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cosmopolitan/libc/nexgen32e/bsr.h

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Initial import
2020-06-15 14:18:57 +00:00
#ifndef COSMOPOLITAN_LIBC_NEXGEN32E_BSR_H_
#define COSMOPOLITAN_LIBC_NEXGEN32E_BSR_H_
#if !(__ASSEMBLER__ + __LINKER__ + 0)
COSMOPOLITAN_C_START_
Add x86_64-linux-gnu emulator I wanted a tiny scriptable meltdown proof way to run userspace programs and visualize how program execution impacts memory. It helps to explain how things like Actually Portable Executable works. It can show you how the GCC generated code is going about manipulating matrices and more. I didn't feel fully comfortable with Qemu and Bochs because I'm not smart enough to understand them. I wanted something like gVisor but with much stronger levels of assurances. I wanted a single binary that'll run, on all major operating systems with an embedded GPL barrier ZIP filesystem that is tiny enough to transpile to JavaScript and run in browsers too. https://justine.storage.googleapis.com/emulator625.mp4
2020-08-25 11:23:25 +00:00
/*
* BIT SCANNING 101
* ctz(𝑥) 31^clz(𝑥) clz(𝑥)
* uint32 𝑥 bsf(𝑥) tzcnt(𝑥) ffs(𝑥) bsr(𝑥) lzcnt(𝑥)
* 0x00000000 wut 32 0 wut 32
* 0x00000001 0 0 1 0 31
* 0x80000001 0 0 1 31 0
* 0x80000000 31 31 32 31 0
* 0x00000010 4 4 5 4 27
* 0x08000010 4 4 5 27 4
* 0x08000000 27 27 28 27 4
* 0xffffffff 0 0 1 31 0
*/
Initial import
2020-06-15 14:18:57 +00:00
Fix some example code
2021-08-10 20:38:27 +00:00
int bsr(int) pureconst;
int bsrl(long) pureconst;
int bsrll(long long) pureconst;
int bsrmax(uintmax_t) pureconst;
Add x86_64-linux-gnu emulator I wanted a tiny scriptable meltdown proof way to run userspace programs and visualize how program execution impacts memory. It helps to explain how things like Actually Portable Executable works. It can show you how the GCC generated code is going about manipulating matrices and more. I didn't feel fully comfortable with Qemu and Bochs because I'm not smart enough to understand them. I wanted something like gVisor but with much stronger levels of assurances. I wanted a single binary that'll run, on all major operating systems with an embedded GPL barrier ZIP filesystem that is tiny enough to transpile to JavaScript and run in browsers too. https://justine.storage.googleapis.com/emulator625.mp4
2020-08-25 11:23:25 +00:00
Improve performance of bitscanning intrinsics This change helps spectre more intelligently plan execution, by working around false output dependencies, impacting ops like popcnt bsr and bsf
2021-06-15 13:24:46 +00:00
#if defined(__GNUC__) && defined(__x86_64__) && !defined(__STRICT_ANSI__)
#define bsr(u) \
({ \
unsigned BiTs; \
asm("bsr\t%0,%0" : "=r"(BiTs) : "0"((unsigned)(u)) : "cc"); \
BiTs; \
})
#define bsrl(u) \
({ \
unsigned long BiTs; \
asm("bsr\t%0,%0" : "=r"(BiTs) : "0"((unsigned long)(u)) : "cc"); \
(unsigned)BiTs; \
})
#define bsrll(u) bsrl(u)
Add chibicc This program popped up on Hacker News recently. It's the only modern compiler I've ever seen that doesn't have dependencies and is easily modified. So I added all of the missing GNU extensions I like to use which means it might be possible soon to build on non-Linux and have third party not vendor gcc binaries.
2020-12-05 20:20:41 +00:00
#endif
Initial import
2020-06-15 14:18:57 +00:00
COSMOPOLITAN_C_END_
#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
#endif /* COSMOPOLITAN_LIBC_NEXGEN32E_BSR_H_ */
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