piece of LLVM's Testing Infrastructure.

LDC uses the Python package as available from https://pypi.python.org/pypi/lit , which can be best installed using Python's pip.

The rest of this page will describe important functionality of the testsuite. It is very instructive to look at LLVM/Clang/LDC tests to see how different kind of tests can be constructed!

FileCheck

FileCheck is an LLVM tool that reads a file passed as argument and checks whether the input received from stdin corresponds to what that file says it should look like. Confusing? An example:

   FileCheck test.d < test.ll

That command loads FileCheck with file test.d. That file contains directives for FileCheck (starting with // CHECK, telling it what to look for in stdin. The directive // CHECK: LDC is awesome will check that "LDC is awesome" appears in stdin. FileCheck will succeed when all checks are satisfied.

A typical test case does:

• Run LDC with some commandline flags and a D input file, and have it output LLVM IR to a temporary file.
• Run FileCheck with the D input file as parameter, passing the temporary LLVM IR file through stdin

A simple test case example

To add a test case to the testsuite, all you have to do is create a file inside a subdirectory of the tests directory (not the d2 subdirectory!).

Let's say we created a file tests/codegen/attr_fastmath.d:

// RUN: %ldc -O0 -release -c -output-ll -of=%t.ll %s && FileCheck %s < %t.ll

import ldc.attributes;

@fastmath
double foo(double a, double b)
{
// CHECK: fmul fast
    auto c += a * b;
}

More complicated example

// Tests @target attribute for x86

// REQUIRES: atleast_llvm307
// REQUIRES: target_X86

// RUN: %ldc -O -c -mcpu=i386 -mtriple i386-linux-gnu -output-ll -of=%t.ll %s && FileCheck %s --check-prefix LLVM < %t.ll
// RUN: %ldc -O -c -mcpu=i386 -mtriple i386-linux-gnu -output-s -of=%t.s %s && FileCheck %s  --check-prefix ASM < %t.s

import ldc.attributes;

// LLVM-LABEL: define{{.*}} void @{{.*}}foo
// ASM-LABEL: _D15attr_target_x863fooFPfPffZv:
void foo(float *A, float* B, float K) {
    for (int i = 0; i < 128; ++i)
        A[i] *= B[i] + K;
// ASM-NOT: addps
}

// LLVM-LABEL: define{{.*}} void @{{.*}}foo_sse
// LLVM-SAME: #[[SSE:[0-9]+]]
// ASM-LABEL: _D15attr_target_x867foo_sseFPfPffZv:
@(target("sse"))
void foo_sse(float *A, float* B, float K) {
    for (int i = 0; i < 128; ++i)
        A[i] *= B[i] + K;
// ASM: addps
}

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