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2d36a55f0e
We treat bitwise 'not' as a special operation and try not to reduce its all-ones mask. Presumably, this is because a 'not' may be cheaper than a generic 'xor' or it may get folded into another logic op if the target has those. However, if we can remove a logic instruction by changing the xor's constant mask value, that should always be a win. Note that the IR version of SimplifyDemandedBits() does not treat 'not' as a special-case currently (although that's marked with a FIXME). So if you run this IR through -instcombine, you should get the same end result. I'm hoping to add a different backend transform that will expose this problem though, so I need to solve this first. Differential Revision: https://reviews.llvm.org/D27356 llvm-svn: 288676 |
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Analysis | ||
AsmParser | ||
Bitcode | ||
CodeGen | ||
DebugInfo | ||
Demangle | ||
ExecutionEngine | ||
Fuzzer | ||
IR | ||
IRReader | ||
LibDriver | ||
LineEditor | ||
Linker | ||
LTO | ||
MC | ||
Object | ||
ObjectYAML | ||
Option | ||
Passes | ||
ProfileData | ||
Support | ||
TableGen | ||
Target | ||
Transforms | ||
CMakeLists.txt | ||
LLVMBuild.txt |