The CFG allows us to do layout optimization in the compiler. Furthermore, it allows further branch optimization.
The LHS and RHS are of SmallString and StringRef, respectively. We can safely use operator==(StringRef, SringRef) with one implicit conversion from SmallString to StringRef.
BasicBlockSections must enforce placing the entry block at the beginning of the function regardless of the basic block sections profile.
Port CodeGenPrepare to new pass manager and dependency BasicBlockSectionsProfileReader Fixes: #75380 Co-authored-by: Krishna-13-cyber <84722531+Krishna-13-cyber@users.noreply.github.com>
Revert e0c554ad87d18dcbfcb9b6485d0da800ae1338d1 "Port CodeGenPrepare to new pass manager (and BasicBlockSectionsProfil… (#75380)" Revert #75380 and #77054 as they were breaking EXPENSIVE_CHECKS buildbots: https://lab.llvm.org/buildbot/#/builders/104
Port CodeGenPrepare to new pass manager and dependency BasicBlockSectionsProfileReader Fixes: #64560 Co-authored-by: Krishna-13-cyber <84722531+Krishna-13-cyber@users.noreply.github.com>
This patch replaces uses of StringRef::{starts,ends}with with
StringRef::{starts,ends}_with for consistency with
std::{string,string_view}::{starts,ends}_with in C++20.
I'm planning to deprecate and eventually remove
StringRef::{starts,ends}with.
https://github.com/llvm/llvm-project/commit/28b912687900bc0a67cd61c374fce296b09963c4 introduced the path cloning format in the basic-block-sections profile. This PR validates and applies path clonings. A path cloning is valid if all of these conditions hold: 1. All bb ids in the path are mapped to existing blocks. 2. Each two consecutive bb ids in the path have a successor relationship in the CFG. 3. The path does not include a block with indirect branches, except possibly as the last block. Applying a path cloning involves cloning all blocks in the path (except the first one) and setting up their branches. Once all clonings are applied, the cluster information is used to guide block layout in the modified function.
Following up on prior RFC (https://lists.llvm.org/pipermail/llvm-dev/2020-September/145357.html) we can now improve above our highly-optimized basic-block-sections binary (e.g., 2% for clang) by applying path cloning. Cloning can improve performance by reducing taken branches. This patch prepares the profile format for applying cloning actions. The basic block cloning profile format extends the basic block sections profile in two ways. 1. Specifies the cloning paths with a 'p' specifier. For example, `p 1 4 5` specifies that blocks with BB ids 4 and 5 must be cloned along the edge 1 --> 4. 2. For each cloned block, it will appear in the cluster info as `<bb_id>.<clone_id>` where `clone_id` is the id associated with this clone. For example, the following profile specifies one cloned block (2) and determines its cluster position as well. ``` f foo p 1 2 c 0 1 2.1 3 2 5 ``` This patch keeps backward-compatibility (retains the behavior for old profile formats). This feature is only introduced for profile version >= 1.