[cfe-dev] Question about Clang codegen tests

[Diogo Sampaio via cfe-dev]

Hi, 
see if this helps you tu understand the test it self: [ https://llvm.org/docs/CommandGuide/FileCheck.html | https://llvm.org/docs/CommandGuide/FileCheck.html ] 
And once you have a C/C++ input test file with a RUN: command on it, the test commands to check the result usually can be generated with the llvm-project/llvm/utils/update_cc_test_checks.py script. 
cheers 


Diogo Sampaio 
Senior Compiler Engineer • Kalray 
dsampaio at kalrayinc.com • [ https://www.kalrayinc.com/ | www.kalrayinc.com ] 

[ https://www.kalrayinc.com/ |   ] 

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From: "cfe-dev" <cfe-dev at lists.llvm.org> 
To: "cfe-dev" <cfe-dev at lists.llvm.org> 
Sent: Thursday, November 25, 2021 11:54:27 AM 
Subject: [cfe-dev] Question about Clang codegen tests 

Hello, everyone! 

I'm a newcomer, and want to make some contributions to the LLVM community. Is here the right place to reach out for help? Please forgive me if I did things wrong, as I'm unfamiliar with the LLVM workflow :-) 

So a few days ago I noticed an issue in the bugzilla: [ https://bugs.llvm.org/show_bug.cgi?id=52444 | https://bugs.llvm.org/show_bug.cgi?id=52444 ] , I thought it would be suitable for me to work on. But now I run into some problems: 

* What is meaning of the capitalized words in tests comments? 
For example, in `llvm-project/clang/test/CodeGen/builtins-elementwise-math.c`: 
``` 
// RUN: %clang_cc1 -triple x86_64-apple-darwin %s -emit-llvm -disable-llvm-passes -o - | FileCheck %s 
// CHECK-LABEL: define void @test_builtin_elementwise_abs( 
// CHECK: [[F1:%.+]] = load float, float* %f1.addr, align 4 
// CHECK-NEXT: call float @llvm.fabs.f32(float [[F1]]) 
``` 
What do `RUN`, `CHECK` mean? I can guess they are some test instructions, so I briefly look through the docs, but I can't find anything useful :-( I'm sorry but the docs are so much, it's hard to find something I actually don't know what is. 

* How can I write my own test for codegen? 
The actual code part is not that hard, problems came in when I want to write some tests. The fact is that I'm unfamiliar with LLVM IR, so I don't know how to write the expected output... 

Thanks so much for people who offer me help! 

Best regards, 
Jun Zhang 



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