[InstCombine] Fix miscompilation in `sinkNotIntoLogicalOp` (#142727)
Consider the following case:
```
define i1 @src(i8 %x) {
%cmp = icmp slt i8 %x, -1
%not1 = xor i1 %cmp, true
%or = or i1 %cmp, %not1
%not2 = xor i1 %or, true
ret i1 %not2
}
```
`sinkNotIntoLogicalOp(%or)` calls `freelyInvert(%cmp,
/*IgnoredUser=*/%or)` first. However, as `%cmp` is also used by `Op1 =
%not1`, the RHS of `%or` is set to `%cmp.not = xor i1 %cmp, true`. Thus
`Op1` is out of date in the second call to `freelyInvert`. Similarly,
the second call may change `Op0`. According to the analysis above, I
decided to avoid this fold when one of the operands is also a user of
the other.
Closes https://github.com/llvm/llvm-project/issues/142518.
Welcome to the LLVM project!
This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.
The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.
C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.
Other components include: the libc++ C++ standard library, the LLD linker, and more.
Consult the Getting Started with LLVM page for information on building and running LLVM.
For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.
Join the LLVM Discourse forums, Discord chat, LLVM Office Hours or Regular sync-ups.
The LLVM project has adopted a code of conduct for participants to all modes of communication within the project.