forked from OSchip/llvm-project
f19b0c7f6b
Frequently you you want a bitmask consisting of a specified
number of 1s, either at the beginning or end of a word.
The naive way to do this is to write
template<typename T>
T leadingBitMask(unsigned N) {
return (T(1) << N) - 1;
}
but using this function you cannot produce a word with every
bit set to 1 (i.e. leadingBitMask<uint8_t>(8)) because left
shift is undefined when N is greater than or equal to the
number of bits in the word.
This patch provides an efficient, branch-free implementation
that works for all values of N in [0, CHAR_BIT*sizeof(T)]
Differential Revision: https://reviews.llvm.org/D32212
llvm-svn: 300710
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| Analysis | ||
| AsmParser | ||
| Bitcode | ||
| CodeGen | ||
| DebugInfo | ||
| ExecutionEngine | ||
| IR | ||
| LineEditor | ||
| Linker | ||
| MC | ||
| MI | ||
| Object | ||
| ObjectYAML | ||
| Option | ||
| ProfileData | ||
| Support | ||
| Target | ||
| Transforms | ||
| XRay | ||
| CMakeLists.txt | ||