forked from OSchip/llvm-project
2edcde00cb
Early revisions of the VR4300 have a hardware bug where two consecutive multiplications can produce an incorrect result in the second multiply. This revision adds the `-mfix4300` flag to llvm (and clang) which, when passed, provides a software fix for this issue. More precise description of the "mulmul" bug: ``` mul.[s,d] fd,fs,ft mul.[s,d] fd,fs,ft or [D]MULT[U] rs,rt ``` When the above sequence is executed by the CPU, if at least one of the source operands of the first mul instruction happens to be `sNaN`, `0` or `Infinity`, then the second mul instruction may produce an incorrect result. This can happen both if the two mul instructions are next to each other and if the first one is in a delay slot and the second is the first instruction of the branch target. Description of the fix: This fix adds a backend pass to llvm which scans for mul instructions in each basic block and inserts a nop whenever the following conditions are met: - The current instruction is a single or double-precision floating-point mul instruction. - The next instruction is either a mul instruction (any kind) or a branch instruction. Differential Revision: https://reviews.llvm.org/D116238 |
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| CMakeLists.txt | ||
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| README.txt | ||
README.txt
//===----------------------------------------------------------------------===// // C Language Family Front-end //===----------------------------------------------------------------------===// Welcome to Clang. This is a compiler front-end for the C family of languages (C, C++, Objective-C, and Objective-C++) which is built as part of the LLVM compiler infrastructure project. Unlike many other compiler frontends, Clang is useful for a number of things beyond just compiling code: we intend for Clang to be host to a number of different source-level tools. One example of this is the Clang Static Analyzer. If you're interested in more (including how to build Clang) it is best to read the relevant web sites. Here are some pointers: Information on Clang: http://clang.llvm.org/ Building and using Clang: http://clang.llvm.org/get_started.html Clang Static Analyzer: http://clang-analyzer.llvm.org/ Information on the LLVM project: http://llvm.org/ If you have questions or comments about Clang, a great place to discuss them is on the Clang development mailing list: http://lists.llvm.org/mailman/listinfo/cfe-dev If you find a bug in Clang, please file it in the LLVM bug tracker: http://llvm.org/bugs/