Mordante added a comment. In D88363#2319242 <https://reviews.llvm.org/D88363#2319242>, @bdf wrote:
> In D88363#2319157 <https://reviews.llvm.org/D88363#2319157>, @jmorse wrote: > >> In D88363#2317241 <https://reviews.llvm.org/D88363#2317241>, @Mordante wrote: >> >>> Can you explain the kind of issues you're having? >> >> At the shallowest level, our -O1 produces different IR and fails the test, >> which is more or less our problem; however my understanding is that tests in >> the LLVM project / subprojects should aim to test as little amount of code >> as possible. Relying on all of -O1 makes it a brittle test -- changes to any >> optimisation pass enabled in -O1 could cause this test to fail spuriously. >> >> Instead, I believe the test should be in two parts: >> >> - One checking clang produces the correct /unoptimised/ IR output >> - One or more checking that the consuming IR passes do-the-right-thing > > As I see, the intent of the test is not so much to verify a certain expected > output, but more to verify that two styles of likelihood hints in C code > produce the same code structure and branch weights. Theses styles are > likely/unlikely-annotations, and use of __builtin_expect in the if condition. > But the processing of these two is quite different: > > - for likely/unlikely annotations, branch weights are added immediately in > the initial CodeGen > - __builtin_expect is first translated straightforward to an expect > intrinsic, then processed by a later lower-expect pass > > To make the test less brittle, would it be possible to explicitly select only > the optimization passes that are needed? Indeed verifying the output of the likelihood attributes against `__builtin_expect` is exactly what's required. But I think I can make the test less brittle by using the following command. This only runs the lower expect pass, which lowers the `__builtin_expect`. `RUN: %clang_cc1 -O1 -disable-llvm-passes -emit-llvm %s -o - -triple=x86_64-linux-gnu | opt --lower-expect -S | FileCheck %s` I'll work on a patch to solve the issue. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D88363/new/ https://reviews.llvm.org/D88363 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
