ea2e66aa8b
llvm.is.constant (and therefore Clang's __builtin_constant_p()) need to report undefined values as non-constant or future DCE choices end up making no sense. This was encountered while building the Linux kernel which uses __builtin_constant_p() while trying to evaluate if it is safe to use a compile-time constant resolution for string lengths or if it must kick over to a full runtime call to strlen(). Obviously an undefined variable cannot be known at compile-time, so __builtin_constant_p() needs to return false. This change will also mean that Clang will match GCC's behavior under the same conditions. Fixes #130649
The LLVM Compiler Infrastructure
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.
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