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std.mem: implement RVV indexOfSentinel optimization

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David Rubin 2025-07-30 15:18:30 -07:00
parent fbafbd4262
commit d6e3fdaad9
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1 changed files with 49 additions and 0 deletions
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49
lib/std/mem.zig
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@ -1156,6 +1156,55 @@ pub fn findSentinel(comptime T: type, comptime sentinel: T, p: [*:sentinel]const
i += block_len;
}
},
.riscv64 => if (comptime builtin.cpu.has(.riscv, .v) and switch (@bitSizeOf(T)) {
8, 16, 32, 64 => true,
else => false,
}) {
const clobber: std.builtin.assembly.Clobbers = .{
.x11 = true, // a1
.x12 = true, // a2
.x13 = true, // a3
.x14 = true, // a4
.v0 = true,
.v1 = true,
.v2 = true,
.v3 = true,
.v4 = true,
.v5 = true,
.v6 = true,
.v7 = true,
.v8 = true,
.v9 = true,
.v10 = true,
.v11 = true,
.v12 = true,
.v13 = true,
.v14 = true,
.v15 = true,
.v16 = true,
};
return asm (
\\ mv a3, %[ptr] # Save start
\\ vsetvli a1, zero, e%[size], m8, ta, ma # Vector of bytes of maximum length
\\
\\1:
\\ vle%[size]ff.v v8, (a3) # Load bytes
\\ li a1, %[sentinel] # Load sentinel into register
\\ vmseq.vx v0, v8, a1 # Set v0[i] where v8[i] = sentinel
\\ csrr a1, vl # Get bytes read
\\ vfirst.m a2, v0 # Find first set bit
\\ add a3, a3, a1 # Bump pointer
\\ bltz a2, 1b # Not found?
\\
\\ add a4, %[ptr], a1 # Sum start + bump
\\ add a3, a3, a2 # Add index
\\ sub %[result], a3, a4 # Subtract start address + bump
: [result] "=r" (-> usize),
: [ptr] "r" (p),
[sentinel] "i" (sentinel),
[size] "X" (@bitSizeOf(T)),
: clobber);
},
else => {},
}
}