04a309dd0b
Summary: The patch is not ready yet and is here to discuss a few options: - How do we customize the implementation? (i.e. how to define `kRepMovsBSize`), - How do we specify custom compilation flags? (We'd need `-fno-builtin-memcpy` to be passed in), - How do we build? We may want to test in debug but build the libc with `-march=native` for instance, - Clang has a brand new builtin `__builtin_memcpy_inline` which makes the implementation easy and efficient, but: - If we compile with `gcc` or `msvc` we can't use it, resorting on less efficient code generation, - With gcc we can use `__builtin_memcpy` but then we'd need a postprocess step to check that the final assembly do not contain call to `memcpy` (unlikely but allowed), - For msvc we'd need to resort on the compiler optimization passes. Reviewers: sivachandra, abrachet Subscribers: mgorny, MaskRay, tschuett, libc-commits, courbet Tags: #libc-project Differential Revision: https://reviews.llvm.org/D74397
30 lines
777 B
C++
30 lines
777 B
C++
#include <cstdio>
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#include <cstdlib>
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// This file is instantiated by CMake.
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// DEFINITIONS below is replaced with a set of lines like so:
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// #ifdef __SSE2__
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// "SSE2",
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// #endif
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//
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// This allows for introspection of compiler definitions.
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// The output of the program is a single line of semi colon separated feature
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// names.
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// MSVC is using a different set of preprocessor definitions for
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// SSE and SSE2, see _M_IX86_FP in
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// https://docs.microsoft.com/en-us/cpp/preprocessor/predefined-macros
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int main(int, char **) {
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const char *strings[] = {
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@DEFINITIONS@
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};
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const size_t size = sizeof(strings) / sizeof(strings[0]);
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for (size_t i = 0; i < size; ++i) {
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if (i)
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putchar(';');
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fputs(strings[i], stdout);
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}
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return EXIT_SUCCESS;
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}
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